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Dr. Laurie Starkey

Dr. Laurie Starkey

Stereochemistry

Slide Duration:

Table of Contents

I. Introduction to Organic Molecules
Introduction and Drawing Structures

49m 51s

Intro
0:00
Organic Chemistry
0:07
Organic
0:08
Inorganic
0:26
Examples of Organic Compounds
1:16
Review Some Chemistry Basics
5:23
Electrons
5:42
Orbitals (s,p,d,f)
6:12
Review Some Chemistry Basics
7:35
Elements & Noble Gases
7:36
Atom & Valance Shell
8:47
Review Some Chemistry Basics
11:33
Electronegative Elements
11:34
Which Is More Electronegative, C or N?
13:45
Ionic & Covalent Bonds
14:07
Ionic Bonds
14:08
Covalent Bonds
16:17
Polar Covalent Bonds
19:35
Polar Covalent Bonds & Electronegativities
19:37
Polarity of Molecules
22:56
Linear molecule
23:07
Bent Molecule
23:53
No Polar Bonds
24:21
Ionic
24:52
Line Drawings
26:36
Line Drawing Overview
26:37
Line Drawing: Example 1
27:12
Line Drawing: Example 2
29:14
Line Drawing: Example 3
29:51
Line Drawing: Example 4
30:34
Line Drawing: Example 5
31:21
Line Drawing: Example 6
32:41
Diversity of Organic Compounds
33:57
Diversity of Organic Compounds
33:58
Diversity of Organic Compounds, cont.
39:16
Diversity of Organic Compounds, cont.
39:17
Examples of Polymers
45:26
Examples of Polymers
45:27
Lewis Structures & Resonance

44m 25s

Intro
0:00
Lewis Structures
0:08
How to Draw a Lewis Structure
0:09
Examples
2:20
Lewis Structures
6:25
Examples: Lewis Structure
6:27
Determining Formal Charges
8:48
Example: Determining Formal Charges for Carbon
10:11
Example: Determining Formal Charges for Oxygen
11:02
Lewis Structures
12:08
Typical, Stable Bonding Patterns: Hydrogen
12:11
Typical, Stable Bonding Patterns: Carbon
12:58
Typical, Stable Bonding Patterns: Nitrogen
13:25
Typical, Stable Bonding Patterns: Oxygen
13:54
Typical, Stable Bonding Patterns: Halogen
14:16
Lewis Structure Example
15:17
Drawing a Lewis Structure for Nitric Acid
15:18
Resonance
21:58
Definition of Resonance
22:00
Delocalization
22:07
Hybrid Structure
22:38
Rules for Estimating Stability of Resonance Structures
26:04
Rule Number 1: Complete Octets
26:10
Rule Number 2: Separation of Charge
28:13
Rule Number 3: Negative and Positive Charges
30:02
Rule Number 4: Equivalent
31:06
Looking for Resonance
32:09
Lone Pair Next to a p Bond
32:10
Vacancy Next to a p Bond
33:53
p Bond Between Two Different Elements
35:00
Other Type of Resonance: Benzene
36:06
Resonance Example
37:29
Draw and Rank Resonance Forms
37:30
Acid-Base Reactions

1h 7m 46s

Intro
0:00
Acid-Base Reactions
0:07
Overview
0:08
Lewis Acid and Lewis Base
0:30
Example 1: Lewis Acid and Lewis Base
1:53
Example 2: Lewis Acid and Lewis Base
3:04
Acid-base Reactions
4:54
Bonsted-Lowry Acid and Bonsted-Lowry Base
4:56
Proton Transfer Reaction
5:36
Acid-Base Equilibrium
8:14
Two Acids in Competition = Equilibrium
8:15
Example: Which is the Stronger Acid?
8:40
Periodic Trends for Acidity
12:40
Across Row
12:41
Periodic Trends for Acidity
19:48
Energy Diagram
19:50
Periodic Trends for Acidity
21:28
Down a Family
21:29
Inductive Effects on Acidity
25:52
Example: Which is the Stronger Acid?
25:54
Other Electron-Withdrawing Group (EWG)
30:37
Inductive Effects on Acidity
32:55
Inductive Effects Decrease with Distance
32:56
Resonance Effects on Acidity
36:35
Examples of Resonance Effects on Acidity
36:36
Resonance Effects on Acidity
41:15
Small and Large Amount of Resonance
41:17
Acid-Base Example
43:10
Which is Most Acidic? Which is the Least Acidic?
43:12
Acid-Base Example
49:26
Which is the Stronger Base?
49:27
Acid-Base Example
53:58
Which is the Strongest Base?
53:59
Common Acids/Bases
1:00:45
Common Acids/Bases
1:00:46
Example: Determine the Direction of Equilibrium
1:04:51
Structures and Properties of Organic Molecules

1h 23m 35s

Intro
0:00
Orbitals and Bonding
0:20
Atomic Orbitals (AO)
0:21
Molecular Orbitals (MO)
1:46
Definition of Molecular Orbitals
1:47
Example 1: Formation of Sigma Bond and Molecular Orbitals
2:20
Molecular Orbitals (MO)
5:25
Example 2: Formation of Pi Bond
5:26
Overlapping E Levels of MO's
7:28
Energy Diagram
7:29
Electronic Transitions
9:18
Electronic Transitions
9:23
Hybrid Orbitals
12:04
Carbon AO
12:06
Hybridization
13:51
Hybrid Orbitals
15:02
Examples of Hybrid Orbitals
15:05
Example: Assign Hybridization
20:31
3-D Sketches
24:05
sp3
24:24
sp2
25:28
sp
27:41
3-D Sketches of Molecules
29:07
3-D Sketches of Molecules 1
29:08
3-D Sketches of Molecules 2
32:29
3-D Sketches of Molecules 3
35:36
3D Sketch
37:20
How to Draw 3D Sketch
37:22
Example 1: Drawing 3D Sketch
37:50
Example 2: Drawing 3D Sketch
43:04
Hybridization and Resonance
46:06
Example: Hybridization and Resonance
46:08
Physical Properties
49:55
Water Solubility, Boiling Points, and Intermolecular Forces
49:56
Types of 'Nonbonding' Interactions
51:47
Dipole-Dipole
52:37
Definition of Dipole-Dipole
52:39
Example: Dipole-Dipole Bonding
53:27
Hydrogen Bonding
57:14
Definition of Hydrogen Bonding
57:15
Example: Hydrogen Bonding
58:05
Van Der Waals/ London Forces
1:03:11
Van Der Waals/ London Forces
1:03:12
Example: Van Der Waals/ London Forces
1:04:59
Water Solubility
1:08:32
Water Solubility
1:08:34
Example: Water Solubility
1:09:05
Example: Acetone
1:11:29
Isomerism
1:13:51
Definition of Isomers
1:13:53
Constitutional Isomers and Example
1:14:17
Stereoisomers and Example
1:15:34
Introduction to Functional Groups
1:17:06
Functional Groups: Example, Abbreviation, and Name
1:17:07
Introduction to Functional Groups
1:20:48
Functional Groups: Example, Abbreviation, and Name
1:20:49
Alkane Structures

1h 13m 38s

Intro
0:00
Nomenclature of Alkanes
0:12
Nomenclature of Alkanes and IUPAC Rules
0:13
Examples: Nomenclature of Alkanes
4:38
Molecular Formula and Degrees of Unsaturation (DU)
17:24
Alkane Formula
17:25
Example: Heptane
17:58
Why '2n+2' Hydrogens?
18:35
Adding a Ring
19:20
Adding a p Bond
19:42
Example 1: Determine Degrees of Unsaturation (DU)
20:17
Example 2: Determine Degrees of Unsaturation (DU)
21:35
Example 3: Determine DU of Benzene
23:30
Molecular Formula and Degrees of Unsaturation (DU)
24:41
Example 4: Draw Isomers
24:42
Physical properties of Alkanes
29:17
Physical properties of Alkanes
29:18
Conformations of Alkanes
33:40
Conformational Isomers
33:42
Conformations of Ethane: Eclipsed and Staggered
34:40
Newman Projection of Ethane
36:15
Conformations of Ethane
40:38
Energy and Degrees Rotated Diagram
40:41
Conformations of Butane
42:28
Butane
42:29
Newman Projection of Butane
43:35
Conformations of Butane
44:25
Energy and Degrees Rotated Diagram
44:30
Cycloalkanes
51:26
Cyclopropane and Cyclobutane
51:27
Cyclopentane
53:56
Cycloalkanes
54:56
Cyclohexane: Chair, Boat, and Twist Boat Conformations
54:57
Drawing a Cyclohexane Chair
57:58
Drawing a Cyclohexane Chair
57:59
Newman Projection of Cyclohexane
1:02:14
Cyclohexane Chair Flips
1:04:06
Axial and Equatorial Groups
1:04:10
Example: Chair Flip on Methylcyclohexane
1:06:44
Cyclohexane Conformations Example
1:09:01
Chair Conformations of cis-1-t-butyl-4-methylcyclohexane
1:09:02
Stereochemistry

1h 40m 54s

Intro
0:00
Stereochemistry
0:10
Isomers
0:11
Stereoisomer Examples
1:30
Alkenes
1:31
Cycloalkanes
2:35
Stereoisomer Examples
4:00
Tetrahedral Carbon: Superimposable (Identical)
4:01
Tetrahedral Carbon: Non-Superimposable (Stereoisomers)
5:18
Chirality
7:18
Stereoisomers
7:19
Chiral
8:05
Achiral
8:29
Example: Achiral and Chiral
8:45
Chirality
20:11
Superimposable, Non-Superimposable, Chiral, and Achiral
20:12
Nomenclature
23:00
Cahn-Ingold-Prelog Rules
23:01
Nomenclature
29:39
Example 1: Nomenclature
29:40
Example 2: Nomenclature
31:49
Example 3: Nomenclature
33:24
Example 4: Nomenclature
35:39
Drawing Stereoisomers
36:58
Drawing (S)-2-bromopentane
36:59
Drawing the Enantiomer of (S)-2-bromopentane: Method 1
38:47
Drawing the Enantiomer of (S)-2-bromopentane: Method 2
39:35
Fischer Projections
41:47
Definition of Fischer Projections
41:49
Drawing Fischer Projection
43:43
Use of Fisher Projection: Assigning Configuration
49:13
Molecules with Two Chiral Carbons
51:49
Example A
51:42
Drawing Enantiomer of Example A
53:26
Fischer Projection of A
54:25
Drawing Stereoisomers, cont.
59:40
Drawing Stereoisomers Examples
59:41
Diastereomers
1:01:48
Drawing Stereoisomers
1:06:37
Draw All Stereoisomers of 2,3-dichlorobutane
1:06:38
Molecules with Two Chiral Centers
1:10:22
Draw All Stereoisomers of 2,3-dichlorobutane, cont.
1:10:23
Optical Activity
1:14:10
Chiral Molecules
1:14:11
Angle of Rotation
1:14:51
Achiral Species
1:16:46
Physical Properties of Stereoisomers
1:17:11
Enantiomers
1:17:12
Diastereomers
1:18:01
Example
1:18:26
Physical Properties of Stereoisomers
1:23:05
When Do Enantiomers Behave Differently?
1:23:06
Racemic Mixtures
1:28:18
Racemic Mixtures
1:28:21
Resolution
1:29:52
Unequal Mixtures of Enantiomers
1:32:54
Enantiomeric Excess (ee)
1:32:55
Unequal Mixture of Enantiomers
1:34:43
Unequal Mixture of Enantiomers
1:34:44
Example: Finding ee
1:36:38
Example: Percent of Composition
1:39:46
II. Understanding Organic Reactions
Nomenclature

1h 53m 47s

Intro
0:00
Cycloalkane Nomenclature
0:17
Cycloalkane Nomenclature and Examples
0:18
Alkene Nomenclature
6:28
Alkene Nomenclature and Examples
6:29
Alkene Nomenclature: Stereochemistry
15:07
Alkenes With Two Groups: Cis & Trans
15:08
Alkenes With Greater Than Two Groups: E & Z
18:26
Alkyne Nomenclature
24:46
Alkyne Nomenclature and Examples
24:47
Alkane Has a Higher Priority Than Alkyne
28:25
Alcohol Nomenclature
29:24
Alcohol Nomenclature and Examples
29:25
Alcohol FG Has Priority Over Alkene/yne
33:41
Ether Nomenclature
36:32
Ether Nomenclature and Examples
36:33
Amine Nomenclature
42:59
Amine Nomenclature and Examples
43:00
Amine Nomenclature
49:45
Primary, Secondary, Tertiary, Quaternary Salt
49:46
Aldehyde Nomenclature
51:37
Aldehyde Nomenclature and Examples
51:38
Ketone Nomenclature
58:43
Ketone Nomenclature and Examples
58:44
Aromatic Nomenclature
1:05:02
Aromatic Nomenclature and Examples
1:05:03
Aromatic Nomenclature, cont.
1:09:09
Ortho, Meta, and Para
1:09:10
Aromatic Nomenclature, cont.
1:13:27
Common Names for Simple Substituted Aromatic Compounds
1:13:28
Carboxylic Acid Nomenclature
1:16:35
Carboxylic Acid Nomenclature and Examples
1:16:36
Carboxylic Acid Derivatives
1:22:28
Carboxylic Acid Derivatives
1:22:42
General Structure
1:23:10
Acid Halide Nomenclature
1:24:48
Acid Halide Nomenclature and Examples
1:24:49
Anhydride Nomenclature
1:28:10
Anhydride Nomenclature and Examples
1:28:11
Ester Nomenclature
1:32:50
Ester Nomenclature
1:32:51
Carboxylate Salts
1:38:51
Amide Nomenclature
1:40:02
Amide Nomenclature and Examples
1:40:03
Nitrile Nomenclature
1:45:22
Nitrile Nomenclature and Examples
1:45:23
Chemical Reactions

51m 1s

Intro
0:00
Chemical Reactions
0:06
Reactants and Products
0:07
Thermodynamics
0:50
Equilibrium Constant
1:06
Equation
2:35
Organic Reaction
3:05
Energy vs. Progress of Rxn Diagrams
3:48
Exothermic Reaction
4:02
Endothermic Reaction
6:54
Estimating ΔH rxn
9:15
Bond Breaking
10:03
Bond Formation
10:25
Bond Strength
11:35
Homolytic Cleavage
11:59
Bond Dissociation Energy (BDE) Table
12:29
BDE for Multiple Bonds
14:32
Examples
17:35
Kinetics
20:35
Kinetics
20:36
Examples
21:49
Reaction Rate Variables
23:15
Reaction Rate Variables
23:16
Increasing Temperature, Increasing Rate
24:08
Increasing Concentration, Increasing Rate
25:39
Decreasing Energy of Activation, Increasing Rate
27:49
Two-Step Mechanisms
30:06
E vs. POR Diagram (2-step Mechanism)
30:07
Reactive Intermediates
33:03
Reactive Intermediates
33:04
Example: A Carbocation
35:20
Carbocation Stability
37:24
Relative Stability of Carbocation
37:25
Alkyl groups and Hyperconjugation
38:45
Carbocation Stability
41:57
Carbocation Stabilized by Resonance: Allylic
41:58
Carbocation Stabilized by Resonance: Benzylic
42:59
Overall Carbocation Stability
44:05
Free Radicals
45:05
Definition and Examples of Free Radicals
45:06
Radical Mechanisms
49:40
Example: Regular Arrow
49:41
Example: Fish-Hook Arrow
50:17
Free Radical Halogenation

26m 23s

Intro
0:00
Free Radical Halogenation
0:06
Free Radical Halogenation
0:07
Mechanism: Initiation
1:27
Mechanism: Propagation Steps
2:21
Free Radical Halogenation
5:33
Termination Steps
5:36
Example 1: Terminations Steps
6:00
Example 2: Terminations Steps
6:18
Example 3: Terminations Steps
7:43
Example 4: Terminations Steps
8:04
Regiochemistry of Free Radical Halogenation
9:32
Which Site/Region Reacts and Why?
9:34
Bromination and Rate of Reaction
14:03
Regiochemistry of Free Radical Halogenation
14:30
Chlorination
14:31
Why the Difference in Selectivity?
19:58
Allylic Halogenation
20:53
Examples of Allylic Halogenation
20:55
Substitution Reactions

1h 48m 5s

Intro
0:00
Substitution Reactions
0:06
Substitution Reactions Example
0:07
Nucleophile
0:39
Electrophile
1:20
Leaving Group
2:56
General Reaction
4:13
Substitution Reactions
4:43
General Reaction
4:46
Substitution Reaction Mechanisms: Simultaneous
5:08
Substitution Reaction Mechanisms: Stepwise
5:34
SN2 Substitution
6:21
Example of SN2 Mechanism
6:22
SN2 Kinetics
7:58
Rate of SN2
9:10
Sterics Affect Rate of SN2
9:12
Rate of SN2 (By Type of RX)
14:13
SN2: E vs. POR Diagram
17:26
E vs. POR Diagram
17:27
Transition State (TS)
18:24
SN2 Transition State, Kinetics
20:58
SN2 Transition State, Kinetics
20:59
Hybridization of TS Carbon
21:57
Example: Allylic LG
23:34
Stereochemistry of SN2
25:46
Backside Attack and Inversion of Stereochemistry
25:48
SN2 Summary
29:56
Summary of SN2
29:58
Predict Products (SN2)
31:42
Example 1: Predict Products
31:50
Example 2: Predict Products
33:38
Example 3: Predict Products
35:11
Example 4: Predict Products
36:11
Example 5: Predict Products
37:32
SN1 Substitution Mechanism
41:52
Is This Substitution? Could This Be an SN2 Mechanism?
41:54
SN1 Mechanism
43:50
Two Key Steps: 1. Loss of LG
43:53
Two Key Steps: 2. Addition of nu
45:11
SN1 Kinetics
47:17
Kinetics of SN1
47:18
Rate of SN1 (By RX type)
48:44
SN1 E vs. POR Diagram
49:49
E vs. POR Diagram
49:51
First Transition Stage (TS-1)
51:48
Second Transition Stage (TS-2)
52:56
Stereochemistry of SN1
53:44
Racemization of SN1 and Achiral Carbocation Intermediate
53:46
Example
54:29
SN1 Summary
58:25
Summary of SN1
58:26
SN1 or SN2 Mechanisms?
1:00:40
Example 1: SN1 or SN2 Mechanisms
1:00:42
Example 2: SN1 or SN2 Mechanisms
1:03:00
Example 3: SN1 or SN2 Mechanisms
1:04:06
Example 4: SN1 or SN2 Mechanisms
1:06:17
SN1 Mechanism
1:09:12
Three Steps of SN1 Mechanism
1:09:13
SN1 Carbocation Rearrangements
1:14:50
Carbocation Rearrangements Example
1:14:51
SN1 Carbocation Rearrangements
1:20:46
Alkyl Groups Can Also Shift
1:20:48
Leaving Groups
1:24:26
Leaving Groups
1:24:27
Forward or Reverse Reaction Favored?
1:26:00
Leaving Groups
1:29:59
Making poor LG Better: Method 1
1:30:00
Leaving Groups
1:34:18
Making poor LG Better: Tosylate (Method 2)
1:34:19
Synthesis Problem
1:38:15
Example: Provide the Necessary Reagents
1:38:16
Nucleophilicity
1:41:10
What Makes a Good Nucleophile?
1:41:11
Nucleophilicity
1:44:45
Periodic Trends: Across Row
1:44:47
Periodic Trends: Down a Family
1:46:46
Elimination Reactions

1h 11m 43s

Intro
0:00
Elimination Reactions: E2 Mechanism
0:06
E2 Mechanism
0:08
Example of E2 Mechanism
1:01
Stereochemistry of E2
4:48
Anti-Coplanar & Anti-Elimination
4:50
Example 1: Stereochemistry of E2
5:34
Example 2: Stereochemistry of E2
10:39
Regiochemistry of E2
13:04
Refiochemistry of E2 and Zaitsev's Rule
13:05
Alkene Stability
17:39
Alkene Stability
19:20
Alkene Stability Examples
19:22
Example 1: Draw Both E2 Products and Select Major
21:57
Example 2: Draw Both E2 Products and Select Major
25:02
SN2 Vs. E2 Mechanisms
29:06
SN2 Vs. E2 Mechanisms
29:07
When Do They Compete?
30:34
SN2 Vs. E2 Mechanisms
31:23
Compare Rates
31:24
SN2 Vs. E2 Mechanisms
36:34
t-BuBr: What If Vary Base?
36:35
Preference for E2 Over SN2 (By RX Type)
40:42
E1 Elimination Mechanism
41:51
E1 - Elimination Unimolecular
41:52
E1 Mechanism: Step 1
44:14
E1 Mechanism: Step 2
44:48
E1 Kinetics
46:58
Rate = k[RCI]
47:00
E1 Rate (By Type of Carbon Bearing LG)
48:31
E1 Stereochemistry
49:49
Example 1: E1 Stereochemistry
49:51
Example 2: E1 Stereochemistry
52:31
Carbocation Rearrangements
55:57
Carbocation Rearrangements
56:01
Product Mixtures
57:20
Predict the Product: SN2 vs. E2
59:58
Example 1: Predict the Product
1:00:00
Example 2: Predict the Product
1:02:10
Example 3: Predict the Product
1:04:07
Predict the Product: SN2 vs. E2
1:06:06
Example 4: Predict the Product
1:06:07
Example 5: Predict the Product
1:07:29
Example 6: Predict the Product
1:07:51
Example 7: Predict the Product
1:09:18
III. Alkanes, Alkenes, & Alkynes
Alkenes

36m 39s

Intro
0:00
Alkenes
0:12
Definition and Structure of Alkenes
0:13
3D Sketch of Alkenes
1:53
Pi Bonds
3:48
Alkene Stability
4:57
Alkyl Groups Attached
4:58
Trans & Cis
6:20
Alkene Stability
8:42
Pi Bonds & Conjugation
8:43
Bridgehead Carbons & Bredt's Rule
10:22
Measuring Stability: Hydrogenation Reaction
11:40
Alkene Synthesis
12:01
Method 1: E2 on Alkyl Halides
12:02
Review: Stereochemistry
16:17
Review: Regiochemistry
16:50
Review: SN2 vs. E2
17:34
Alkene Synthesis
18:57
Method 2: Dehydration of Alcohols
18:58
Mechanism
20:08
Alkene Synthesis
23:26
Alcohol Dehydration
23:27
Example 1: Comparing Strong Acids
26:59
Example 2: Mechanism for Dehydration Reaction
29:00
Example 3: Transform
32:50
Reactions of Alkenes

2h 8m 44s

Intro
0:00
Reactions of Alkenes
0:05
Electrophilic Addition Reaction
0:06
Addition of HX
2:02
Example: Regioselectivity & 2 Steps Mechanism
2:03
Markovnikov Addition
5:30
Markovnikov Addition is Favored
5:31
Graph: E vs. POR
6:33
Example
8:29
Example: Predict and Consider the Stereochemistry
8:30
Hydration of Alkenes
12:31
Acid-catalyzed Addition of Water
12:32
Strong Acid
14:20
Hydration of Alkenes
15:20
Acid-catalyzed Addition of Water: Mechanism
15:21
Hydration vs. Dehydration
19:51
Hydration Mechanism is Exact Reverse of Dehydration
19:52
Example
21:28
Example: Hydration Reaction
21:29
Alternative 'Hydration' Methods
25:26
Oxymercuration-Demercuration
25:27
Oxymercuration Mechanism
28:55
Mechanism of Oxymercuration
28:56
Alternative 'Hydration' Methods
30:51
Hydroboration-Oxidation
30:52
Hydroboration Mechanism
33:22
1-step (concerted)
33:23
Regioselective
34:45
Stereoselective
35:30
Example
35:58
Example: Hydroboration-Oxidation
35:59
Example
40:42
Example: Predict the Major Product
40:43
Synthetic Utility of 'Alternate' Hydration Methods
44:36
Example: Synthetic Utility of 'Alternate' Hydration Methods
44:37
Flashcards
47:28
Tips On Using Flashcards
47:29
Bromination of Alkenes
49:51
Anti-Addition of Br₂
49:52
Bromination Mechanism
53:16
Mechanism of Bromination
53:17
Bromination Mechanism
55:42
Mechanism of Bromination
55:43
Bromination: Halohydrin Formation
58:54
Addition of other Nu: to Bromonium Ion
58:55
Mechanism
1:00:08
Halohydrin: Regiochemistry
1:03:55
Halohydrin: Regiochemistry
1:03:56
Bromonium Ion Intermediate
1:04:26
Example
1:09:28
Example: Predict Major Product
1:09:29
Example Cont.
1:10:59
Example: Predict Major Product Cont.
1:11:00
Catalytic Hydrogenation of Alkenes
1:13:19
Features of Catalytic Hydrogenation
1:13:20
Catalytic Hydrogenation of Alkenes
1:14:48
Metal Surface
1:14:49
Heterogeneous Catalysts
1:15:29
Homogeneous Catalysts
1:16:08
Catalytic Hydrogenation of Alkenes
1:17:44
Hydrogenation & Pi Bond Stability
1:17:45
Energy Diagram
1:19:22
Catalytic Hydrogenation of Dienes
1:20:40
Hydrogenation & Pi Bond Stability
1:20:41
Energy Diagram
1:23:31
Example
1:24:14
Example: Predict Product
1:24:15
Oxidation of Alkenes
1:27:21
Redox Review
1:27:22
Epoxide
1:30:26
Diol (Glycol)
1:30:54
Ketone/ Aldehyde
1:31:13
Epoxidation
1:32:08
Epoxidation
1:32:09
General Mechanism
1:36:32
Alternate Epoxide Synthesis
1:37:38
Alternate Epoxide Synthesis
1:37:39
Dihydroxylation
1:41:10
Dihydroxylation
1:41:12
General Mechanism (Concerted Via Cycle Intermediate)
1:42:38
Ozonolysis
1:44:22
Ozonolysis: Introduction
1:44:23
Ozonolysis: Is It Good or Bad?
1:45:05
Ozonolysis Reaction
1:48:54
Examples
1:51:10
Example 1: Ozonolysis
1:51:11
Example
1:53:25
Radical Addition to Alkenes
1:55:05
Recall: Free-Radical Halogenation
1:55:15
Radical Mechanism
1:55:45
Propagation Steps
1:58:01
Atom Abstraction
1:58:30
Addition to Alkene
1:59:11
Radical Addition to Alkenes
1:59:54
Markovnivok (Electrophilic Addition) & anti-Mark. (Radical Addition)
1:59:55
Mechanism
2:01:03
Alkene Polymerization
2:05:35
Example: Alkene Polymerization
2:05:36
Alkynes

1h 13m 19s

Intro
0:00
Structure of Alkynes
0:04
Structure of Alkynes
0:05
3D Sketch
2:30
Internal and Terminal
4:03
Reductions of Alkynes
4:36
Catalytic Hydrogenation
4:37
Lindlar Catalyst
5:25
Reductions of Alkynes
7:24
Dissolving Metal Reduction
7:25
Oxidation of Alkynes
9:24
Ozonolysis
9:25
Reactions of Alkynes
10:56
Addition Reactions: Bromination
10:57
Addition of HX
12:24
Addition of HX
12:25
Addition of HX
13:36
Addition of HX: Mechanism
13:37
Example
17:38
Example: Transform
17:39
Hydration of Alkynes
23:35
Hydration of Alkynes
23:36
Hydration of Alkynes
26:47
Hydration of Alkynes: Mechanism
26:49
'Hydration' via Hydroboration-Oxidation
32:57
'Hydration' via Hydroboration-Oxidation
32:58
Disiamylborane
33:28
Hydroboration-Oxidation Cont.
34:25
Alkyne Synthesis
36:17
Method 1: Alkyne Synthesis By Dehydrohalogenation
36:19
Alkyne Synthesis
39:06
Example: Transform
39:07
Alkyne Synthesis
41:21
Method 2 & Acidity of Alkynes
41:22
Conjugate Bases
43:06
Preparation of Acetylide Anions
49:55
Preparation of Acetylide Anions
49:57
Alkyne Synthesis
53:40
Synthesis Using Acetylide Anions
53:41
Example 1: Transform
57:04
Example 2: Transform
1:01:07
Example 3: Transform
1:06:22
IV. Alcohols
Alcohols, Part I

59m 52s

Intro
0:00
Alcohols
0:11
Attributes of Alcohols
0:12
Boiling Points
2:00
Water Solubility
5:00
Water Solubility (Like Dissolves Like)
5:01
Acidity of Alcohols
9:39
Comparison of Alcohols Acidity
9:41
Preparation of Alkoxides
13:03
Using Strong Base Like Sodium Hydride
13:04
Using Redox Reaction
15:36
Preparation of Alkoxides
17:41
Using K°
17:42
Phenols Are More Acidic Than Other Alcohols
19:51
Synthesis of Alcohols, ROH
21:43
Synthesis of Alcohols from Alkyl Halides, RX (SN2 or SN1)
21:44
Synthesis of Alcohols, ROH
25:08
Unlikely on 2° RX (E2 Favored)
25:09
Impossible on 3° RX (E2) and Phenyl/Vinyl RX (N/R)
25:47
Synthesis of Alcohols, ROH
26:26
SN1 with H₂O 'Solvolysis' or 'Hydrolysis'
26:27
Carbocation Can Rearrange
29:00
Synthesis of Alcohols, ROH
30:08
Synthesis of Alcohols From Alkenes: Hydration
30:09
Synthesis of Alcohols From Alkenes: Oxidation/Diol
32:20
Synthesis of Alcohols, ROH
33:14
Synthesis of Alcohols From Ketones and Aldehydes
33:15
Organometallic Reagents: Preparation
37:03
Grignard (RMgX)
37:04
Organolithium (Rli)
40:03
Organometallic Reagents: Reactions
41:45
Reactions of Organometallic Reagents
41:46
Organometallic Reagents: Reactions as Strong Nu:
46:40
Example 1: Reactions as Strong Nu:
46:41
Example 2: Reactions as Strong Nu:
48:57
Hydride Nu:
50:52
Hydride Nu:
50:53
Examples
53:34
Predict 1
53:35
Predict 2
54:45
Examples
56:43
Transform
56:44
Provide Starting Material
58:18
Alcohols, Part II

45m 35s

Intro
0:00
Oxidation Reactions
0:08
Oxidizing Agents: Jones, PCC, Swern
0:09
'Jones' Oxidation
0:43
Example 1: Predict Oxidation Reactions
2:29
Example 2: Predict Oxidation Reactions
3:00
Oxidation Reactions
4:11
Selective Oxidizing Agents (PCC and Swern)
4:12
PCC (Pyridiniym Chlorochromate)
5:10
Swern Oxidation
6:05
General [ox] Mechanism
8:32
General [ox] Mechanism
8:33
Oxidation of Alcohols
10:11
Example 1: Oxidation of Alcohols
10:12
Example 2: Oxidation of Alcohols
11:20
Example 3: Oxidation of Alcohols
11:46
Example
13:09
Predict: PCC Oxidation Reactions
13:10
Tosylation of Alcohols
15:22
Introduction to Tosylation of Alcohols
15:23
Example
21:08
Example: Tosylation of Alcohols
21:09
Reductions of Alcohols
23:39
Reductions of Alcohols via SN2 with Hydride
24:22
Reductions of Alcohols via Dehydration
27:12
Conversion of Alcohols to Alkyl Halides
30:12
Conversion of Alcohols to Alkyl Halides via Tosylate
30:13
Conversion of Alcohols to Alkyl Halides
31:17
Using HX
31:18
Mechanism
32:09
Conversion of Alcohols to Alkyl Halides
35:43
Reagents that Provide LG and Nu: in One 'Pot'
35:44
General Mechanisms
37:44
Example 1: General Mechanisms
37:45
Example 2: General Mechanisms
39:25
Example
41:04
Transformation of Alcohols
41:05
V. Ethers, Thiols, Thioethers, & Ketones
Ethers

1h 34m 45s

Intro
0:00
Ethers
0:11
Overview of Ethers
0:12
Boiling Points
1:37
Ethers
4:34
Water Solubility (Grams per 100mL H₂O)
4:35
Synthesis of Ethers
7:53
Williamson Ether Synthesis
7:54
Example: Synthesis of Ethers
9:23
Synthesis of Ethers
10:27
Example: Synthesis of Ethers
10:28
Intramolecular SN2
13:04
Planning an Ether Synthesis
14:45
Example 1: Planning an Ether Synthesis
14:46
Planning an Ether Synthesis
16:16
Example 2: Planning an Ether Synthesis
16:17
Planning an Ether Synthesis
22:04
Example 3: Synthesize Dipropyl Ether
22:05
Planning an Ether Synthesis
26:01
Example 4: Transform
26:02
Synthesis of Epoxides
30:05
Synthesis of Epoxides Via Williamson Ether Synthesis
30:06
Synthesis of Epoxides Via Oxidation
32:42
Reaction of Ethers
33:35
Reaction of Ethers
33:36
Reactions of Ethers with HBr or HI
34:44
Reactions of Ethers with HBr or HI
34:45
Mechanism
35:25
Epoxide Ring-Opening Reaction
39:25
Epoxide Ring-Opening Reaction
39:26
Example: Epoxide Ring-Opening Reaction
42:42
Acid-Catalyzed Epoxide Ring Opening
44:16
Acid-Catalyzed Epoxide Ring Opening Mechanism
44:17
Acid-Catalyzed Epoxide Ring Opening
50:13
Acid-Catalyzed Epoxide Ring Opening Mechanism
50:14
Catalyst Needed for Ring Opening
53:34
Catalyst Needed for Ring Opening
53:35
Stereochemistry of Epoxide Ring Opening
55:56
Stereochemistry: SN2 Mechanism
55:57
Acid or Base Mechanism?
58:30
Example
1:01:03
Transformation
1:01:04
Regiochemistry of Epoxide Ring Openings
1:05:29
Regiochemistry of Epoxide Ring Openings in Base
1:05:30
Regiochemistry of Epoxide Ring Openings in Acid
1:07:34
Example
1:10:26
Example 1: Epoxide Ring Openings in Base
1:10:27
Example 2: Epoxide Ring Openings in Acid
1:12:50
Reactions of Epoxides with Grignard and Hydride
1:15:35
Reactions of Epoxides with Grignard and Hydride
1:15:36
Example
1:21:47
Example: Ethers
1:21:50
Example
1:27:01
Example: Synthesize
1:27:02
Thiols and Thioethers

16m 50s

Intro
0:00
Thiols and Thioethers
0:10
Physical Properties
0:11
Reactions Can Be Oxidized
2:16
Acidity of Thiols
3:11
Thiols Are More Acidic Than Alcohols
3:12
Synthesis of Thioethers
6:44
Synthesis of Thioethers
6:45
Example
8:43
Example: Synthesize the Following Target Molecule
8:44
Example
14:18
Example: Predict
14:19
Ketones

2h 18m 12s

Intro
0:00
Aldehydes & Ketones
0:11
The Carbonyl: Resonance & Inductive
0:12
Reactivity
0:50
The Carbonyl
2:35
The Carbonyl
2:36
Carbonyl FG's
4:10
Preparation/Synthesis of Aldehydes & Ketones
6:18
Oxidation of Alcohols
6:19
Ozonolysis of Alkenes
7:16
Hydration of Alkynes
8:01
Reaction with Hydride Nu:
9:00
Reaction with Hydride Nu:
9:01
Reaction with Carbon Nu:
11:29
Carbanions: Acetylide
11:30
Carbanions: Cyanide
14:23
Reaction with Carbon Nu:
15:32
Organometallic Reagents (RMgX, Rli)
15:33
Retrosynthesis of Alcohols
17:04
Retrosynthesis of Alcohols
17:05
Example
19:30
Example: Transform
19:31
Example
22:57
Example: Transform
22:58
Example
28:19
Example: Transform
28:20
Example
33:36
Example: Transform
33:37
Wittig Reaction
37:39
Wittig Reaction: A Resonance-Stabilized Carbanion (Nu:)
37:40
Wittig Reaction: Mechanism
39:51
Preparation of Wittig Reagent
41:58
Two Steps From RX
41:59
Example: Predict
45:02
Wittig Retrosynthesis
46:19
Wittig Retrosynthesis
46:20
Synthesis
48:09
Reaction with Oxygen Nu:
51:21
Addition of H₂O
51:22
Exception: Formaldehyde is 99% Hydrate in H₂O Solution
54:10
Exception: Hydrate is Favored if Partial Positive Near Carbonyl
55:26
Reaction with Oxygen Nu:
57:45
Addition of ROH
57:46
TsOH: Tosic Acid
58:28
Addition of ROH Cont.
59:09
Example
1:01:43
Predict
1:01:44
Mechanism
1:03:08
Mechanism for Acetal Formation
1:04:10
Mechanism for Acetal Formation
1:04:11
What is a CTI?
1:15:04
Tetrahedral Intermediate
1:15:05
Charged Tetrahedral Intermediate
1:15:45
CTI: Acid-cat
1:16:10
CTI: Base-cat
1:17:01
Acetals & Cyclic Acetals
1:17:49
Overall
1:17:50
Cyclic Acetals
1:18:46
Hydrolysis of Acetals: Regenerates Carbonyl
1:20:01
Hydrolysis of Acetals: Regenerates Carbonyl
1:20:02
Mechanism
1:22:08
Reaction with Nitrogen Nu:
1:30:11
Reaction with Nitrogen Nu:
1:30:12
Example
1:32:18
Mechanism of Imine Formation
1:33:24
Mechanism of Imine Formation
1:33:25
Oxidation of Aldehydes
1:38:12
Oxidation of Aldehydes 1
1:38:13
Oxidation of Aldehydes 2
1:39:52
Oxidation of Aldehydes 3
1:40:10
Reductions of Ketones and Aldehydes
1:40:54
Reductions of Ketones and Aldehydes
1:40:55
Hydride/ Workup
1:41:22
Raney Nickel
1:42:07
Reductions of Ketones and Aldehydes
1:43:24
Clemmensen Reduction & Wolff-Kishner Reduction
1:43:40
Acetals as Protective Groups
1:46:50
Acetals as Protective Groups
1:46:51
Example
1:50:39
Example: Consider the Following Synthesis
1:50:40
Protective Groups
1:54:47
Protective Groups
1:54:48
Example
1:59:02
Example: Transform
1:59:03
Example: Another Route
2:04:54
Example: Transform
2:08:49
Example
2:08:50
Transform
2:08:51
Example
2:11:05
Transform
2:11:06
Example
2:13:45
Transform
2:13:46
Example
2:15:43
Provide the Missing Starting Material
2:15:44
VI. Organic Transformation Practice
Transformation Practice Problems

38m 58s

Intro
0:00
Practice Problems
0:33
Practice Problem 1: Transform
0:34
Practice Problem 2: Transform
3:57
Practice Problems
7:49
Practice Problem 3: Transform
7:50
Practice Problems
15:32
Practice Problem 4: Transform
15:34
Practice Problem 5: Transform
20:15
Practice Problems
24:08
Practice Problem 6: Transform
24:09
Practice Problem 7: Transform
29:27
Practice Problems
33:08
Practice Problem 8: Transform
33:09
Practice Problem 9: Transform
35:23
VII. Carboxylic Acids
Carboxylic Acids

1h 17m 51s

Intro
0:00
Review Reactions of Ketone/Aldehyde
0:06
Carbonyl Reactivity
0:07
Nu: = Hydride (Reduction)
1:37
Nu: = Grignard
2:08
Review Reactions of Ketone/Aldehyde
2:53
Nu: = Alcohol
2:54
Nu: = Amine
3:46
Carboxylic Acids and Their Derivatives
4:37
Carboxylic Acids and Their Derivatives
4:38
Ketone vs. Ester Reactivity
6:33
Ketone Reactivity
6:34
Ester Reactivity
6:55
Carboxylic Acids and Their Derivatives
7:30
Acid Halide, Anhydride, Ester, Amide, and Nitrile
7:43
General Reactions of Acarboxylic Acid Derivatives
9:22
General Reactions of Acarboxylic Acid Derivatives
9:23
Physical Properties of Carboxylic Acids
12:16
Acetic Acid
12:17
Carboxylic Acids
15:46
Aciditiy of Carboxylic Acids, RCO₂H
17:45
Alcohol
17:46
Carboxylic Acid
19:21
Aciditiy of Carboxylic Acids, RCO₂H
21:31
Aciditiy of Carboxylic Acids, RCO₂H
21:32
Aciditiy of Carboxylic Acids, RCO₂H
24:48
Example: Which is the Stronger Acid?
24:49
Aciditiy of Carboxylic Acids, RCO₂H
30:06
Inductive Effects Decrease with Distance
30:07
Preparation of Carboxylic Acids, RCO₂H
31:55
A) By Oxidation
31:56
Preparation of Carboxylic Acids, RCO₂H
34:37
Oxidation of Alkenes/Alkynes - Ozonolysis
34:38
Preparation of Carboxylic Acids, RCO₂H
36:17
B) Preparation of RCO₂H from Organometallic Reagents
36:18
Preparation of Carboxylic Acids, RCO₂H
38:02
Example: Preparation of Carboxylic Acids
38:03
Preparation of Carboxylic Acids, RCO₂H
40:38
C) Preparation of RCO₂H by Hydrolysis of Carboxylic Acid Derivatives
40:39
Hydrolysis Mechanism
42:19
Hydrolysis Mechanism
42:20
Mechanism: Acyl Substitution (Addition/Elimination)
43:05
Hydrolysis Mechanism
47:27
Substitution Reaction
47:28
RO is Bad LG for SN1/SN2
47:39
RO is okay LG for Collapse of CTI
48:31
Hydrolysis Mechanism
50:07
Base-promoted Ester Hydrolysis (Saponification)
50:08
Applications of Carboxylic Acid Derivatives:
53:10
Saponification Reaction
53:11
Ester Hydrolysis
57:15
Acid-Catalyzed Mechanism
57:16
Ester Hydrolysis Requires Acide or Base
1:03:06
Ester Hydrolysis Requires Acide or Base
1:03:07
Nitrile Hydrolysis
1:05:22
Nitrile Hydrolysis
1:05:23
Nitrile Hydrolysis Mechanism
1:06:53
Nitrile Hydrolysis Mechanism
1:06:54
Use of Nitriles in Synthesis
1:12:39
Example: Nitirles in Synthesis
1:12:40
Carboxylic Acid Derivatives

1h 21m 4s

Intro
0:00
Carboxylic Acid Derivatives
0:05
Carboxylic Acid Derivatives
0:06
General Structure
1:00
Preparation of Carboxylic Acid Derivatives
1:19
Which Carbonyl is the Better E+?
1:20
Inductive Effects
1:54
Resonance
3:23
Preparation of Carboxylic Acid Derivatives
6:52
Which is Better E+, Ester or Acid Chloride?
6:53
Inductive Effects
7:02
Resonance
7:20
Preparation of Carboxylic Acid Derivatives
10:45
Which is Better E+, Carboxylic Acid or Anhydride?
10:46
Inductive Effects & Resonance
11:00
Overall: Order of Electrophilicity and Leaving Group
14:49
Order of Electrophilicity and Leaving Group
14:50
Example: Acid Chloride
16:26
Example: Carboxylate
19:17
Carboxylic Acid Derivative Interconversion
20:53
Carboxylic Acid Derivative Interconversion
20:54
Preparation of Acid Halides
24:31
Preparation of Acid Halides
24:32
Preparation of Anhydrides
25:45
A) Dehydration of Acids (For Symmetrical Anhydride)
25:46
Preparation of Anhydrides
27:29
Example: Dehydration of Acids
27:30
Preparation of Anhydrides
29:16
B) From an Acid Chloride (To Make Mixed Anhydride)
29:17
Mechanism
30:03
Preparation of Esters
31:53
A) From Acid Chloride or Anhydride
31:54
Preparation of Esters
33:48
B) From Carboxylic Acids (Fischer Esterification)
33:49
Mechanism
36:55
Preparations of Esters
41:38
Example: Predict the Product
41:39
Preparation of Esters
43:17
C) Transesterification
43:18
Mechanism
45:17
Preparation of Esters
47:58
D) SN2 with Carboxylate
47:59
Mechanism: Diazomethane
49:28
Preparation of Esters
51:01
Example: Transform
51:02
Preparation of Amides
52:27
A) From an Acid Cl or Anhydride
52:28
Preparations of Amides
54:47
B) Partial Hydrolysis of Nitriles
54:48
Preparation of Amides
56:11
Preparation of Amides: Find Alternate Path
56:12
Preparation of Amides
59:04
C) Can't be Easily Prepared from RCO₂H Directly
59:05
Reactions of Carboxylic Acid Derivatives with Nucleophiles
1:01:41
A) Hydride Nu: Review
1:01:42
A) Hydride Nu: Sodium Borohydride + Ester
1:02:43
Reactions of Carboxylic Acid Derivatives with Nucleophiles
1:03:57
Lithium Aluminum Hydride (LAH)
1:03:58
Mechanism
1:04:29
Summary of Hydride Reductions
1:07:09
Summary of Hydride Reductions 1
1:07:10
Summary of Hydride Reductions 2
1:07:36
Hydride Reduction of Amides
1:08:12
Hydride Reduction of Amides Mechanism
1:08:13
Reaction of Carboxylic Acid Derivatives with Organometallics
1:12:04
Review 1
1:12:05
Review 2
1:12:50
Reaction of Carboxylic Acid Derivatives with Organometallics
1:14:22
Example: Lactone
1:14:23
Special Hydride Nu: Reagents
1:16:34
Diisobutylaluminum Hydride
1:16:35
Example
1:17:25
Other Special Hydride
1:18:41
Addition of Organocuprates to Acid Chlorides
1:19:07
Addition of Organocuprates to Acid Chlorides
1:19:08
VIII. Enols & Enolates
Enols and Enolates, Part 1

1h 26m 22s

Intro
0:00
Enols and Enolates
0:09
The Carbonyl
0:10
Keto-Enol Tautomerization
1:17
Keto-Enol Tautomerization Mechanism
2:28
Tautomerization Mechanism (2 Steps)
2:29
Keto-Enol Tautomerization Mechanism
5:15
Reverse Reaction
5:16
Mechanism
6:07
Formation of Enolates
7:27
Why is a Ketone's α H's Acidic?
7:28
Formation of Other Carbanions
10:05
Alkyne
10:06
Alkane and Alkene
10:53
Formation of an Enolate: Choice of Base
11:27
Example: Choice of Base
11:28
Formation of an Enolate: Choice of Base
13:56
Deprotonate, Stronger Base, and Lithium Diisopropyl Amide (LDA)
13:57
Formation of an Enolate: Choice of Base
15:48
Weaker Base & 'Active' Methylenes
15:49
Why Use NaOEt instead of NaOH?
19:01
Other Acidic 'α' Protons
20:30
Other Acidic 'α' Protons
20:31
Why is an Ester Less Acidic than a Ketone?
24:10
Other Acidic 'α' Protons
25:19
Other Acidic 'α' Protons Continue
25:20
How are Enolates Used
25:54
Enolates
25:55
Possible Electrophiles
26:21
Alkylation of Enolates
27:56
Alkylation of Enolates
27:57
Resonance Form
30:03
α-Halogenation
32:17
α-Halogenation
32:18
Iodoform Test for Methyl Ketones
33:47
α-Halogenation
35:55
Acid-Catalyzed
35:57
Mechanism: 1st Make Enol (2 Steps)
36:14
Whate Other Eloctrophiles ?
39:17
Aldol Condensation
39:38
Aldol Condensation
39:39
Aldol Mechanism
41:26
Aldol Mechanism: In Base, Deprotonate First
41:27
Aldol Mechanism
45:28
Mechanism for Loss of H₂O
45:29
Collapse of CTI and β-elimination Mechanism
47:51
Loss of H₂0 is not E2!
48:39
Aldol Summary
49:53
Aldol Summary
49:54
Base-Catalyzed Mechanism
52:34
Acid-Catalyzed Mechansim
53:01
Acid-Catalyzed Aldol Mechanism
54:01
First Step: Make Enol
54:02
Acid-Catalyzed Aldol Mechanism
56:54
Loss of H₂0 (β elimination)
56:55
Crossed/Mixed Aldol
1:00:55
Crossed/Mixed Aldol & Compound with α H's
1:00:56
Ketone vs. Aldehyde
1:02:30
Crossed/Mixed Aldol & Compound with α H's Continue
1:03:10
Crossed/Mixed Aldol
1:05:21
Mixed Aldol: control Using LDA
1:05:22
Crossed/Mixed Aldol Retrosynthesis
1:08:53
Example: Predic Aldol Starting Material (Aldol Retrosyntheiss)
1:08:54
Claisen Condensation
1:12:54
Claisen Condensation (Aldol on Esters)
1:12:55
Claisen Condensation
1:19:52
Example 1: Claisen Condensation
1:19:53
Claisen Condensation
1:22:48
Example 2: Claisen Condensation
1:22:49
Enols and Enolates, Part 2

50m 57s

Intro
0:00
Conjugate Additions
0:06
α, β-unsaturated Carbonyls
0:07
Conjugate Additions
1:50
'1,2-addition'
1:51
'1,-4-addition' or 'Conjugate Addition'
2:24
Conjugate Additions
4:53
Why can a Nu: Add to this Alkene?
4:54
Typical Alkene
5:09
α, β-unsaturated Alkene
5:39
Electrophilic Alkenes: Michael Acceptors
6:35
Other 'Electrophilic' Alkenes (Called 'Michael Acceptors)
6:36
1,4-Addition of Cuprates (R2CuLi)
8:29
1,4-Addition of Cuprates (R2CuLi)
8:30
1,4-Addition of Cuprates (R2CuLi)
11:23
Use Cuprates in Synthesis
11:24
Preparation of Cuprates
12:25
Prepare Organocuprate From Organolithium
12:26
Cuprates Also Do SN2 with RX E+ (Not True for RMgX, RLi)
13:06
1,4-Addition of Enolates: Michael Reaction
13:50
1,4-Addition of Enolates: Michael Reaction
13:51
Mechanism
15:57
1,4-Addition of Enolates: Michael Reaction
18:47
Example: 1,4-Addition of Enolates
18:48
1,4-Addition of Enolates: Michael Reaction
21:02
Michael Reaction, Followed by Intramolecular Aldol
21:03
Mechanism of the Robinson Annulation
24:26
Mechanism of the Robinson Annulation
24:27
Enols and Enolates: Advanced Synthesis Topics
31:10
Stablized Enolates and the Decarboxylation Reaction
31:11
Mechanism: A Pericyclic Reaction
32:08
Enols and Enolates: Advanced Synthesis Topics
33:32
Example: Advance Synthesis
33:33
Enols and Enolates: Advanced Synthesis Topics
36:10
Common Reagents: Diethyl Malonate
36:11
Common Reagents: Ethyl Acetoacetate
37:27
Enols and Enolates: Advanced Synthesis Topics
38:06
Example: Transform
38:07
Advanced Synthesis Topics: Enamines
41:52
Enamines
41:53
Advanced Synthesis Topics: Enamines
43:06
Reaction with Ketone/Aldehyde
43:07
Example
44:08
Advanced Synthesis Topics: Enamines
45:31
Example: Use Enamines as Nu: (Like Enolate)
45:32
Advanced Synthesis Topics: Enamines
47:56
Example
47:58
IX. Aromatic Compounds
Aromatic Compounds: Structure

1h 59s

Intro
0:00
Aromatic Compounds
0:05
Benzene
0:06
3D Sketch
1:33
Features of Benzene
4:41
Features of Benzene
4:42
Aromatic Stability
6:41
Resonance Stabilization of Benzene
6:42
Cyclohexatriene
7:24
Benzene (Actual, Experimental)
8:11
Aromatic Stability
9:03
Energy Graph
9:04
Aromaticity Requirements
9:55
1) Cyclic and Planar
9:56
2) Contiguous p Orbitals
10:49
3) Satisfy Huckel's Rule
11:20
Example: Benzene
12:32
Common Aromatic Compounds
13:28
Example: Pyridine
13:29
Common Aromatic Compounds
16:25
Example: Furan
16:26
Common Aromatic Compounds
19:42
Example: Thiophene
19:43
Example: Pyrrole
20:18
Common Aromatic Compounds
21:09
Cyclopentadienyl Anion
21:10
Cycloheptatrienyl Cation
23:48
Naphthalene
26:04
Determining Aromaticity
27:28
Example: Which of the Following are Aromatic?
27:29
Molecular Orbital (MO) Theory
32:26
What's So Special About '4n + 2' Electrons?
32:27
π bond & Overlapping p Orbitals
32:53
Molecular Orbital (MO) Diagrams
36:56
MO Diagram: Benzene
36:58
Drawing MO Diagrams
44:26
Example: 3-Membered Ring
44:27
Example: 4-Membered Ring
46:04
Drawing MO Diagrams
47:51
Example: 5-Membered Ring
47:52
Example: 8-Membered Ring
49:32
Aromaticity and Reactivity
51:03
Example: Which is More Acidic?
51:04
Aromaticity and Reactivity
56:03
Example: Which has More Basic Nitrogen, Pyrrole or Pyridine?
56:04
Aromatic Compounds: Reactions, Part 1

1h 24m 4s

Intro
0:00
Reactions of Benzene
0:07
N/R as Alkenes
0:08
Substitution Reactions
0:50
Electrophilic Aromatic Substitution
1:24
Electrophilic Aromatic Substitution
1:25
Mechanism Step 1: Addition of Electrophile
2:08
Mechanism Step 2: Loss of H+
4:14
Electrophilic Aromatic Substitution on Substituted Benzenes
5:21
Electron Donating Group
5:22
Electron Withdrawing Group
8:02
Halogen
9:23
Effects of Electron-Donating Groups (EDG)
10:23
Effects of Electron-Donating Groups (EDG)
10:24
What Effect Does EDG (OH) Have?
11:40
Reactivity
13:03
Regioselectivity
14:07
Regioselectivity: EDG is o/p Director
14:57
Prove It! Add E+ and Look at Possible Intermediates
14:58
Is OH Good or Bad?
17:38
Effects of Electron-Withdrawing Groups (EWG)
20:20
What Effect Does EWG Have?
20:21
Reactivity
21:28
Regioselectivity
22:24
Regioselectivity: EWG is a Meta Director
23:23
Prove It! Add E+ and Look at Competing Intermediates
23:24
Carbocation: Good or Bad?
26:01
Effects of Halogens on EAS
28:33
Inductive Withdrawal of e- Density vs. Resonance Donation
28:34
Summary of Substituent Effects on EAS
32:33
Electron Donating Group
32:34
Electron Withdrawing Group
33:37
Directing Power of Substituents
34:35
Directing Power of Substituents
34:36
Example
36:41
Electrophiles for Electrophilic Aromatic Substitution
38:43
Reaction: Halogenation
38:44
Electrophiles for Electrophilic Aromatic Substitution
40:27
Reaction: Nitration
40:28
Electrophiles for Electrophilic Aromatic Substitution
41:45
Reaction: Sulfonation
41:46
Electrophiles for Electrophilic Aromatic Substitution
43:19
Reaction: Friedel-Crafts Alkylation
43:20
Electrophiles for Electrophilic Aromatic Substitution
45:43
Reaction: Friedel-Crafts Acylation
45:44
Electrophilic Aromatic Substitution: Nitration
46:52
Electrophilic Aromatic Substitution: Nitration
46:53
Mechanism
48:56
Nitration of Aniline
52:40
Nitration of Aniline Part 1
52:41
Nitration of Aniline Part 2: Why?
54:12
Nitration of Aniline
56:10
Workaround: Protect Amino Group as an Amide
56:11
Electrophilic Aromatic Substitution: Sulfonation
58:16
Electrophilic Aromatic Substitution: Sulfonation
58:17
Example: Transform
59:25
Electrophilic Aromatic Substitution: Friedel-Crafts Alkylation
1:02:24
Electrophilic Aromatic Substitution: Friedel-Crafts Alkylation
1:02:25
Example & Mechanism
1:03:37
Friedel-Crafts Alkylation Drawbacks
1:05:48
A) Can Over-React (Dialkylation)
1:05:49
Friedel-Crafts Alkylation Drawbacks
1:08:21
B) Carbocation Can Rearrange
1:08:22
Mechanism
1:09:33
Friedel-Crafts Alkylation Drawbacks
1:13:35
Want n-Propyl? Use Friedel-Crafts Acylation
1:13:36
Reducing Agents
1:16:45
Synthesis with Electrophilic Aromatic Substitution
1:18:45
Example: Transform
1:18:46
Synthesis with Electrophilic Aromatic Substitution
1:20:59
Example: Transform
1:21:00
Aromatic Compounds: Reactions, Part 2

59m 10s

Intro
0:00
Reagents for Electrophilic Aromatic Substitution
0:07
Reagents for Electrophilic Aromatic Substitution
0:08
Preparation of Diazonium Salt
2:12
Preparation of Diazonium Salt
2:13
Reagents for Sandmeyer Reactions
4:14
Reagents for Sandmeyer Reactions
4:15
Apply Diazonium Salt in Synthesis
6:20
Example: Transform
6:21
Apply Diazonium Salt in Synthesis
9:14
Example: Synthesize Following Target Molecule from Benzene or Toluene
9:15
Apply Diazonium Salt in Synthesis
14:56
Example: Transform
14:57
Reactions of Aromatic Substituents
21:56
A) Reduction Reactions
21:57
Reactions of Aromatic Substituents
23:24
B) Oxidations of Arenes
23:25
Benzylic [ox] Even Breaks C-C Bonds!
25:05
Benzylic Carbon Can't Be Quaternary
25:55
Reactions of Aromatic Substituents
26:21
Example
26:22
Review of Benzoic Acid Synthesis
27:34
Via Hydrolysis
27:35
Via Grignard
28:20
Reactions of Aromatic Substituents
29:15
C) Benzylic Halogenation
29:16
Radical Stabilities
31:55
N-bromosuccinimide (NBS)
32:23
Reactions of Aromatic Substituents
33:08
D) Benzylic Substitutions
33:09
Reactions of Aromatic Side Chains
37:08
Example: Transform
37:09
Nucleophilic Aromatic Substitution
43:13
Nucleophilic Aromatic Substitution
43:14
Nucleophilic Aromatic Substitution
47:08
Example
47:09
Mechanism
48:00
Nucleophilic Aromatic Substitution
50:43
Example
50:44
Nucleophilic Substitution: Benzyne Mechanism
52:46
Nucleophilic Substitution: Benzyne Mechanism
52:47
Nucleophilic Substitution: Benzyne Mechanism
57:31
Example: Predict Product
57:32
X. Dienes & Amines
Conjugated Dienes

1h 9m 12s

Intro
0:00
Conjugated Dienes
0:08
Conjugated π Bonds
0:09
Diene Stability
2:00
Diene Stability: Cumulated
2:01
Diene Stability: Isolated
2:37
Diene Stability: Conjugated
2:51
Heat of Hydrogenation
3:00
Allylic Carbocations and Radicals
5:15
Allylic Carbocations and Radicals
5:16
Electrophilic Additions to Dienes
7:00
Alkenes
7:01
Unsaturated Ketone
7:47
Electrophilic Additions to Dienes
8:28
Conjugated Dienes
8:29
Electrophilic Additions to Dienes
9:46
Mechanism (2-Steps): Alkene
9:47
Electrophilic Additions to Dienes
11:40
Mechanism (2-Steps): Diene
11:41
1,2 'Kinetic' Product
13:08
1,4 'Thermodynamic' Product
14:47
E vs. POR Diagram
15:50
E vs. POR Diagram
15:51
Kinetic vs. Thermodynamic Control
21:56
Kinetic vs. Thermodynamic Control
21:57
How? Reaction is Reversible!
23:51
1,2 (Less Stable product)
23:52
1,4 (More Stable Product)
25:16
Diels Alder Reaction
26:34
Diels Alder Reaction
26:35
Dienophiles (E+)
29:23
Dienophiles (E+)
29:24
Alkyne Diels-Alder Example
30:48
Example: Alkyne Diels-Alder
30:49
Diels-Alder Reaction: Dienes (Nu:)
32:22
Diels-Alder ReactionL Dienes (Nu:)
32:23
Diels-Alder Reaction: Dienes
33:51
Dienes Must Have 's-cis' Conformation
33:52
Example
35:25
Diels-Alder Reaction with Cyclic Dienes
36:08
Cyclic Dienes are Great for Diels-Alder Reaction
36:09
Cyclopentadiene
37:10
Diels-Alder Reaction: Bicyclic Products
40:50
Endo vs. Exo Terminology: Norbornane & Bicyclo Heptane
40:51
Example: Bicyclo Heptane
42:29
Diels-Alder Reaction with Cyclic Dienes
44:15
Example
44:16
Stereochemistry of the Diels-Alder Reaction
47:39
Stereochemistry of the Diels-Alder Reaction
47:40
Example
48:08
Stereochemistry of the Diels-Alder Reaction
50:21
Example
50:22
Regiochemistry of the Diels-Alder Reaction
52:42
Rule: 1,2-Product Preferred Over 1,3-Product
52:43
Regiochemistry of the Diels-Alder Reaction
54:18
Rule: 1,4-Product Preferred Over 1,3-Product
54:19
Regiochemistry of the Diels-Alder Reaction
55:02
Why 1,2-Product or 1,4-Product Favored?
55:03
Example
56:11
Diels-Alder Reaction
58:06
Example: Predict
58:07
Diels-Alder Reaction
1:01:27
Explain Why No Diels-Alder Reaction Takes Place in This Case
1:01:28
Diels-Alder Reaction
1:03:09
Example: Predict
1:03:10
Diels-Alder Reaction: Synthesis Problem
1:05:39
Diels-Alder Reaction: Synthesis Problem
1:05:40
Pericyclic Reactions and Molecular Orbital (MO) Theory

1h 21m 31s

Intro
0:00
Pericyclic Reactions
0:05
Pericyclic Reactions
0:06
Electrocyclic Reactions
1:19
Electrocyclic Reactions
1:20
Electrocyclic Reactions
3:13
Stereoselectivity
3:14
Electrocyclic Reactions
8:10
Example: Predict
8:11
Sigmatropic Rearrangements
12:29
Sigmatropic Rearrangements
12:30
Cope Rearrangement
14:44
Sigmatropic Rearrangements
16:44
Claisen Rearrangement 1
16:45
Claisen Rearrangement 2
17:46
Cycloaddition Reactions
19:22
Diels-Alder
19:23
1,3-Dipolar Cycloaddition
20:32
Cycloaddition Reactions: Stereochemistry
21:58
Cycloaddition Reactions: Stereochemistry
21:59
Cycloaddition Reactions: Heat or Light?
26:00
4+2 Cycloadditions
26:01
2+2 Cycloadditions
27:23
Molecular Orbital (MO) Theory of Chemical Reactions
29:26
Example 1: Molecular Orbital Theory of Bonding
29:27
Molecular Orbital (MO) Theory of Chemical Reactions
31:59
Example 2: Molecular Orbital Theory of Bonding
32:00
Molecular Orbital (MO) Theory of Chemical Reactions
33:33
MO Theory of Aromaticity, Huckel's Rule
33:34
Molecular Orbital (MO) Theory of Chemical Reactions
36:43
Review: Molecular Orbital Theory of Conjugated Systems
36:44
Molecular Orbital (MO) Theory of Chemical Reactions
44:56
Review: Molecular Orbital Theory of Conjugated Systems
44:57
Molecular Orbital (MO) Theory of Chemical Reactions
46:54
Review: Molecular Orbital Theory of Conjugated Systems
46:55
Molecular Orbital (MO) Theory of Chemical Reactions
48:36
Frontier Molecular Orbitals are Involved in Reactions
48:37
Examples
50:20
MO Theory of Pericyclic Reactions: The Woodward-Hoffmann Rules
51:51
Heat-promoted Pericyclic Reactions and Light-promoted Pericyclic Reactions
51:52
MO Theory of Pericyclic Reactions: The Woodward-Hoffmann Rules
53:42
Why is a [4+2] Cycloaddition Thermally Allowed While the [2+2] is Not?
53:43
MO Theory of Pericyclic Reactions: The Woodward-Hoffmann Rules
56:51
Why is a [2+2] Cycloaddition Photochemically Allowed?
56:52
Pericyclic Reaction Example I
59:16
Pericyclic Reaction Example I
59:17
Pericyclic Reaction Example II
1:07:40
Pericyclic Reaction Example II
1:07:41
Pericyclic Reaction Example III: Vitamin D - The Sunshine Vitamin
1:14:22
Pericyclic Reaction Example III: Vitamin D - The Sunshine Vitamin
1:14:23
Amines

34m 58s

Intro
0:00
Amines: Properties and Reactivity
0:04
Compare Amines to Alcohols
0:05
Amines: Lower Boiling Point than ROH
0:55
1) RNH₂ Has Lower Boiling Point than ROH
0:56
Amines: Better Nu: Than ROH
2:22
2) RNH₂ is a Better Nucleophile than ROH Example 1
2:23
RNH₂ is a Better Nucleophile than ROH Example 2
3:08
Amines: Better Nu: than ROH
3:47
Example
3:48
Amines are Good Bases
5:41
3) RNH₂ is a Good Base
5:42
Amines are Good Bases
7:06
Example 1
7:07
Example 2: Amino Acid
8:27
Alkyl vs. Aryl Amines
9:56
Example: Which is Strongest Base?
9:57
Alkyl vs. Aryl Amines
14:55
Verify by Comparing Conjugate Acids
14:56
Reaction of Amines
17:42
Reaction with Ketone/Aldehyde: 1° Amine (RNH₂)
17:43
Reaction of Amines
18:48
Reaction with Ketone/Aldehyde: 2° Amine (R2NH)
18:49
Use of Enamine: Synthetic Equivalent of Enolate
20:08
Use of Enamine: Synthetic Equivalent of Enolate
20:09
Reaction of Amines
24:10
Hofmann Elimination
24:11
Hofmann Elimination
26:16
Kinetic Product
26:17
Structure Analysis Using Hofmann Elimination
28:22
Structure Analysis Using Hofmann Elimination
28:23
Biological Activity of Amines
30:30
Adrenaline
31:07
Mescaline (Peyote Alkaloid)
31:22
Amino Acids, Amide, and Protein
32:14
Biological Activity of Amines
32:50
Morphine (Opium Alkaloid)
32:51
Epibatidine (Poison Dart Frog)
33:28
Nicotine
33:48
Choline (Nerve Impulse)
34:03
XI. Biomolecules & Polymers
Biomolecules

1h 53m 20s

Intro
0:00
Carbohydrates
1:11
D-glucose Overview
1:12
D-glucose: Cyclic Form (6-membered ring)
4:31
Cyclic Forms of Glucose: 6-membered Ring
8:24
α-D-glucopyranose & β-D-glucopyranose
8:25
Formation of a 5-Membered Ring
11:05
D-glucose: Formation of a 5-Membered Ring
11:06
Cyclic Forms of Glucose: 5-membered Ring
12:37
α-D-glucofuranose & β-D-glucofuranose
12:38
Carbohydrate Mechanism
14:03
Carbohydrate Mechanism
14:04
Reactions of Glucose: Acetal Formation
21:35
Acetal Formation: Methyl-α-D-glucoside
21:36
Hemiacetal to Acetal: Overview
24:58
Mechanism for Formation of Glycosidic Bond
25:51
Hemiacetal to Acetal: Mechanism
25:52
Formation of Disaccharides
29:34
Formation of Disaccharides
29:35
Some Polysaccharides: Starch
31:33
Amylose & Amylopectin
31:34
Starch: α-1,4-glycosidic Bonds
32:22
Properties of Starch Molecule
33:21
Some Polysaccharides: Cellulose
33:59
Cellulose: β-1,4-glycosidic bonds
34:00
Properties of Cellulose
34:59
Other Sugar-Containing Biomolecules
35:50
Ribonucleoside (RNA)
35:51
Deoxyribonucleoside (DMA)
36:59
Amino Acids & Proteins
37:32
α-amino Acids: Structure & Stereochemistry
37:33
Making a Protein (Condensation)
42:46
Making a Protein (Condensation)
42:47
Peptide Bond is Planar (Amide Resonance)
44:55
Peptide Bond is Planar (Amide Resonance)
44:56
Protein Functions
47:49
Muscle, Skin, Bones, Hair Nails
47:50
Enzymes
49:10
Antibodies
49:44
Hormones, Hemoglobin
49:58
Gene Regulation
50:20
Various Amino Acid Side Chains
50:51
Nonpolar
50:52
Polar
51:15
Acidic
51:24
Basic
51:55
Amino Acid Table
52:22
Amino Acid Table
52:23
Isoelectric Point (pI)
53:43
Isoelectric Point (pI) of Glycine
53:44
Isoelectric Point (pI) of Glycine: pH 11
56:42
Isoelectric Point (pI) of Glycine: pH 1
57:20
Isoelectric Point (pI), cont.
58:05
Asparatic Acid
58:06
Histidine
1:00:28
Isoelectric Point (pI), cont.
1:02:54
Example: What is the Net Charge of This Tetrapeptide at pH 6.0?
1:02:55
Nucleic Acids: Ribonucleosides
1:10:32
Nucleic Acids: Ribonucleosides
1:10:33
Nucleic Acids: Ribonucleotides
1:11:48
Ribonucleotides: 5' Phosphorylated Ribonucleosides
1:11:49
Ribonucleic Acid (RNA) Structure
1:12:35
Ribonucleic Acid (RNA) Structure
1:12:36
Nucleic Acids: Deoxyribonucleosides
1:14:08
Nucleic Acids: Deoxyribonucleosides
1:14:09
Deoxythymidine (T)
1:14:36
Nucleic Acids: Base-Pairing
1:15:17
Nucleic Acids: Base-Pairing
1:15:18
Double-Stranded Structure of DNA
1:18:16
Double-Stranded Structure of DNA
1:18:17
Model of DNA
1:19:40
Model of DNA
1:19:41
Space-Filling Model of DNA
1:20:46
Space-Filling Model of DNA
1:20:47
Function of RNA and DNA
1:23:06
DNA & Transcription
1:23:07
RNA & Translation
1:24:22
Genetic Code
1:25:09
Genetic Code
1:25:10
Lipids/Fats/Triglycerides
1:27:10
Structure of Glycerol
1:27:43
Saturated & Unsaturated Fatty Acids
1:27:51
Triglyceride
1:28:43
Unsaturated Fats: Lower Melting Points (Liquids/Oils)
1:29:15
Saturated Fat
1:29:16
Unsaturated Fat
1:30:10
Partial Hydrogenation
1:32:05
Saponification of Fats
1:35:11
Saponification of Fats
1:35:12
History of Soap
1:36:50
Carboxylate Salts form Micelles in Water
1:41:02
Carboxylate Salts form Micelles in Water
1:41:03
Cleaning Power of Micelles
1:42:21
Cleaning Power of Micelles
1:42:22
3-D Image of a Micelle
1:42:58
3-D Image of a Micelle
1:42:59
Synthesis of Biodiesel
1:44:04
Synthesis of Biodiesel
1:44:05
Phosphoglycerides
1:47:54
Phosphoglycerides
1:47:55
Cell Membranes Contain Lipid Bilayers
1:48:41
Cell Membranes Contain Lipid Bilayers
1:48:42
Bilayer Acts as Barrier to Movement In/Out of Cell
1:50:24
Bilayer Acts as Barrier to Movement In/Out of Cell
1:50:25
Organic Chemistry Meets Biology… Biochemistry!
1:51:12
Organic Chemistry Meets Biology… Biochemistry!
1:51:13
Polymers

45m 47s

Intro
0:00
Polymers
0:05
Monomer to Polymer: Vinyl Chloride to Polyvinyl Chloride
0:06
Polymer Properties
1:32
Polymer Properties
1:33
Natural Polymers: Rubber
2:30
Vulcanization
2:31
Natural Polymers: Polysaccharides
4:55
Example: Starch
4:56
Example: Cellulose
5:45
Natural Polymers: Proteins
6:07
Example: Keratin
6:08
DNA Strands
7:15
DNA Strands
7:16
Synthetic Polymers
8:30
Ethylene & Polyethylene: Lightweight Insulator & Airtight Plastic
8:31
Synthetic Organic Polymers
12:22
Polyethylene
12:28
Polyvinyl Chloride (PVC)
12:54
Polystyrene
13:28
Polyamide
14:34
Polymethyl Methacrylate
14:57
Kevlar
15:25
Synthetic Material Examples
16:30
How are Polymers Made?
21:00
Chain-growth Polymers Additions to Alkenes can be Radical, Cationic or Anionic
21:01
Chain Branching
22:34
Chain Branching
22:35
Special Reaction Conditions Prevent Branching
24:28
Ziegler-Natta Catalyst
24:29
Chain-Growth by Cationic Polymerization
27:35
Chain-Growth by Cationic Polymerization
27:36
Chain-Growth by Anionic Polymerization
29:35
Chain-Growth by Anionic Polymerization
29:36
Step-Growth Polymerization: Polyamides
32:16
Step-Growth Polymerization: Polyamides
32:17
Step-Growth Polymerization: Polyesters
34:23
Step-Growth Polymerization: Polyesters
34:24
Step-Growth Polymerization: Polycarbonates
35:56
Step-Growth Polymerization: Polycarbonates
35:57
Step-Growth Polymerization: Polyurethanes
37:18
Step-Growth Polymerization: Polyurethanes
37:19
Modifying Polymer Properties
39:35
Glass Transition Temperature
40:04
Crosslinking
40:42
Copolymers
40:58
Additives: Stabilizers
42:08
Additives: Flame Retardants
43:03
Additives: Plasticizers
43:41
Additives: Colorants
44:54
XII. Organic Synthesis
Organic Synthesis Strategies

2h 20m 24s

Intro
0:00
Organic Synthesis Strategies
0:15
Goal
0:16
Strategy
0:29
Example of a RetroSynthesis
1:30
Finding Starting Materials for Target Molecule
1:31
Synthesis Using Starting Materials
4:56
Synthesis of Alcohols by Functional Group Interconversion (FGI)
6:00
Synthesis of Alcohols by Functional Group Interconversion Overview
6:01
Alcohols by Reduction
7:43
Ketone to Alcohols
7:45
Aldehyde to Alcohols
8:26
Carboxylic Acid Derivative to Alcohols
8:36
Alcohols by Hydration of Alkenes
9:28
Hydration of Alkenes Using H₃O⁺
9:29
Oxymercuration-Demercuration
10:35
Hydroboration Oxidation
11:02
Alcohols by Substitution
11:42
Primary Alkyl Halide to Alcohols Using NaOH
11:43
Secondary Alkyl Halide to Alcohols Using Sodium Acetate
13:07
Tertiary Alkyl Halide to Alcohols Using H₂O
15:08
Synthesis of Alcohols by Forming a New C-C Bond
15:47
Recall: Alcohol & RMgBr
15:48
Retrosynthesis
17:28
Other Alcohol Disconnections
19:46
19:47
Synthesis Using PhMGgBr: Example 2
23:05
Synthesis of Alkyl Halides
26:06
Synthesis of Alkyl Halides Overview
26:07
Synthesis of Alkyl Halides by Free Radical Halogenation
27:04
Synthesis of Alkyl Halides by Free Radical Halogenation
27:05
Synthesis of Alkyl Halides by Substitution
29:06
Alcohol to Alkyl Halides Using HBr or HCl
29:07
Alcohol to Alkyl Halides Using SOCl₂
30:57
Alcohol to Alkyl Halides Using PBr₃ and Using P, I₂
31:03
Synthesis of Alkyl Halides by Addition
32:02
Alkene to Alkyl Halides Using HBr
32:03
Alkene to Alkyl Halides Using HBr & ROOR (Peroxides)
32:35
Example: Synthesis of Alkyl Halide
34:18
Example: Synthesis of Alkyl Halide
34:19
Synthesis of Ethers
39:25
Synthesis of Ethers
39:26
Example: Synthesis of an Ether
41:12
Synthesize TBME (t-butyl methyl ether) from Alcohol Starting Materials
41:13
Synthesis of Amines
46:05
Synthesis of Amines
46:06
Gabriel Synthesis of Amines
47:57
Gabriel Synthesis of Amines
47:58
Amines by SN2 with Azide Nu:
49:50
Amines by SN2 with Azide Nu:
49:51
Amines by SN2 with Cyanide Nu:
50:31
Amines by SN2 with Cyanide Nu:
50:32
Amines by Reduction of Amides
51:30
Amines by Reduction of Amides
51:31
Reductive Amination of Ketones/Aldehydes
52:42
Reductive Amination of Ketones/Aldehydes
52:43
Example : Synthesis of an Amine
53:47
Example 1: Synthesis of an Amine
53:48
Example 2: Synthesis of an Amine
56:16
Synthesis of Alkenes
58:20
Synthesis of Alkenes Overview
58:21
Synthesis of Alkenes by Elimination
59:04
Synthesis of Alkenes by Elimination Using NaOH & Heat
59:05
Synthesis of Alkenes by Elimination Using H₂SO₄ & Heat
59:57
Synthesis of Alkenes by Reduction
1:02:05
Alkyne to Cis Alkene
1:02:06
Alkyne to Trans Alkene
1:02:56
Synthesis of Alkenes by Wittig Reaction
1:03:46
Synthesis of Alkenes by Wittig Reaction
1:03:47
Retrosynthesis of an Alkene
1:05:35
Example: Synthesis of an Alkene
1:06:57
Example: Synthesis of an Alkene
1:06:58
Making a Wittig Reagent
1:10:31
Synthesis of Alkynes
1:13:09
Synthesis of Alkynes
1:13:10
Synthesis of Alkynes by Elimination (FGI)
1:13:42
First Step: Bromination of Alkene
1:13:43
Second Step: KOH Heat
1:14:22
Synthesis of Alkynes by Alkylation
1:15:02
Synthesis of Alkynes by Alkylation
1:15:03
Retrosynthesis of an Alkyne
1:16:18
Example: Synthesis of an Alkyne
1:17:40
Example: Synthesis of an Alkyne
1:17:41
Synthesis of Alkanes
1:20:52
Synthesis of Alkanes
1:20:53
Synthesis of Aldehydes & Ketones
1:21:38
Oxidation of Alcohol Using PCC or Swern
1:21:39
Oxidation of Alkene Using 1) O₃, 2)Zn
1:22:42
Reduction of Acid Chloride & Nitrile Using DiBAL-H
1:23:25
Hydration of Alkynes
1:24:55
Synthesis of Ketones by Acyl Substitution
1:26:12
Reaction with R'₂CuLi
1:26:13
Reaction with R'MgBr
1:27:13
Synthesis of Aldehydes & Ketones by α-Alkylation
1:28:00
Synthesis of Aldehydes & Ketones by α-Alkylation
1:28:01
Retrosynthesis of a Ketone
1:30:10
Acetoacetate Ester Synthesis of Ketones
1:31:05
Acetoacetate Ester Synthesis of Ketones: Step 1
1:31:06
Acetoacetate Ester Synthesis of Ketones: Step 2
1:32:13
Acetoacetate Ester Synthesis of Ketones: Step 3
1:32:50
Example: Synthesis of a Ketone
1:34:11
Example: Synthesis of a Ketone
1:34:12
Synthesis of Carboxylic Acids
1:37:15
Synthesis of Carboxylic Acids
1:37:16
Example: Synthesis of a Carboxylic Acid
1:37:59
Example: Synthesis of a Carboxylic Acid (Option 1)
1:38:00
Example: Synthesis of a Carboxylic Acid (Option 2)
1:40:51
Malonic Ester Synthesis of Carboxylic Acid
1:42:34
Malonic Ester Synthesis of Carboxylic Acid: Step 1
1:42:35
Malonic Ester Synthesis of Carboxylic Acid: Step 2
1:43:36
Malonic Ester Synthesis of Carboxylic Acid: Step 3
1:44:01
Example: Synthesis of a Carboxylic Acid
1:44:53
Example: Synthesis of a Carboxylic Acid
1:44:54
Synthesis of Carboxylic Acid Derivatives
1:48:05
Synthesis of Carboxylic Acid Derivatives
1:48:06
Alternate Ester Synthesis
1:48:58
Using Fischer Esterification
1:48:59
Using SN2 Reaction
1:50:18
Using Diazomethane
1:50:56
Using 1) LDA, 2) R'-X
1:52:15
Practice: Synthesis of an Alkyl Chloride
1:53:11
Practice: Synthesis of an Alkyl Chloride
1:53:12
Patterns of Functional Groups in Target Molecules
1:59:53
Recall: Aldol Reaction
1:59:54
β-hydroxy Ketone Target Molecule
2:01:12
α,β-unsaturated Ketone Target Molecule
2:02:20
Patterns of Functional Groups in Target Molecules
2:03:15
Recall: Michael Reaction
2:03:16
Retrosynthesis: 1,5-dicarbonyl Target Molecule
2:04:07
Patterns of Functional Groups in Target Molecules
2:06:38
Recall: Claisen Condensation
2:06:39
Retrosynthesis: β-ketoester Target Molecule
2:07:30
2-Group Target Molecule Summary
2:09:03
2-Group Target Molecule Summary
2:09:04
Example: Synthesis of Epoxy Ketone
2:11:19
Synthesize the Following Target Molecule from Cyclohexanone: Part 1 - Retrosynthesis
2:11:20
Synthesize the Following Target Molecule from Cyclohexanone: Part 2 - Synthesis
2:14:10
Example: Synthesis of a Diketone
2:16:57
Synthesis of a Diketone: Step 1 - Retrosynthesis
2:16:58
Synthesis of a Diketone: Step 2 - Synthesis
2:18:51
XII. Organic Synthesis & Organic Analysis
Organic Analysis: Classical & Modern Methods

46m 46s

Intro
0:00
Organic Analysis: Classical Methods
0:17
Classical Methods for Identifying Chemicals
0:18
Organic Analysis: Classical Methods
2:21
When is Structure Identification Needed?
2:22
Organic Analysis: Classical Methods
6:17
Classical Methods of Structure Identification: Physical Appearance
6:18
Classical Methods of Structure Identification: Physical Constants
6:42
Organic Analysis: Classical Methods
7:37
Classical Methods of Structure Identification: Solubility Tests - Water
7:38
Organic Analysis: Classical Methods
10:51
Classical Methods of Structure Identification: Solubility Tests - 5% aq. HCl Basic FG (Amines)
10:52
Organic Analysis: Classical Methods
11:50
Classical Methods of Structure Identification: Solubility Tests - 5% aq. NaOH Acidic FG (Carboxylic Acids, Phenols)
11:51
Organic Analysis: Classical Methods
13:28
Classical Methods of Structure Identification: Solubility Tests - 5% aq. NaHCO3 Strongly Acidic FG (Carboxylic Acids)
13:29
Organic Analysis: Classical Methods
15:35
Classical Methods of Structure Identification: Solubility Tests - Insoluble in All of the Above
15:36
Organic Analysis: Classical Methods
16:49
Classical Methods of Structure Identification: Idoform Test for Methyl Ketones
16:50
Organic Analysis: Classical Methods
22:02
Classical Methods of Structure Identification: Tollens' Test or Fehling's Solution for Aldehydes
22:03
Organic Analysis: Classical Methods
25:01
Useful Application of Classical Methods: Glucose Oxidase on Glucose Test Strips
25:02
Organic Analysis: Classical Methods
26:26
Classical Methods of Structure Identification: Starch-iodide Test
26:27
Organic Analysis: Classical Methods
28:22
Classical Methods of Structure Identification: Lucas Reagent to Determine Primary/Secondary/Tertiary Alcohol
28:23
Organic Analysis: Classical Methods
31:35
Classical Methods of Structure Identification: Silver Nitrate Test for Alkyl Halides
31:36
Organic Analysis: Classical Methods
33:23
Preparation of Derivatives
33:24
Organic Analysis: Modern Methods
36:55
Modern Methods of Chemical Characterization
36:56
Organic Analysis: Modern Methods
40:36
Checklist for Manuscripts Submitted to the ACS Journal Organic Letters
40:37
Organic Analysis: Modern Methods
42:39
Checklist for Manuscripts Submitted to the ACS Journal Organic Letters
42:40
Analysis of Stereochemistry

1h 2m 52s

Intro
0:00
Chirality & Optical Activity
0:32
Levorotatory & Dextrorotatory
0:33
Example: Optically Active?
2:22
Example: Optically Active?
2:23
Measurement of Specific Rotation, [α]
5:09
Measurement of Specific Rotation, [α]
5:10
Example: Calculation of Specific Rotation
8:56
Example: Calculation of Specific Rotation
8:57
Variability of Specific Rotation, [α]
12:52
Variability of Specific Rotation, [α]
12:53
Other Measures of Optical Activity: ORD and CD
15:04
Optical Rotary Dispersion (ORD)
15:05
Circular Dischroism (CD)
18:32
Circular Dischroism (CD)
18:33
Mixtures of Enantiomers
20:16
Racemic Mixtures
20:17
Unequal Mixtures of Enantiomers
21:36
100% ee
22:48
0% ee
23:34
Example: Definition of ee?
24:00
Example: Definition of ee?
24:01
Analysis of Optical Purity: [α]
27:47
[α] Measurement Can Be Used for Known Compounds
27:48
Analysis of Optical Purity: [α]
34:30
NMR Methods Using a Chiral Derivatizing Agent (CDA): Mosher's Reagent
34:31
Analysis of Optical Purity: [α]
40:01
NMR Methods Using a Chiral Derivatizing Agent (CDA): CDA Salt Formation
40:02
Analysis of Optical Purity: Chromatography
42:46
Chiral Chromatography
42:47
Stereochemistry Analysis by NMR: J Values (Coupling Constant)
51:28
NMR Methods for Structure Determination
51:29
Stereochemistry Analysis by NRM: NOE
57:00
NOE - Nuclear Overhauser Effect ( 2D Versions: NOESY or ROESY)
57:01
XIII. Spectroscopy
Infrared Spectroscopy, Part I

1h 4m

Intro
0:00
Infrared (IR) Spectroscopy
0:09
Introduction to Infrared (IR) Spectroscopy
0:10
Intensity of Absorption Is Proportional to Change in Dipole
3:08
IR Spectrum of an Alkane
6:08
Pentane
6:09
IR Spectrum of an Alkene
13:12
1-Pentene
13:13
IR Spectrum of an Alkyne
15:49
1-Pentyne
15:50
IR Spectrum of an Aromatic Compound
18:02
Methylbenzene
18:24
IR of Substituted Aromatic Compounds
24:04
IR of Substituted Aromatic Compounds
24:05
IR Spectrum of 1,2-Disubstituted Aromatic
25:30
1,2-dimethylbenzene
25:31
IR Spectrum of 1,3-Disubstituted Aromatic
27:15
1,3-dimethylbenzene
27:16
IR Spectrum of 1,4-Disubstituted Aromatic
28:41
1,4-dimethylbenzene
28:42
IR Spectrum of an Alcohol
29:34
1-pentanol
29:35
IR Spectrum of an Amine
32:39
1-butanamine
32:40
IR Spectrum of a 2° Amine
34:50
Diethylamine
34:51
IR Spectrum of a 3° Amine
35:47
Triethylamine
35:48
IR Spectrum of a Ketone
36:41
2-butanone
36:42
IR Spectrum of an Aldehyde
40:10
Pentanal
40:11
IR Spectrum of an Ester
42:38
Butyl Propanoate
42:39
IR Spectrum of a Carboxylic Acid
44:26
Butanoic Acid
44:27
Sample IR Correlation Chart
47:36
Sample IR Correlation Chart: Wavenumber and Functional Group
47:37
Predicting IR Spectra: Sample Structures
52:06
Example 1
52:07
Example 2
53:29
Example 3
54:40
Example 4
57:08
Example 5
58:31
Example 6
59:07
Example 7
1:00:52
Example 8
1:02:20
Infrared Spectroscopy, Part II

48m 34s

Intro
0:00
Interpretation of IR Spectra: a Basic Approach
0:05
Interpretation of IR Spectra: a Basic Approach
0:06
Other Peaks to Look for
3:39
Examples
5:17
Example 1
5:18
Example 2
9:09
Example 3
11:52
Example 4
14:03
Example 5
16:31
Example 6
19:31
Example 7
22:32
Example 8
24:39
IR Problems Part 1
28:11
IR Problem 1
28:12
IR Problem 2
31:14
IR Problem 3
32:59
IR Problem 4
34:23
IR Problem 5
35:49
IR Problem 6
38:20
IR Problems Part 2
42:36
IR Problem 7
42:37
IR Problem 8
44:02
IR Problem 9
45:07
IR Problems10
46:10
Nuclear Magnetic Resonance (NMR) Spectroscopy, Part I

1h 32m 14s

Intro
0:00
Purpose of NMR
0:14
Purpose of NMR
0:15
How NMR Works
2:17
How NMR Works
2:18
Information Obtained From a ¹H NMR Spectrum
5:51
No. of Signals, Integration, Chemical Shifts, and Splitting Patterns
5:52
Number of Signals in NMR (Chemical Equivalence)
7:52
Example 1: How Many Signals in ¹H NMR?
7:53
Example 2: How Many Signals in ¹H NMR?
9:36
Example 3: How Many Signals in ¹H NMR?
12:15
Example 4: How Many Signals in ¹H NMR?
13:47
Example 5: How Many Signals in ¹H NMR?
16:12
Size of Signals in NMR (Peak Area or Integration)
21:23
Size of Signals in NMR (Peak Area or Integration)
21:24
Using Integral Trails
25:15
Example 1: C₈H₁₈O
25:16
Example 2: C₃H₈O
27:17
Example 3: C₇H₈
28:21
Location of NMR Signal (Chemical Shift)
29:05
Location of NMR Signal (Chemical Shift)
29:06
¹H NMR Chemical Shifts
33:20
¹H NMR Chemical Shifts
33:21
¹H NMR Chemical Shifts (Protons on Carbon)
37:03
¹H NMR Chemical Shifts (Protons on Carbon)
37:04
Chemical Shifts of H's on N or O
39:01
Chemical Shifts of H's on N or O
39:02
Estimating Chemical Shifts
41:13
Example 1: Estimating Chemical Shifts
41:14
Example 2: Estimating Chemical Shifts
43:22
Functional Group Effects are Additive
45:28
Calculating Chemical Shifts
47:38
Methylene Calculation
47:39
Methine Calculation
48:20
Protons on sp³ Carbons: Chemical Shift Calculation Table
48:50
Example: Estimate the Chemical Shift of the Selected H
50:29
Effects of Resonance on Chemical Shifts
53:11
Example 1: Effects of Resonance on Chemical Shifts
53:12
Example 2: Effects of Resonance on Chemical Shifts
55:09
Example 3: Effects of Resonance on Chemical Shifts
57:08
Shape of NMR Signal (Splitting Patterns)
59:17
Shape of NMR Signal (Splitting Patterns)
59:18
Understanding Splitting Patterns: The 'n+1 Rule'
1:01:24
Understanding Splitting Patterns: The 'n+1 Rule'
1:01:25
Explanation of n+1 Rule
1:02:42
Explanation of n+1 Rule: One Neighbor
1:02:43
Explanation of n+1 Rule: Two Neighbors
1:06:23
Summary of Splitting Patterns
1:06:24
Summary of Splitting Patterns
1:10:45
Predicting ¹H NMR Spectra
1:10:46
Example 1: Predicting ¹H NMR Spectra
1:13:30
Example 2: Predicting ¹H NMR Spectra
1:19:07
Example 3: Predicting ¹H NMR Spectra
1:23:50
Example 4: Predicting ¹H NMR Spectra
1:29:27
Nuclear Magnetic Resonance (NMR) Spectroscopy, Part II

2h 3m 48s

Intro
0:00
¹H NMR Problem-Solving Strategies
0:18
Step 1: Analyze IR Spectrum (If Provided)
0:19
Step 2: Analyze Molecular Formula (If Provided)
2:06
Step 3: Draw Pieces of Molecule
3:49
Step 4: Confirm Pieces
6:30
Step 5: Put the Pieces Together!
7:23
Step 6: Check Your Answer!
8:21
Examples
9:17
Example 1: Determine the Structure of a C₉H₁₀O₂ Compound with the Following ¹H NMR Data
9:18
Example 2: Determine the Structure of a C₉H₁₀O₂ Compound with the Following ¹H NMR Data
17:27
¹H NMR Practice
20:57
¹H NMR Practice 1: C₁₀H₁₄
20:58
¹H NMR Practice 2: C₄H₈O₂
29:50
¹H NMR Practice 3: C₆H₁₂O₃
39:19
¹H NMR Practice 4: C₈H₁₈
50:19
More About Coupling Constants (J Values)
57:11
Vicinal (3-bond) and Geminal (2-bond)
57:12
Cyclohexane (ax-ax) and Cyclohexane (ax-eq) or (eq-eq)
59:50
Geminal (Alkene), Cis (Alkene), and Trans (Alkene)
1:02:40
Allylic (4-bond) and W-coupling (4-bond) (Rigid Structures Only)
1:04:05
¹H NMR Advanced Splitting Patterns
1:05:39
Example 1: ¹H NMR Advanced Splitting Patterns
1:05:40
Example 2: ¹H NMR Advanced Splitting Patterns
1:10:01
Example 3: ¹H NMR Advanced Splitting Patterns
1:13:45
¹H NMR Practice
1:22:53
¹H NMR Practice 5: C₁₁H₁₇N
1:22:54
¹H NMR Practice 6: C₉H₁₀O
1:34:04
¹³C NMR Spectroscopy
1:44:49
¹³C NMR Spectroscopy
1:44:50
¹³C NMR Chemical Shifts
1:47:24
¹³C NMR Chemical Shifts Part 1
1:47:25
¹³C NMR Chemical Shifts Part 2
1:48:59
¹³C NMR Practice
1:50:16
¹³C NMR Practice 1
1:50:17
¹³C NMR Practice 2
1:58:30
C-13 DEPT NMR Experiments

23m 10s

Intro
0:00
C-13 DEPT NMR Spectoscopy
0:13
Overview
0:14
C-13 DEPT NMR Spectoscopy, Cont.
3:31
Match C-13 Peaks to Carbons on Structure
3:32
C-13 DEPT NMR Spectoscopy, Cont.
8:46
Predict the DEPT-90 and DEPT-135 Spectra for the Given Compound
8:47
C-13 DEPT NMR Spectoscopy, Cont.
12:30
Predict the DEPT-90 and DEPT-135 Spectra for the Given Compound
12:31
C-13 DEPT NMR Spectoscopy, Cont.
17:19
Determine the Structure of an Unknown Compound using IR Spectrum and C-13 DEPT NMR
17:20
Two-Dimensional NMR Techniques: COSY

33m 39s

Intro
0:00
Two-Dimensional NMR Techniques: COSY
0:14
How Do We Determine Which Protons are Related in the NMR?
0:15
Two-Dimensional NMR Techniques: COSY
1:48
COSY Spectra
1:49
Two-Dimensional NMR Techniques: COSY
7:00
COSY Correlation
7:01
Two-Dimensional NMR Techniques: COSY
8:55
Complete the COSY NMR Spectrum for the Given Compoun
8:56
NMR Practice Problem
15:40
Provide a Structure for the Unknown Compound with the H NMR and COSY Spectra Shown
15:41
Two-Dimensional NMR Techniques: HETCOR & HMBC

15m 5s

Intro
0:00
HETCOR
0:15
Heteronuclear Correlation Spectroscopy
0:16
HETCOR
2:04
HETCOR Example
2:05
HMBC
11:07
Heteronuclear Multiple Bond Correlation
11:08
HMBC
13:14
HMB Example
13:15
Mass Spectrometry

1h 28m 35s

Intro
0:00
Introduction to Mass Spectrometry
0:37
Uses of Mass Spectrometry: Molecular Mass
0:38
Uses of Mass Spectrometry: Molecular Formula
1:04
Uses of Mass Spectrometry: Structural Information
1:21
Uses of Mass Spectrometry: In Conjunction with Gas Chromatography
2:03
Obtaining a Mass Spectrum
2:59
Obtaining a Mass Spectrum
3:00
The Components of a Mass Spectrum
6:44
The Components of a Mass Spectrum
6:45
What is the Mass of a Single Molecule
12:13
Example: CH₄
12:14
Example: ¹³CH₄
12:51
What Ratio is Expected for the Molecular Ion Peaks of C₂H₆?
14:20
Other Isotopes of High Abundance
16:30
Example: Cl Atoms
16:31
Example: Br Atoms
18:33
Mass Spectrometry of Chloroethane
19:22
Mass Spectrometry of Bromobutane
21:23
Isotopic Abundance can be Calculated
22:48
What Ratios are Expected for the Molecular Ion Peaks of CH₂Br₂?
22:49
Determining Molecular Formula from High-resolution Mass Spectrometry
26:53
Exact Masses of Various Elements
26:54
Fragmentation of various Functional Groups
28:42
What is More Stable, a Carbocation C⁺ or a Radical R?
28:43
Fragmentation is More Likely If It Gives Relatively Stable Carbocations and Radicals
31:37
Mass Spectra of Alkanes
33:15
Example: Hexane
33:16
Fragmentation Method 1
34:19
Fragmentation Method 2
35:46
Fragmentation Method 3
36:15
Mass of Common Fragments
37:07
Mass of Common Fragments
37:08
Mass Spectra of Alkanes
39:28
Mass Spectra of Alkanes
39:29
What are the Peaks at m/z 15 and 71 So Small?
41:01
Branched Alkanes
43:12
Explain Why the Base Peak of 2-methylhexane is at m/z 43 (M-57)
43:13
Mass Spectra of Alkenes
45:42
Mass Spectra of Alkenes: Remove 1 e⁻
45:43
Mass Spectra of Alkenes: Fragment
46:14
High-Energy Pi Electron is Most Likely Removed
47:59
Mass Spectra of Aromatic Compounds
49:01
Mass Spectra of Aromatic Compounds
49:02
Mass Spectra of Alcohols
51:32
Mass Spectra of Alcohols
51:33
Mass Spectra of Ethers
54:53
Mass Spectra of Ethers
54:54
Mass Spectra of Amines
56:49
Mass Spectra of Amines
56:50
Mass Spectra of Aldehydes & Ketones
59:23
Mass Spectra of Aldehydes & Ketones
59:24
McLafferty Rearrangement
1:01:29
McLafferty Rearrangement
1:01:30
Mass Spectra of Esters
1:04:15
Mass Spectra of Esters
1:01:16
Mass Spectrometry Discussion I
1:05:01
For the Given Molecule (M=58), Do You Expect the More Abundant Peak to Be m/z 15 or m/z 43?
1:05:02
Mass Spectrometry Discussion II
1:08:13
For the Given Molecule (M=74), Do You Expect the More Abundant Peak to Be m/z 31, m/z 45, or m/z 59?
1:08:14
Mass Spectrometry Discussion III
1:11:42
Explain Why the Mass Spectra of Methyl Ketones Typically have a Peak at m/z 43
1:11:43
Mass Spectrometry Discussion IV
1:14:46
In the Mass Spectrum of the Given Molecule (M=88), Account for the Peaks at m/z 45 and m/z 57
1:14:47
Mass Spectrometry Discussion V
1:18:25
How Could You Use Mass Spectrometry to Distinguish Between the Following Two Compounds (M=73)?
1:18:26
Mass Spectrometry Discussion VI
1:22:45
What Would be the m/z Ratio for the Fragment for the Fragment Resulting from a McLafferty Rearrangement for the Following Molecule (M=114)?
1:22:46
XIV. Organic Chemistry Lab
Completing the Reagent Table for Prelab

21m 9s

Intro
0:00
Sample Reagent Table
0:11
Reagent Table Overview
0:12
Calculate Moles of 2-bromoaniline
6:44
Calculate Molar Amounts of Each Reagent
9:20
Calculate Mole of NaNO₂
9:21
Calculate Moles of KI
10:33
Identify the Limiting Reagent
11:17
Which Reagent is the Limiting Reagent?
11:18
Calculate Molar Equivalents
13:37
Molar Equivalents
13:38
Calculate Theoretical Yield
16:40
Theoretical Yield
16:41
Calculate Actual Yield (%Yield)
18:30
Actual Yield (%Yield)
18:31
Introduction to Melting Points

16m 10s

Intro
0:00
Definition of a Melting Point (mp)
0:04
Definition of a Melting Point (mp)
0:05
Solid Samples Melt Gradually
1:49
Recording Range of Melting Temperature
2:04
Melting Point Theory
3:14
Melting Point Theory
3:15
Effects of Impurities on a Melting Point
3:57
Effects of Impurities on a Melting Point
3:58
Special Exception: Eutectic Mixtures
5:09
Freezing Point Depression by Solutes
5:39
Melting Point Uses
6:19
Solid Compound
6:20
Determine Purity of a Sample
6:42
Identify an Unknown Solid
7:06
Recording a Melting Point
9:03
Pack 1-3 mm of Dry Powder in MP Tube
9:04
Slowly Heat Sample
9:55
Record Temperature at First Sign of Melting
10:33
Record Temperature When Last Crystal Disappears
11:26
Discard MP Tube in Glass Waste
11:32
Determine Approximate MP
11:42
Tips, Tricks and Warnings
12:28
Use Small, Tightly Packed Sample
12:29
Be Sure MP Apparatus is Cool
12:45
Never Reuse a MP Tube
13:16
Sample May Decompose
13:30
If Pure Melting Point (MP) Doesn't Match Literature
14:20
Melting Point Lab

8m 17s

Intro
0:00
Melting Point Tubes
0:40
Melting Point Apparatus
3:42
Recording a melting Point
5:50
Introduction to Recrystallization

22m

Intro
0:00
Crystallization to Purify a Solid
0:10
Crude Solid
0:11
Hot Solution
0:20
Crystals
1:09
Supernatant Liquid
1:20
Theory of Crystallization
2:34
Theory of Crystallization
2:35
Analysis and Obtaining a Second Crop
3:40
Crystals → Melting Point, TLC
3:41
Supernatant Liquid → Crude Solid → Pure Solid
4:18
Crystallize Again → Pure Solid (2nd Crop)
4:32
Choosing a Solvent
5:19
1. Product is Very Soluble at High Temperatures
5:20
2. Product has Low Solubility at Low Temperatures
6:00
3. Impurities are Soluble at All Temperatures
6:16
Check Handbooks for Suitable Solvents
7:33
Why Isn't This Dissolving?!
8:46
If Solid Remains When Solution is Hot
8:47
Still Not Dissolved in Hot Solvent?
10:18
Where Are My Crystals?!
12:23
If No Crystals Form When Solution is Cooled
12:24
Still No Crystals?
14:59
Tips, Tricks and Warnings
16:26
Always Use a Boiling Chip or Stick!
16:27
Use Charcoal to Remove Colored Impurities
16:52
Solvent Pairs May Be Used
18:23
Product May 'Oil Out'
20:11
Recrystallization Lab

19m 7s

Intro
0:00
Step 1: Dissolving the Solute in the Solvent
0:12
Hot Filtration
6:33
Step 2: Cooling the Solution
8:01
Step 3: Filtering the Crystals
12:08
Step 4: Removing & Drying the Crystals
16:10
Introduction to Distillation

25m 54s

Intro
0:00
Distillation: Purify a Liquid
0:04
Simple Distillation
0:05
Fractional Distillation
0:55
Theory of Distillation
1:04
Theory of Distillation
1:05
Vapor Pressure and Volatility
1:52
Vapor Pressure
1:53
Volatile Liquid
2:28
Less Volatile Liquid
3:09
Vapor Pressure vs. Boiling Point
4:03
Vapor Pressure vs. Boiling Point
4:04
Increasing Vapor Pressure
4:38
The Purpose of Boiling Chips
6:46
The Purpose of Boiling Chips
6:47
Homogeneous Mixtures of Liquids
9:24
Dalton's Law
9:25
Raoult's Law
10:27
Distilling a Mixture of Two Liquids
11:41
Distilling a Mixture of Two Liquids
11:42
Simple Distillation: Changing Vapor Composition
12:06
Vapor & Liquid
12:07
Simple Distillation: Changing Vapor Composition
14:47
Azeotrope
18:41
Fractional Distillation: Constant Vapor Composition
19:42
Fractional Distillation: Constant Vapor Composition
19:43
Distillation Lab

24m 13s

Intro
0:00
Glassware Overview
0:04
Heating a Sample
3:09
Bunsen Burner
3:10
Heating Mantle 1
4:45
Heating Mantle 2
6:18
Hot Plate
7:10
Simple Distillation Lab
8:37
Fractional Distillation Lab
17:13
Removing the Distillation Set-Up
22:41
Introduction to TLC (Thin-Layer Chromatography)

28m 51s

Intro
0:00
Chromatography
0:06
Purification & Analysis
0:07
Types of Chromatography: Thin-layer, Column, Gas, & High Performance Liquid
0:24
Theory of Chromatography
0:44
Theory of Chromatography
0:45
Performing a Thin-layer Chromatography (TLC) Analysis
2:30
Overview: Thin-layer Chromatography (TLC) Analysis
2:31
Step 1: 'Spot' the TLC Plate
4:11
Step 2: Prepare the Developing Chamber
5:54
Step 3: Develop the TLC Plate
7:30
Step 4: Visualize the Spots
9:02
Step 5: Calculate the Rf for Each Spot
12:00
Compound Polarity: Effect on Rf
16:50
Compound Polarity: Effect on Rf
16:51
Solvent Polarity: Effect on Rf
18:47
Solvent Polarity: Effect on Rf
18:48
Example: EtOAc & Hexane
19:35
Other Types of Chromatography
22:27
Thin-layer Chromatography (TLC)
22:28
Column Chromatography
22:56
High Performance Liquid (HPLC)
23:59
Gas Chromatography (GC)
24:38
Preparative 'prep' Scale Possible
28:05
TLC Analysis Lab

20m 50s

Intro
0:00
Step 1: 'Spot' the TLC Plate
0:06
Step 2: Prepare the Developing Chamber
4:06
Step 3: Develop the TLC Plate
6:26
Step 4: Visualize the Spots
7:45
Step 5: Calculate the Rf for Each Spot
11:48
How to Make Spotters
12:58
TLC Plate
16:04
Flash Column Chromatography
17:11
Introduction to Extractions

34m 25s

Intro
0:00
Extraction Purify, Separate Mixtures
0:07
Adding a Second Solvent
0:28
Mixing Two Layers
0:38
Layers Settle
0:54
Separate Layers
1:05
Extraction Uses
1:20
To Separate Based on Difference in Solubility/Polarity
1:21
To Separate Based on Differences in Reactivity
2:11
Separate & Isolate
2:20
Theory of Extraction
3:03
Aqueous & Organic Phases
3:04
Solubility: 'Like Dissolves Like'
3:25
Separation of Layers
4:06
Partitioning
4:14
Distribution Coefficient, K
5:03
Solutes Partition Between Phases
5:04
Distribution Coefficient, K at Equilibrium
6:27
Acid-Base Extractions
8:09
Organic Layer
8:10
Adding Aqueous HCl & Mixing Two Layers
8:46
Neutralize (Adding Aqueous NaOH)
10:05
Adding Organic Solvent Mix Two Layers 'Back Extract'
10:24
Final Results
10:43
Planning an Acid-Base Extraction, Part 1
11:01
Solute Type: Neutral
11:02
Aqueous Solution: Water
13:40
Solute Type: Basic
14:43
Solute Type: Weakly Acidic
15:23
Solute Type: Acidic
16:12
Planning an Acid-Base Extraction, Part 2
17:34
Planning an Acid-Base Extraction
17:35
Performing an Extraction
19:34
Pour Solution into Sep Funnel
19:35
Add Second Liquid
20:07
Add Stopper, Cover with Hand, Remove from Ring
20:48
Tip Upside Down, Open Stopcock to Vent Pressure
21:00
Shake to Mix Two Layers
21:30
Remove Stopper & Drain Bottom Layer
21:40
Reaction Work-up: Purify, Isolate Product
22:03
Typical Reaction is Run in Organic Solvent
22:04
Starting a Reaction Work-up
22:33
Extracting the Product with Organic Solvent
23:17
Combined Extracts are Washed
23:40
Organic Layer is 'Dried'
24:23
Finding the Product
26:38
Which Layer is Which?
26:39
Where is My Product?
28:00
Tips, Tricks and Warnings
29:29
Leaking Sep Funnel
29:30
Caution When Mixing Layers & Using Ether
30:17
If an Emulsion Forms
31:51
Extraction Lab

14m 49s

Intro
0:00
Step 1: Preparing the Separatory Funnel
0:03
Step 2: Adding Sample
1:18
Step 3: Mixing the Two Layers
2:59
Step 4: Draining the Bottom Layers
4:59
Step 5: Performing a Second Extraction
5:50
Step 6: Drying the Organic Layer
7:21
Step 7: Gravity Filtration
9:35
Possible Extraction Challenges
12:55
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Lecture Comments (96)

1 answer

Last reply by: Professor Starkey
Fri Jun 22, 2018 1:39 AM

Post by Kojo Asiedu on June 16 at 08:59:50 AM

How can I get help. The lectures are not responding. I am very frustrated because I have an exam and when I needed the site most I cant access it. It is very difficult to get help on this site

1 answer

Last reply by: Professor Starkey
Tue May 1, 2018 12:08 AM

Post by Arrhenius Theory on April 27 at 09:28:30 PM

It is true that the hydrogen atom is always considered to be the lowest priority group in R and S nomenclature. Also, I would like to state whether or not if the hydrogen atom which is pointing away from the viewer follows the Cahn Ingold Prelog Convention, hence the direction of R and S nomenclature should not be reversed. Furthermore, it would suggest that it supports the Cahn Ingold Prelog convention and therefore the path in the R and S configuration should not be changed.

1 answer

Last reply by: Professor Starkey
Wed Dec 30, 2015 10:55 AM

Post by Shih-Kuan Chen on December 29, 2015

Hello Professor,
Your lectures are fantastic and I wanted to thank you for that.
To determine whether or not a carbon is chiral, we have to see if all 4 "groups" attached are different from one another. Does that mean, as long as the entire branch is different from each other, it is ok if the connecting atoms are the same?

Thanks

1 answer

Last reply by: Professor Starkey
Tue Dec 15, 2015 11:12 AM

Post by manu vats singh on December 15, 2015

which molecular model set you use

1 answer

Last reply by: Professor Starkey
Tue Nov 17, 2015 1:05 AM

Post by Anurag Agrawal on November 16, 2015

at 61:27 how do you know both bromine and chlorine are on the left for molecule C and both on the right for molecule D?

1 answer

Last reply by: Professor Starkey
Sun Oct 4, 2015 11:03 PM

Post by CHARLES AGU on October 4, 2015

Hello, please what would you call the relationship between two superimposable mirror images of structures with 4 different groups each? I'm performing a dry lab using my model kit (the structures were enantiomers at first but when I switched two of the groups on the mirror image, it became identical and superimposable with the original structure). Thanks.

1 answer

Last reply by: Professor Starkey
Sat Oct 3, 2015 7:36 PM

Post by CHARLES AGU on October 3, 2015

How do I fast forward or go to the subsection I want in the lecture?

1 answer

Last reply by: Professor Starkey
Wed Aug 26, 2015 10:21 AM

Post by Rafael Mojica on August 25, 2015

Hello,

When you number the carbon chain the place where you select #! is it random or are there any rules involved with the direction of the numbering?

Thanks!

1 answer

Last reply by: Professor Starkey
Sat Apr 11, 2015 6:01 PM

Post by Jason Smith on April 10, 2015

Just to keep things clear in my mind: chiral molecules are always non-superimposable and achiral molecules are always superimposable, right? Thank you professor.

2 answers

Last reply by: Professor Starkey
Sun Mar 22, 2015 11:10 PM

Post by Andres Lojano Bermeo on March 21, 2015

Hello Professor, on minute 53:19, you mention that the configuration is (2R,3R) 2-bromo-3chloropentane, shouldn't the 3R be a 3S, since it is going counter clock-wise to the #4 hydrogen? Or is that incorrect?

1 answer

Last reply by: Professor Starkey
Fri Dec 5, 2014 1:13 AM

Post by Camille Fraser on December 4, 2014

When drawing (S)-2-bromopentane shouldn't it start from the CH3 instead of the CH2?

1 answer

Last reply by: Professor Starkey
Fri Dec 5, 2014 1:15 AM

Post by Camille Fraser on December 4, 2014

In 33:07 in Nomenclature why is the Y shaped structure considered number 1, how did you get C,C H?

1 answer

Last reply by: Professor Starkey
Sun Oct 26, 2014 12:51 AM

Post by Foaad Zaid on October 23, 2014

if we had a c=c double bond, and each of the substituents on the carbons were all different groups, would that molecule be chiral? We have no stereocenters, however it extremely unsymmetrical? Thank you.

1 answer

Last reply by: Professor Starkey
Sun Oct 26, 2014 12:49 AM

Post by Foaad Zaid on October 23, 2014

hello, at 99: 13 you said that 25% and 25% combine to make a racemic mixture. do you mind just explaining that? Thank you.

1 answer

Last reply by: Professor Starkey
Sun Oct 26, 2014 12:46 AM

Post by Foaad Zaid on October 23, 2014

hello, at 20:05, for the cis-1,3 disubstituted cyclohexane, are you saying that the the molecule itself is achiral? Is the mirror meant to depict the relationship between 2 different molecules or meant to depict the plane of symmetry in just ONE cis- 1,3 disubstituted cyclohexane? Because to me, if we were to treat the molecules on each side of the mirror as separate molecules, they would be enantiomers of eachother correct? Thank you in advance.

1 answer

Last reply by: Professor Starkey
Mon Oct 20, 2014 11:55 PM

Post by Robert Rakowski on October 20, 2014

Hello Dr. Starkey,

What makes a carbon a chirality center? I understand that it would need to have four different groups but at 18 min in the second example why wouldn't the other carbons be chirality centers? They would have 4 different groups (c,h,h,h) (c,h,h)so why is the carbon with the chlorine a chirality center and the others are not?  

1 answer

Last reply by: Professor Starkey
Tue Oct 14, 2014 12:37 AM

Post by Celeste Shefferly on October 13, 2014

Do you cover polarimetry in any of your lectures?

1 answer

Last reply by: linda chy
Sun Oct 12, 2014 2:36 PM

Post by linda chy on October 12, 2014

you are amazing!!!. i was completely blank when this was being thought in class buy my prof,but it makes so much sense now. Thank you very much:)

1 answer

Last reply by: Professor Starkey
Sat Sep 27, 2014 2:34 PM

Post by Kevin Golden on September 26, 2014

You are amazing!!!

1 answer

Last reply by: Professor Starkey
Tue Sep 9, 2014 11:45 PM

Post by Nadia A on September 9, 2014

Hi Educator,
Is there a way to fast forward through lectures, or does the system not allow this? Thx!!

0 answers

Post by Nadia Ariqat on September 9, 2014

In my opinion, stereochem is one of the more confusing topics within organic chemistry (and where a lot of us make mistakes when we're first starting out). Drawing the correct fischer projection has always been a bit challenging for me personally; but when you look at it from the perspective of the stick figure/laying down, it actually makes 100% sense. This is a great lecture..highly recommend it!!

0 answers

Post by somia abdelgawad on May 7, 2014

on 64 min also A and C are diastereomers

1 answer

Last reply by: Professor Starkey
Sat May 10, 2014 12:05 AM

Post by somia abdelgawad on May 7, 2014

you are amazing

1 answer

Last reply by: Professor Starkey
Fri Apr 4, 2014 9:27 AM

Post by lakshmi tatineni on April 3, 2014

How do i find the meso compounds in a question like this?
For the six isomers given below:

A. RRRR B. RRSS C. SSRR D. SSSS E. RSSR F. RSRS
a) Identify all enantiomer pairs? A and C , B and C
b) Identify all possible meso compounds ????
c) Identify all diastereomers of RRSS. all except B and C (would u include the mesocompounds too (i was thinking no but i have no clue))

Thank You

1 answer

Last reply by: Professor Starkey
Tue Apr 1, 2014 10:13 PM

Post by Sola Adeonigbagbe on April 1, 2014

Hi, Professor Starkey. Your lectures are very helpful, and its helping me learn Organic Chemistry in a much easier way. I have my exam in a few days, and this has been helping me not panic too much for the exam.

My question is when doing a Fishcer Projection for a molecule, I'm still a bit confused on how to determine whether a substituent is on my left side or my right side. Is there any particular way to determine it if one does not have the molecular kit to practice with? I know I have to look at each chiral carbon at an angle but it's still hard to know why say, bromide is on my left and chlorine is on my right. Thanks!

1 answer

Last reply by: Professor Starkey
Sat Mar 22, 2014 12:04 AM

Post by Johnny Green on March 20, 2014

At about the 47 minute mark you checked "R" and "S" configuration of the Fischer projection and the line drawing to see if they matched.  I understand that when the lowest priority group is pointing toward you (solid wedge) an S configuration is made an R configuration and vice versa.  If the lowest priority group is already facing in the plane (dash line) then an R configuration is an R and an S configuration remains an S.  You also said  that if you imagined laying down looking up the molecule that Cl would be on the left side and H would be on the right side. Why did you reverse the direction from S to R on the Fischer projection?  Isn't H already on a dashed line (facing away from you or facing in the plane)?

1 answer

Last reply by: Professor Starkey
Wed Mar 12, 2014 10:43 PM

Post by Richard Meador on March 12, 2014

on the Fischer projections (56:31), your stick figure lays down and looks up but how do you know the direction to orient his feet(right or left)?

1 answer

Last reply by: Professor Starkey
Thu Dec 5, 2013 11:36 PM

Post by bwalya nkonde on December 5, 2013

Hello, for the example about the molecules with 2 chiral centers, I am wondering how it is that you ended up with 3R, because it seems we rotated clockwise and not anti-clockwise?

1 answer

Last reply by: Professor Starkey
Mon Nov 11, 2013 10:05 AM

Post by Christina Elder on November 9, 2013

Hi Dr. Starkey,

With regard to enantiomers, I am confused about superimposability. From my understanding an enantiomers are molecules that are nonsuperimposable mirror images of each other. However, at minute 40:20 in the lecture, where you draw the enantiomer of the (S) 2-bromopentane by inverting the chiral centers, you mention that it is the same compound since they would line up nicely which is the same as superimposable. Is that correct? If so, why would it be considered an enantiomer if it is superimposable, or are they simply just the same compound. Thanks in advance for your help.

Christina

1 answer

Last reply by: Professor Starkey
Tue Sep 3, 2013 11:50 PM

Post by Donna maria on September 3, 2013

Sorry one more question. The enantiomer example. Isn't this superimposible? Therefore, can it be optically active? I thought achiral molecules could not or is thhis only for r/s configuration?

1 answer

Last reply by: Professor Starkey
Fri Aug 30, 2013 8:42 PM

Post by Donna maria on August 29, 2013

sorry. I understood the configuration R/S rule on the projection much better than the line drawing. So if i can convert to projections in exam, i should be fine. thank you.

1 answer

Last reply by: Professor Starkey
Fri Aug 30, 2013 8:48 PM

Post by Donna maria on August 29, 2013

Thank you, your lectures are amazing. I just have a question. Set A example. When you are outlining the second R configuration, I am confused why it is R? I can see that number 1 priority should be Cl (higher atomic number) but the others not labelled or have been omitted, I am unsure about, could you clarify just for peace of mind please?  

And also the location points of the dash lines. What determines the location of a dashed line as i can see that there have been numerous examples of different location points (left to the Br or right to the Cl). They are also mostly represented as hydrogen? Are they a another way of showing the side points on a tetrahedral? In addition, they are opposite to the wedges in terms of R/S configuration-is this a standard rule? So sorry for the questions!

1 answer

Last reply by: Professor Starkey
Tue Apr 23, 2013 3:54 PM

Post by Alicia DaSilva on April 23, 2013

Here is one of my homework questions: a chiral carbon has the following molecules attached to it:

1. CH(CH3)2
2. CH2CH2Br
3. CH2CH
4.H

Question, why does the CH(CH3)2 has a higher priority than CH2CH2Br?

1 answer

Last reply by: Professor Starkey
Fri Mar 29, 2013 1:51 AM

Post by ahmed alzeory on March 28, 2013

hello dr
for the nomenclature example the last one with hydrogen and bromide, how is it achiral even though the hydrogen and the bromide do not go within the line of symmetry?

1 answer

Last reply by: Professor Starkey
Thu Mar 7, 2013 11:11 AM

Post by Kristine Penalosa on March 6, 2013

Dr. Starkey,

Is there any way to put the slides in powerpoint format, so we can print the slides all at once?

Thanks for all the lectures!

1 answer

Last reply by: Professor Starkey
Sat Jan 26, 2013 9:45 PM

Post by marsha prytz on January 26, 2013

at 29:39 you are numbering the 4 groups attached to the chiral center. I was following until you got to the tie. You stated the end carbon with H,H,H was ranked #3 and the carbon #2 was ranked #2 group of the carbon because it had C,H,H. What I'm confused is why you didn't include the C with the 3 H's? Isn't there a carbon there?

1 answer

Last reply by: Professor Starkey
Sun Jan 6, 2013 1:21 PM

Post by wow love on January 6, 2013

Hi,

you said same physical property, what about chemical property?

1 answer

Last reply by: Professor Starkey
Sun Jan 6, 2013 1:20 PM

Post by wow love on January 6, 2013

Hi Dr. Starkey

In the 60 min when you were talking about fischer projection, I am kind of confuse about how to figure when the atom would be on your left or right??? I see the little stick figure you make however, how do one differentiate if a dash or wedge would be the atom on your left or right???

1 answer

Last reply by: Professor Starkey
Sun Dec 16, 2012 4:39 PM

Post by Susan McConnell on December 16, 2012

Hi Dr Starkey,
are there any lectures on Ramachandran plots and phi and psi angles? thanks

0 answers

Post by Alena Schwartsman on October 25, 2012

Lecture has to download completely to be able to skip around (there is loading bar at the bottom of a lecture video). After launching any lecture just wait for a few minutes and than skip around. Hope this helps.

3 answers

Last reply by: Professor Starkey
Sat Oct 26, 2013 9:59 PM

Post by Susan Reid on July 20, 2012

can you forward on the lecture?

2 answers

Last reply by: Eduardo Castaneda
Mon Jun 18, 2012 7:52 PM

Post by Eduardo Castaneda on June 15, 2012

Dr. Starkey

On example 4 for Nomenclature the Carbon that had 2 carbons, H, and Br attached to it. did you have to look at the CH3's that were next to the CH2's to determine that they were Identical?

For example, I saw that the Carbon had 4 groups attached to it. Out of these four groups 2 of them were the same the "CH2." I stopped there and determined that it was an achiral carbon. You however went forward and compared the groups next to them. Why did you compare the groups next to the CH2 which were the CH3's. Do you have to go further out?

Because lets say that the group on one of the CH2's had a "Cl" attached and on the other side the CH2 had a "N" attached to it. Would that then make it a chiral center?

Im just confused as to why you went further out and compared the groups that were next to the CH2. This then brings up the questions that I asked.

1 answer

Last reply by: Professor Starkey
Sun Apr 29, 2012 9:40 AM

Post by michelle daane on April 28, 2012

Dr. Starkey,
I'm confused... How is it that when evaluating a molecule for r/s that you can changed sides of the molecule top/bottom....? If I look at the structure and put 1 up, both br and cl are wedges so would be on the same side...., say the right...
When you have more than one arm on the fischer, do all of the arms come towards you or is it every other one ex; back and forth?
thanks

1 answer

Last reply by: Professor Starkey
Tue Mar 6, 2012 11:09 AM

Post by Michelle Gavin on March 2, 2012

you need to change the program so that you can move forward and backward within a session so you can navigate directly to the section that is of interest.

1 answer

Last reply by: Professor Starkey
Sun Nov 20, 2011 9:22 AM

Post by christopher coppins on November 13, 2011

hi Dr.Starkey im taking organic 1 an we are now on test #3 which is covering the topics of stereochemistry, alkyl halides, and reactions of alkyl halides.....i see the stereochemistry lecture but i just wanted to make sure for the alkyl lectures which lecture topic will that fall under, will it be the SN1 & SN2 lectures? an by the way thank you so much your the reason why im passing organic 1....

1 answer

Last reply by: Professor Starkey
Thu Oct 20, 2011 11:15 PM

Post by Ling Huang on October 10, 2011

This lecture was very helpful. I have some questions that I would like to clarify. I thought that enantiomers is chiral and is non-superimposable but for the example of the (S)-2-bromopentane, the mirror image of the (s)-2-bromopentane is superimposable. If I reverse the structure and put it on top of each other it is the same structure. Also, for nomenclature, does it have to be all different for the for bonds that is attached to the center C? Thank You for your help.

1 answer

Last reply by: David Fan
Thu Mar 14, 2013 1:49 PM

Post by ochemstarkey on February 25, 2011

Occurred to me while pushing into fullscreen mode, I cannot see the teacher in the corner of the screen. Any examples not shown on the writing pad are not seen while in full screen mode. Might be nice to be able to see the professor still while in full screen mode.

Stereochemistry

Label the following compound as chiral or achiral:
  • Draw the mirror image
  • Remember:
    All chiral objects have non-superimposable mirror images.
    All achiral object are exactly the same as their mirror images.
Achiral Molecule
Label the stereogenic center as R or S:
  • Rotate so the lowest priority group is oriented away from you:
  • Clockwise = R isomer
R
Draw the structure for the following compound:
(4R,5S)-4,5-diethyloctane
Give the IUPAC name for the following compound:
(4R,6R)-4ethyl-6-methyldecane
Draw all stereoisomers of: CH3CH(Cl)CH2CH(Br)CH3
Pure cholesterol has a specific rotation of -32. A sample of cholesterol has a specific rotation of -10. What is the enantiomeric excess of this sample?
  • ee = [([α] mixture)/([α] pure enantiomer)] ×100%
  • [(−10)/(−32)] ×100% = 0.3125 ×100 = 31.25%
31.25% ee

*These practice questions are only helpful when you work on them offline on a piece of paper and then use the solution steps function to check your answer.

Answer

Stereochemistry

Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.

  • Intro 0:00
  • Stereochemistry 0:10
    • Isomers
  • Stereoisomer Examples 1:30
    • Alkenes
    • Cycloalkanes
  • Stereoisomer Examples 4:00
    • Tetrahedral Carbon: Superimposable (Identical)
    • Tetrahedral Carbon: Non-Superimposable (Stereoisomers)
  • Chirality 7:18
    • Stereoisomers
    • Chiral
    • Achiral
    • Example: Achiral and Chiral
  • Chirality 20:11
    • Superimposable, Non-Superimposable, Chiral, and Achiral
  • Nomenclature 23:00
    • Cahn-Ingold-Prelog Rules
  • Nomenclature 29:39
    • Example 1: Nomenclature
    • Example 2: Nomenclature
    • Example 3: Nomenclature
    • Example 4: Nomenclature
  • Drawing Stereoisomers 36:58
    • Drawing (S)-2-bromopentane
    • Drawing the Enantiomer of (S)-2-bromopentane: Method 1
    • Drawing the Enantiomer of (S)-2-bromopentane: Method 2
  • Fischer Projections 41:47
    • Definition of Fischer Projections
    • Drawing Fischer Projection
    • Use of Fisher Projection: Assigning Configuration
  • Molecules with Two Chiral Carbons 51:49
    • Example A
    • Drawing Enantiomer of Example A
    • Fischer Projection of A
  • Drawing Stereoisomers, cont. 59:40
    • Drawing Stereoisomers Examples
    • Diastereomers
  • Drawing Stereoisomers 1:06:37
    • Draw All Stereoisomers of 2,3-dichlorobutane
  • Molecules with Two Chiral Centers 1:10:22
    • Draw All Stereoisomers of 2,3-dichlorobutane, cont.
  • Optical Activity 1:14:10
    • Chiral Molecules
    • Angle of Rotation
    • Achiral Species
  • Physical Properties of Stereoisomers 1:17:11
    • Enantiomers
    • Diastereomers
    • Example
  • Physical Properties of Stereoisomers 1:23:05
    • When Do Enantiomers Behave Differently?
  • Racemic Mixtures 1:28:18
    • Racemic Mixtures
    • Resolution
  • Unequal Mixtures of Enantiomers 1:32:54
    • Enantiomeric Excess (ee)
  • Unequal Mixture of Enantiomers 1:34:43
    • Unequal Mixture of Enantiomers
    • Example: Finding ee
    • Example: Percent of Composition

Transcription: Stereochemistry

Hi and welcome to Educator.0000

Our next topic is going to be that of stereochemistry; and that is where we take a look at organic molecules in three-dimensions--look at their shapes in space.0002

We've talked about isomers before; our original definition of isomers or the first way we were introduced to it is the idea of having two molecules who are related simply by their molecular formula.0012

They are different compounds, but they have the same formula; the atoms are put together differently--they have a different connectivity; and that is what makes them unique compounds.0023

Of course, they are different compounds because they are not interconvertible; and that is what makes them unique.0034

The original isomers we have our known as structural isomers or constitutional isomers; these are the ones with difference connectivity.0043

For example, these to alcohols are unique compounds; but because they have the same # of carbons, hydrogens, oxygens, they are defined as isomers of one another.0050

What we are going to look at next is the concept of having stereoisomers; stereoisomers again are described as isomers because they are not interconvertible and they are not identical.0060

But they have the same connectivity; all the atoms are put together in the same way and they differ by the arrangement space only.0074

Only when we look at their three-dimensional shape do we see a difference in their structures.0082

Let's take a look at a few examples.0087

For example if we have an alkene, we can have either the cis configuration or the trans configuration.0091

These different arrangements that we can have about the carbon-carbon double bond makes these two alkenes unique compounds; they are not superimposable; they are not identical.0099

Because rotation around this double bond is hindered--is prohibited, then we cannot simply flip them to be one side or the other.0111

We call it trans if they are on opposite sides and cis if they are on the same sides; and these are examples of stereoisomers.0121

They are the same # of carbons, hydrogens, oxygens, and so on--same formula; and they are even put together in the same order.0128

This is a one, two, three, four-carbon chain with a chlorine at carbon 2 and 3; and this is also a one, two, three, four-carbon chain with chlorines at carbon 2 and 3.0135

Only by look at their three-dimensional shape do we find a difference; these are called stereoisomers; sometimes, this is just called cis-trans isomerism.0148

Another example where we can have cis-trans isomerism is in the case of cycloalkanes when we have a ring.0156

Let's say we have two groups on a ring.0162

Here we have two methyl groups in the 1 and 3 position; here we also have two methyl groups in the 1 and 3 position; so both of these molecules will be named as 1,3-dimethylcyclohexane.0163

But again when we look at their three-dimensional shape, we see that they are unique compounds.0176

Because in this case, both methyl groups are pointing down, pointing away; and here we have one pointing down and one pointing up.0181

We use the same terminology here to describe cis and trans; we describe two groups on a ring as being cis to one another if they are on the same side of the ring.0189

If we flatten out the ring, you see that you can either be in the up position or the down position, either above the ring or below the ring.0201

Because these two substituents are on the same side of the ring, we would describe them as being cis to one another.0209

If they are on opposite sides of the ring, one up and one down, we would describe them as being trans to one another.0215

Once again these two molecules are unique compounds; they are not interconvertible.0222

In this case, it is because of the ring that free rotation around the sigma(σ) bonds are prohibited and we cannot interconvert between the two.0226

So cis and trans molecules are examples of stereoisomers.0235

Another interesting example of stereoisomers that we are going to be spending most of our time with in this section deals with a tetrahedral carbon.0242

An sp3 hybridized carbon that has four different groups attached; so four unique groups attached.0250

If I were to build such a carbon and then I were to build another carbon with the exact same four groups and I attached them in the exact same order.0257

In three dimensions I would see that I built two molecules that are identical; they are completely identical.0273

We could draw that on the page as saying: if I draw my tetrahedral carbon--if I have a red up here and a green down here and a blue as a wedge and a yellow as a dash.0279

These two molecules as drawn would be described as being superimposable; every atom on the first structure corresponds exactly with the atom on the second structure when you try and align these two.0293

That is another word for just saying they are identical.0309

But that is the test we are going to use to describe if two stereoisomers are identical--is if we can superimpose them.0312

Let me show you a little trick here: if I swap any two groups on here--let's take the red and the yellow and switch their positions.0319

When I do that and I try this same test and try to align them, all of sudden I find that the two tetrahedral carbons are no longer superimposable; they are no longer identical.0331

If I line up the blue and the green, then the red and the yellow don't match up.0342

If I line up the red and the blue, any two colors that I pick to line up, I will find that the other two colors don't align.0346

Now suddenly by doing this switch, we have come up with a new structure.0356

It doesn't matter which two groups you switch; you could try this at home.0365

Let's switch the red and the green but keep the blue and the yellow in the same position.0368

When we make that swap, we find that these two groups are now non-superimposable; they are unique compounds; they are stereoisomers of one another.0373

This now is going to be a little more challenging to see without working with models.0391

Eventually we are going to have to look at this 3D drawing and this 3D drawing and be able to tell by manipulating in our minds that in fact they are non-superimposable and they are unique compounds.0396

One more thing I want to demonstrate with these two tetrahedral carbons is they do in fact have a relationship you might be able to see.0410

It looks as if I had a mirror placed in between the two molecules; one would be the perfect reflection of the other; we describe these as having a mirror image relationship.0420

That is another relationship that is going to be very important to us in this chapter that we will come back to.0431

What makes a tetrahedral carbon with four unique groups on it have this special relationship of being non-superimposable with this mirror image is the fact that this molecule is a chiral molecule.0440

We need to discuss the term chirality and understand what that means; and then we will test out a few examples.0455

What we have just demonstrated is that stereoisomers are going to be possible for any tetrahedral carbon with four different groups attached; a lot of times we identify that carbon with an asterisk.0465

That carbon can be described as a chiral carbon or an asymmetric carbon or perhaps a chirality center.0478

What we will find is that when we have chiral objects, they are described as chiral because they have no mirror planes of symmetry; no internal planes of symmetry.0486

There are a few rare exceptions of highly symmetrical molecules that have no plane of symmetry but are still not chiral; but we are not going to come across any of those in our introductory lessons.0497

What we are going to look for is a plane of symmetry to describe whether or not something is chiral.0510

If an object does have a plane of symmetry, we are going to describe that molecule as being achiral; as achiral meaning not chiral.0517

Let's take a look at some sample molecules and see if we can determine whether or not they might be chiral or achiral--how about just a plain cyclohexane ring?0526

In cyclohexane, we know that it has various conformations; it can be a chair or a boat or a few different chairs.0539

But when it comes to looking for elements of symmetry, what we are going to do is we are going to totally flatten out these rings.0545

We are going to try and make them as symmetrical as possible before we look for symmetry.0551

Would you describe cyclohexane then as a symmetrical molecule?--does it have an internal plane of symmetry where one half of the molecule reflects on the other half?0555

Yes, in fact, this is a highly symmetrical molecule.0565

We can have a plane of symmetry that cuts straight through this molecule here; these three carbons reflect on these three carbons perfectly.0568

In fact, you can even have a plane of symmetry that slices through carbons and hydrogens; so one-half of this carbon atom reflects on the other half of this carbon.0577

The point is that the left-hand half of the molecule is the exact mirror image of the right-hand half.0587

So one example of an achiral molecule would be just something like a simple cyclohexane ring.0596

Now what if I were to put a substituent somewhere on the ring?--bromine, chlorine, something; now is this still a symmetrical molecule?0603

Clearly we have taken away some of the symmetry, but there is one plane of symmetry that still exists.0613

In fact I forgot to mention that we could even slice through for just cyclohexane, we can slice through all six carbons and that would be a plane of symmetry.0621

It reflects the six top hydrogens on the six bottom hydrogens.0630

So putting a substituent on the ring takes away that plane of symmetry.0636

But we still have one plane of internal symmetry right here; we can slice exactly through that atom and through these two carbons and those hydrogens and reflect this half onto this half.0639

Because it has a plane of symmetry, we describe this as an achiral molecule.0651

Maybe we could draw this as a ring with just either a wedge coming out or even a dash coming out; it doesn't matter how we draw that group.0658

How about looking at a carbon-carbon double bond such as this?--let's look at an alkene a carbon-carbon double bond.0668

Let's put one group on here; maybe again a chlorine or a bromine or maybe a methyl; something like that.0679

This is not a plane of symmetry and this would not be a plane of symmetry; this is not a plane of symmetry because it reflects a white atom onto a hydrogen.0687

But because this molecule is planar, we can use the plane of the molecule as a plane of symmetry slicing through every one of these atoms and reflecting the top half onto the bottom half.0694

So this in fact is also a symmetrical molecule; we describe this as an achiral molecule... so something like this; let's maybe put a CH3 here for example.0704

And this is planar so the plane of the molecule is going to act as the plane of symmetry.0720

A lot of times what we can do is we can draw... you could use a dashed line to indicate where the internal plane of symmetry is on the molecule; so there it is for the substituted cyclohexane.0726

And this one has a few planes of symmetry; we can go across this way or this way; and we can also have the plane of the molecule if we were to flatten it out.0737

How about having a six-membered ring with two groups on it?--does this still have a plane of symmetry?--well, in this case it does.0750

It has a plane of symmetry right here; and this is a plane of symmetry because we have an atom pointing towards you on the left and an atom pointing towards you on the right.0763

This would be as reflected on a mirror; so anything that is a wedge on one side would have to be a wedge on the other side; just like you would expect for a mirror image relationship.0774

So this too would be an example of an achiral molecule.0782

How about if I swapped one of these groups?--instead of looking at the cis disubstituted, how about the trans disubstituted?--now does this molecule still have a plane of symmetry?0794

Well it is a symmetrical molecule and a lot of times what you might recognize is that it has got a rotational symmetry; but that is not what we are looking for for chirality.0807

For chirality, we are looking for a plane of symmetry; an internal plane.0817

When we try and cut the molecule in half this way, we see that here we have a red atom reflecting up on the top and here that is reflecting on hydrogen.0821

This in fact does not have a plane of symmetry; so we would describe this molecule as a chiral molecule... as a chiral molecule.0831

So if we made one a wedge and one a dash, this now would be a chiral molecule.0842

Another example of a chiral molecule was this tetrahedral carbon that we saw, right?--because it has four unique groups0852

There is no plane of symmetry here because each group has no match to reflect onto.0860

We could write that down as an example of something that could be chiral--is a carbon with four different groups on it.0868

Remember we describe that as being a chiral carbon or an asymmetric carbon; and that is because it is an example of something that is chiral.0880

Another interesting example of something that is chiral is your hand; you will see this used in nearly every textbook that you refer to for organic chemistry.0888

Even though it is planar, the top half of your hand is different from the bottom half; your palm looks different and has different texture than the top half of your hand.0899

So this is also something that is described as chiral; and we will see some examples with that.0910

We can look for the symmetry in all sorts of different things besides molecules; like I said you could use your hand; you could also imagine maybe a chair0918

What if you had an ordinary chair with arms on both sides and the seat and the back?0927

That is something that is symmetrical; the left half looks exactly the same as the right half; so we could say that a chair is an example of something that is achiral.0933

How about if we compare that with a student desk that you might find in a classroom?0946

The student desk that has a chair but attached to it is a table, and it is usually attached to one side or the other side, right?--we have some right-handed desks; we have some left-handed desks.0951

That takes away the plane of symmetry; so a student desk is something that is also described as chiral.0962

One thing we want to know when we are studying stereochemistry is not only the definition of what it means to be chiral or achiral but then also to identify a given species as being chiral or achiral.0972

It is simply a matter of identifying internal planes of symmetry.0985

Let me show you something interesting about a molecule that is chiral or achiral.0990

Let's come back to our achiral molecule where we had the two groups pointing up right here; and let me draw its mirror image.0998

I am going to imagine a mirror here; and then I am going to try and draw the same structure and draw what I would see if I had a mirror here.1008

This pointing toward a mirror just like this one would be a wedge; and this one on the third carbon down we have another wedge; this would be the mirror image of this first structure.1017

Now let me ask what is the relationship of those two compounds?--if you had to describe the relationship of these two compounds, how would you describe them?1028

Let me build two of them and we can compare it.1039

Hopefully you see the mirror image relationship here, right?--they are mirror images of one another.1043

Are these two compounds superimposable?--are they identical?1048

Well sure; hopefully you can see that if I just picked this up and moved it over, I would in fact be able to match up every single atom on the first structure with the one on the second.1053

We describe this as being superimposable or identical... in other words, they are identical to one another.1061

Let's do the same thing with this second structure; so right here I have a molecule drawn where the one on the left is a wedge pointing up and the one on the right is a dash pointing down.1081

Then let's draw its mirror image; what does that mirror image look like?1097

We draw another cyclohexane ring; this one is the closest here; and pointing in this direction we have a dash; and then over here we have a wedge.1102

Now let's look at these two molecules again and ask what is their relationship?--what is the relationship?--are these superimposable?1113

This is where it gets to be a little challenging.1123

This is where working with models and getting plenty of practice is going to pay off because we are going to need to be able to see these relationships.1126

Here I have the model of these two; can I get them to superimpose?1137

If I do that same trick as before--if I lift it up and just try to lay them on top of each other.1140

I see they do not superimpose because here we see we have the red atom up and here we have the red atom down.1145

How about if I were to flip it?--can you imagine doing that?--let's try flipping it.1151

When I flip it, the same thing happens; I cannot get these to line up.1158

No matter what manipulations I do... remember you are free to rotate this around; but we are going to flatten it out and make it as symmetrical as possible.1162

These will not superimpose; these are unique compounds; these are non-superimposable.1169

These are called... we have a name for these; when you have a chiral object and you have a pair of non-superimposable mirror images--we call these enantiomers.1186

There is a lot of vocabulary in this stereochemistry unit; a lot of new terms and vocabulary that we will need to become familiar with.1199

A pair of non-superimposable mirror images are called enantiomers.1207

Let's look a little more closely at this and see if we can come up with some generalizations.1213

I've just redrawn what we drew by hand.1218

We said that these two molecules when we build them we confirm that they are in fact superimposable; while these two molecules when we build them we found that they are non-superimposable.1220

This is in fact a generality that we can determine dealing with chiral and a chiral; I am realizing right here that there is a little typo... let's compare a chiral to achiral.1232

If we have chiral objects, all chiral objects have non-superimposable mirror images.1250

Every time you have an object like this that we determine as chiral, it has no planes of symmetry; when we draw its mirror image or build its mirror image, it will always be non-superimposable.1256

In other words, every chiral molecule has an enantiomer; an enantiomer is something that exists for every chiral molecule.1267

All achiral objects, on the other hand, are exactly the same as their mirror image.1275

Because this molecule is achiral--it has this internal plane of symmetry, when we build its mirror image, we will always end up with the exact same molecule.1281

Again we can extend this to not just molecules like this, but we can extend it to the examples we saw on the previous page.1290

Imagine having a regular chair; if you were to build its mirror image and have a second chair sitting right next to it so that they are mirror images of each other. 2151 Would that be a different kind of chair or is it the exact same thing?--of course, it would be the exact same kind of chair.1299

In other words, an achiral molecule does not have an enantiomer; it does not have a unique mirror image; it is the same as its mirror image.1318

But if you had a right-handed student desk and you made its mirror image, that would be a new type of desk.1326

It would be a left-handed student desk; so that would be like the enantiomer of that original student desk.1333

This is where the example of the hand comes into play; and that is why you will always see it in the textbook--is because you have built in with you at all times a beautiful pair of enantiomers.1338

Disregarding any slight imperfections in your hands; imagining these are perfect mirror images of one another, they would in fact be non-superimposable.1349

Your right hand is unique from your left hand; and that is because this is a chiral object; it has no symmetry.1357

So when you built its mirror image which is what you have with your right and left hand... when you build its mirror image, you will end up with a unique compound.1364

Any time you are having trouble remembering what enantiomers are, remember that you have a little cheat sheet attached to your arms all the time.1372

Next let's talk about some nomenclature; how do we tell the world if these two molecules are different molecules?1382

Here we had our original pair of enantiomers that we built; we now know what to call these two molecules--mirror images; non-superimposable mirror images.1390

How do we tell the world that we are referring to this structure and not this structure?--we need some systematic nomenclature rules to describe this three-dimensional shape compared to this one.1400

What we are going to do is we are going to--for every chiral carbon that we find--so every tetrahedral carbon with four unique groups on it, we are going to name that as either an R or an S configuration.1419

Let's talk about the rules on how to determine whether it is R and S; and then we can look at several examples.1430

These are known as the Cahn-Ingold-Prelog rules; and our first step is that we need to assign priorities to the four groups; we need to prioritize them 1, 2, 3, and 4.1437

We are going to do this based on their atomic number; so we can just look at the four atoms attached and rank them 1, 2, 3, and 4; #1 is the highest atomic number; #4 is the lowest atomic number.1449

If you ever have a hydrogen attached to that chiral carbon, that of course would always be #4 because that is the lowest atomic number possible.1460

What if you have a tie--if you have two atoms that are identical that are attached to that tetrahedral carbon?1468

What you are going to do is you are going to move away one atom at a time until you find a difference; so you are going to try and break the tie; we will look at some examples of that.1473

If you encounter a double bond in your structure, you can treat that as if you had two separate single bonds; we will see some examples of that as well.1480

Our first goal is to rank the groups 1, 2, 3, 4; we are now going to view this chiral carbon with a very specific point of view.1487

We are going to take the #4 group; let's say this yellow is our lowest priority.1499

We are going to hold the molecule in such a way or view the molecule in such a way that the lowest priority group is pointing away from us; so it is a dashed bond.1503

When it is pointing away from us, we are going to move from group #1 to 2 to 3; 1-2-3, 1-2-3, 1-2-3.1512

Then we are going to look if that rotation in moving from 1-2-3 is a clockwise rotation; then we describe that chiral center as being an R configuration; clockwise meaning right-handed.1522

It is like if you turned a steering wheel clockwise, your car would make a right-hand turn; so clockwise means right-handed; that comes from the Latin Rectus.1537

If the rotation instead is counterclockwise, that is like making a left-hand turn; that configuration is known as S; and that comes from the Latin Sinister for left-handed.1547

So that is how we are going to determine R and S; let's take a look our first example.1558

Do have any chiral carbons or asymmetric carbons on this first molecule?--well, sure; right here this carbon has four different groups on there.1565

We would describe that as a chirality center; and that means we could name this as either having the R configuration or the S configuration.1575

Our first goal is to rank our groups; we have a carbon, oxygen, hydrogen, bromine; our highest priority group is the bromine, #1.1584

Next is oxygen; we could just refer to the periodic table if we need to see who has the higher atomic number.1595

Hydrogen is always going to be #4; and that means this carbon is #3; so we rank our groups 1, 2, 3, 4.1604

Now what we do is we view the molecule with the lowest priority group #4 pointing away from us.1611

If we look at this right here, we see that the hydrogen #4 already is pointing away from us because it is a dashed bond; wo we already are viewing it from the right perspective.1617

We go from 1 to 2 to 3... 1 to 2 to 3; 1-2-3-, 1-2-3, 1-2-3; keep doing that rotation; and how would you describe that rotation?1626

Looks like a counterclockwise rotation; and because it is counterclockwise, we call this the S configuration; so this is the S molecule.1640

Let's try another one; here we have another chiral carbon right here; another asymmetric carbon; and we need to identify the four groups and number them.1654

I only see three groups there; where is the fourth group?--there must be a fourth group.1666

Remember for line drawings, it is common to omit the hydrogen; because we have these two bonds in the plane and the chlorine is a wedge, there must be a hydrogen right here as a dash.1671

This is where we are really going to have a firm understanding of line drawings and three-dimensional shapes.1682

Now I see my four groups; we have a hydrogen, chlorine, carbon, carbon; so that allows me to rank chlorine as #1 and hydrogen is #4; but now we have a tie.1688

We look back at our rules; we say in the case of a tie, we are going to move away just one atom at a time until we find a difference.1702

Let's ask this: what three groups are attached to this carbon?--I know it is attached to the chiral carbon; what are the other three bonds?1709

It is just a CH3, isn't it?--so we have a hydrogen and a hydrogen and a hydrogen attached.1718

Let's come over to this carbon and ask the same question; what are the three bonds to this carbon?--well, this has a carbon and then a hydrogen and a hydrogen; so now we have broken the tie.1725

Once again we are going to look to the atomic number; which has the highest atomic number?1738

This carbon beats out the hydrogen; so this is going to be group #2 and this is going to be group #3; so ranking the groups 1, 2, 3, 4 sometimes requires a little work here.1742

Next we are going to make sure our lowest priority group is pointing away; it is doing that; it is a dashed bond.1756

What do we do?--we move from 1 to 2 to 3 and we keep doing that; 1-2-3, 1-2-3, 1-2-3; and what does it look like here?1761

Now it looks like we are doing a clockwise rotation so this is going to be the R configuration.1770

Let's see a few more examples; how about this structure?--do we have any chiral centers in this one?--we are looking for a carbon with four different groups on it.1777

Well yeah; it looks like here where we have shown some stereochemistry, this looks like a chiral carbon.1788

We have our dashed hydrogen is missing from the structure so we can add that in to make sure we see all four groups.1794

And what are the atoms of attachment?--we have a carbon, carbon, hydrogen, nitrogen.1802

The first assignment we can make is that nitrogen is #1 and hydrogen is #4; and then we have these two carbons being in a tie; so let's look at them one by one and see what is attached.1810

What do we have on this carbon?--we have an oxygen and then a carbon and a carbon.1823

And what do we have attached to this carbon?--well, now we have a double bond.1831

If we refer back to our Cahn-Ingold-Prelog rules, it says that you can treat a double bond the same as if it were two single bonds to that atom.1836

So what we have for our three bonds is we have an oxygen and another oxygen and a hydrogen.1843

What I want you to be careful of is avoiding the temptation to add these groups up and see which total is higher; we are not doing that; we are simply looking for the highest priority group.1853

They each have an oxygen so that is tie; so then we move to the next highest priority; this has a carbon and this has an oxygen; so the second oxygen wins here.1865

So this is group #2--this carbonyl group; this whole group attached to the chiral carbon is group #2.1876

And this whole group is going to be group #3; so now we have ranked our groups 1, 2, 3, 4.1882

Then what do we do?--we move from 1 to 2 to 3 and we keep doing that; make sure you keep making a complete circle and keep doing the rotation; 1-2-3, 1-2-3, 1-2-3.1890

This looks like a counterclockwise rotation; so this is the S configuration... the S configuration.1900

How about the next one?--this looks like our chiral center; that is the only chiral carbon there is.1911

We have a hydrogen here still a dash; we will look at examples where it is not a dash next; so he is group #4.1921

Now we have a three-way tie--all three of these are carbons; so let's see which one is going to win.1928

Again it might be tempting to say: wow look at this big group; this must be the #1 priority.1934

But again we are not doing that; we are going to have a systematic approach; and that means we are just simply going to move out one atom at a time and decide which one is the higher priority.1939

What does this carbon have attached to it?--what three?--there is only going to be three bonds from that carbon.1950

There are three hydrogens--hydrogen, hydrogen, hydrogen; this carbon has a carbon and then two hydrogens; this carbon has a carbon and a carbon and a hydrogen.1956

Right away just moving out one atom at a time, we've already broken the tie.1973

Who is our #1 priority?--this group up here; and then this group is #2; and then this methyl group over here is #3.1977

Now we go from 1 to 2 to 3; 1-2-3, 1-2-3, 1-2-3; we see that it is clockwise; this is the R configuration; very good.1992

How about the next one?--now we have a case where when we add in our missing hydrogen, we see that this now a wedge instead of a dash; so we need to figure out what to do in that case.2005

Let's rank our groups first; who wins?--we have a carbon, iodine, hydrogen, and chlorine.2015

Iodine has the highest atomic number so that is #1; chlorine and then carbon and then hydrogen.2022

This turns out this oxygen over here--we never were concerned with that because we didn't have a tie; so we just look at the four attached atoms.2031

Now we want to move from 1 to 2 to 3, but this hydrogen--this lowest priority group is in the wrong direction; well, let me show you something.2042

If we are holding this molecule so that the lowest priority group from you is pointing away; let's say we are going in this direction to do 1-2-3; the rotation that you see is counterclockwise.2051

Guess what rotation I see from my point of view?--I see clockwise; so you see the exact opposite.2067

So if your lowest priority group is exactly in the wrong position--the opposite position, all you need to do is reverse the rotation that you are going to do.2075

Let me show you want we are going to do; we are going to go from 1 to 2 to 3 and then we are going to back it up and go backwards; and instead we are going to go from 3 to 2 to 1.2088

#4 is a wedge so we are going to reverse our rotation; in other words, we are going to go from 3 to 2 to 1 and then look at that rotation.2100

From 3 to 2 to 1, this is a clockwise rotation; and clockwise is always the R configuration.2117

If your lowest priority group is a wedge instead of a dash, it is really just as simple to do it.2123

We just have to remember that the correct orientation--the correct point of view is one which has the lowest priority group pointing away; so that is when we are going to reverse it.2130

How about this last group?--how about this last group if we try and assign the configuration R or S?2140

Bromine is #1; hydrogen is #4 as always if you have a hydrogen; and how about the other two groups?--when we go to rank these 1, 2, 3, 4, what do you see?2148

Well this is a tie; this is a carbon and a carbon; and they are both CH2s; and then when we move out these are both CH3s; so these two groups are identical.2161

We are not going to be able to number this 1, 2, 3, 4; so what does that do to this chiral center?--does that make this R or S?2174

It is kind of a trick question, isn't it?--because these two groups are identical, that means this carbon atom in this molecule is a plane of symmetry; this is an achiral carbon; so it is not R or S.2182

The R and S configuration is only something that we consider for chiral carbons meaning a carbon with four unique groups attached to it.2200

If you ever find that you can't rank them 1, 2, 3, 4, and you have a tie, that means you are maybe looking at the wrong carbon in order to assign your R and S configuration.2207

Let's get some practice drawing stereoisomers; let's say we are asked to draw S-2-bromopentane; how could we do that?2220

We could draw pentane; one, two, three, four, five--so there is pentane.2230

On carbon 2, we have a bromine; and what we are going to need to decide--what are our two choices?2237

That bromine can either be a wedged bond or it can be a dashed bond; and only one of them is going to have the S configuration.2244

You could spend an awful lot of time thinking this through in your head and planning it out and trying it get the right answer right off the bat.2251

But that might turn out to be a pretty big waste of time; my advice is to just guess and pick one of them; let's say we want to have it as a wedge.2256

Then what can we do?--we can check to see if we made the right guess.2268

Bromine would be #1; and between these two carbons, we have a methyl and we have this propyl; this has an extra carbon attached so this is #2; this is #3; and our hydrogen is pointing back.2273

Did we make the right guess?--did we make the right guess?--no, this looks like we drew the R configuration.2287

Guess what we have to do?--all we have to do is just erase it; I'll just cross is out so I can leave my work here.2294

But I just made the wrong guess; and it is just the bromine as a dash instead; you could confirm this if you want but this would in fact be the S configuration.2302

A lot of times it is a lot faster to pick one of the stereoisomers and then confirm it rather than try and guess in your mind what is going to be the appropriate one.2314

So that would be S-2-bromopentane; now what if I asked you to draw the enantiomer of S-2-bromopentane?--we already see what the structure of the S enantiomer looks like.2325

If I wanted to draw the other enantiomer, there is two methods; there are two approaches we can take to this problem.2335

One approach is we could draw the mirror image because we know the definition of an enantiomer is that they are mirror images of each other.2342

We can imagine a mirror to the side or to the bottom and maybe we can draw it like this.2349

Draw the bromine here; this would be the mirror image of this if I had a mirror right here; or if I had a mirror right here you could see it.2356

So that should be the enantiomer; that is one possible way to do it; some students have an easier time drawing mirror images than others.2366

But there is another method we can have; what we can do is we can invert all of our chiral centers; and by invert I mean swap two groups.2376

In this case we are going to keep our carbon chain fixed; but instead of having the bromine be a dash, our bromine is going to be a wedge.2389

That is another way in fact to draw an enantiomer accurately; and so whichever method works for you, they both should result in the right answer.2401

Are these the same answer?--are these the same compound?--you see that?--well, sure.2410

If I take one and I simply flip it over, they should superimpose; if I flip over one, the bromine that was a wedge becomes a dash, and they will line up very nicely.2415

Let's check the configuration here?--we can do it on this one.2426

Here we have bromine is 1, propyl is 2, and methyl is 3; looks like this is the first guess we had up top here, isn't it?--this is 1-2-3; this is the R configuration.2429

How about this one?--if this is the same molecule as this, it should have the same configuration; let's check that.2444

This is #1, this is #2, this is #3; and I go 1-2-3, but where is my lowest priority group?2449

My lowest priority group is actually a wedge so I am going to have to reverse this and go backwards 3-2-1, 3-2-1, 3-2-1; yes, this is in fact also the R configuration.2459

Either one of these got to the right answer; and something that we can observe here is that the enantiomers have opposite configurations... they have opposite configurations.2471

If one enantiomer is the S configuration, the other enantiomer must be the R configuration; that will always be true.2492

Even if you have multiple chiral centers, all of the configurations in the chiral center is one enantiomer; it will be the opposite in the other.2499

I would like to talk about a shorthand notation we can use to draw chiral centers; these are known as Fisher projections.2510

Here is the definition of a Fisher projection; what we are going to do is we are going to view a tetrahedral carbon from a very unique perspective.2518

Usually we draw tetrahedral carbons or we view them in such a way that two bonds are in the plane so it is easier to draw.2527

One is a wedge and one is a dash; that is usually how we draw our drawings.2534

For a Fisher projection, what we are going to do is we are going to hold the chiral center or the tetrahedral carbon this way so that only the carbon atom is in the plane.2538

The two bonds on your right and left are projecting out towards you; it is like you can reach out with your right and left arms and hold on to these atoms on the side; these groups on the side.2546

The top and bottom groups are pointing away from you; they are actually dashed going back into the plane.2556

If we always view the tetrahedral carbon with this exact perspective, then we don't need to use the dashes and wedges.2562

What we do in a Fisher projection is we project the wedges back into the plane and project the dashes forward into the plane; and we draw it simply as a cross.2568

Even though this is drawn all as straight lines, none of these bonds are actually in the plane.2579

This is a very special convention; and it means that the side groups are wedges.2584

Kind of looks like a bowtie, doesn't it?--some of my students tell me that is a way to help that remember what a Fisher projection looks like.2589

These side groups are actually wedges and these top and bottom groups are dashes.2595

By convention the carbon chain is usually drawn in this vertical position; so although you can look at a tetrahedral carbon this way or this way, there is a few different points of view you can have.2601

If this was the carbon chain, usually we put that in the vertical position; we will see lots of examples of this.2616

Here is one example; let's say we are asked to draw this Fisher projection.2623

We have four carbons; we have a chlorine as a wedge here.2634

What we are going to do for the Fisher projection is instead of viewing this molecule from the side.2641

We are going to be tipping the molecule up like this so that we are viewing this tetrahedral carbon as defined by the Fisher projection.2645

As defined the carbon chain is top and bottom pointing away from you; and the two side groups, in this case chlorine and hydrogen, are projecting out toward you and are wedges.2652

In this perspective, where do you see the chlorine?--it is on your left.2664

So when we draw the Fisher projection... let's number our carbons here; let's say 1, 2, 3, 4.2670

Carbon 1--let's put this up here; we have a one-carbon chain up here.2681

Then on the bottom, we have this two-carbon chain CH2CH3; so this is 2 and this is 3 and this is 4; so I'm drawing here the backbone of the Fisher projection.2687

What we are going to see is when we view it like this so that the methyl group is up and the ethyl group is down, the chlorine should be on our left; that would be an accurate Fisher projection.2700

That is great if you have a model and you can pick it up and move it.2717

But if we don't have a model, I think another good strategy you can use is rather than taking the model and picking it up and moving it, is we can pick ourselves up and move our point of view.2722

If we were to leave this molecule in the plane as drawn, what would be the perspective that I would need to take to view this molecule so that I see this picture?2734

With the chlorine and hydrogen projecting out toward me and the methyl up top?2744

What I would need to do... how about if I laid down on the bottom here and viewed the molecule like this?2748

If I were to lay down in that position, the methyl group would be aligned with my head; the ethyl group with my feet; and looking up in this direction, where would you see the chlorine?2758

If I am in the plane, the chlorine would be a wedged bond which would be on my left; so we can have this little person saying the chlorine is on my left.2767

Using this stick figure is a nice way to maybe see it from the proper perspective.2782

Another thing you can do if you have some time to check your work is you can check the configuration.2789

If you have drawn the proper Fisher projection, you should still have the same configuration that you had on the line drawing.2793

What was the configuration of this carbon 2 here?--was it R or S?2799

We have #1 here, #2 here, #3 here, #4 here; our lowest priority group is pointing away as it should.2805

So we go from 1 to 2 to 3; 1-2-3, 1-2-3, 1-2-3; this was the R configuration; let's check to see if this is still the R configuration.2816

Same priorities; chlorine is 1, ethyl is 2, methyl is 3, hydrogen is 4; we move from 1 to 2 to 3 and now let's check our lowest priority group.2828

Where is our lowest prioirty group?--is it pointing away like it needs to be?2843

It is in this side position; what is the definition of the side position of the horizontal groups?2847

Remember that bowtie; that side position is like it is coming out towards you; you can grab it with your right and left hands; it is a wedge.2851

What do we do if our lowest priority group is a wedge?--we reverse our direction and we go 3-2-1, 3-2-1, 3-2-1.2859

Sure enough, we did draw the correct configuration here; these both have the R configuration.2866

What is very nice about being able to draw a Fisher projection is that it allows us to draw chiral centers very very quickly because we don't have to worry about dashes and wedges.2874

It also makes it super easy to draw mirror images because now we don't have to worry about dashes and wedges.2883

Nearly everyone, even the most artistically challenged or spatially challenged student, can draw the mirror image of this Fisher projection.2889

We have a hydrogen closest to the mirror; we have a chlorine further from the mirror; we have a methyl up top and we have an ethyl down below.2896

Just like that we drew the mirror image; much much easier to draw it for a Fisher projection than a line drawing.2904

I have a feeling that as you get comfortable with Fisher projections, you will very likely prefer to use them if you have a choice on how to draw your chiral centers.2910

What should the configuration of this mirror image be?--since this is a chiral molecule and we just drew its enantiomer, I think this better have the S configuration.2921

I just inverted my chiral center; look if you compare these two, we just swapped the position of the hydrogen and the chlorine.2932

Sure enough, we go from 1 to 2 to 3, but then we back it up again 3-2-1, 3-2-1, 3-2-1; this is in fact the S configuration.2939

We just drew the Fisher projection of this molecule and then drew its enantiomer very quickly.2949

One other very nice use of Fisher projections is if we have to assign the configuration where if our #4 group is in the plane of the page.2954

Let me redraw this in case it is a little too low to the bottom of the screen.2963

If we were given this molecule and we were asked to assign it as the R or S configuration, we would have a hard time doing it.2968

Because our lowest priority group is not a wedge projecting out toward you; it is not a dash pointing away from you.2976

It is in the plane which means it is parallel to the plane; and we don't have any rules for that.2983

In that case, I think one of the quickest and easiest strategies is to view this molecule as a tetrahedral carbon with this orientation so that you can convert it to a Fisher Projection.2990

What do you think?--if I do this; if I view it from this angle.3005

Here is the tetrahedral carbon as I see it; what groups do I have on the top and bottom from this perspective?3010

Looks like I have a hydrogen aligned with my head and a methyl group aligned with my feet.3017

Here is the tricky part: I have two groups on my right and left; they are both coming out toward me; and where is this OH?3024

If I am in the plane of the board, the OH is going to be on my left-hand side.3032

Very good; if you can do that with a little practice, you've got Fisher projections down; piece of cake.3038

What is nice about a Fisher projection is by definition every group is either a dash or a wedge so it is always a simple exercise to assign the configurations.3047

Now all we do is we assign our priorities; oxygen is #1; hydrogen is #4; and for these two carbons, since this one has an oxygen attached, he is a higher priority than the methyl.3055

We rank our groups 1, 2, 3, 4; we move from 1 to 2 to 3; and then we check our lowest priority group; where is it?--it is in the up position.3069

And what does that mean?--that means it is pointing away from us just like it should be; so we keep our configuration.3080

1-2-3, 1-2-3, 1-2-3, and what do we have here?--we have the R configuration.3086

This is a very simple rapid way to assign configurations if your molecule is drawn in such a way with the lowest priority group in the plane.3091

Another example where picking up your body and moving it is going to be a good strategy in getting the proper perspective.3101

Let's take a look at some molecules that have two chiral centers and see what we can do with those.3111

Here we have an example of 2-bromo-3-chloropentane; I've drawn them both here as wedges.3119

Because this molecule has two chiral centers, each of them can be described as being the R or S configuration; so I've put some parentheses out here in anticipation of that.3126

Let's complete the name of this molecule because the stereochemistry, the configuration, is going to be a part of the complete name of a molecule whose three-dimensional shape is given.3137

Here On carbon 2, we have a bromine; let's determine that configuration.3149

This is group #1; let's write them without making too big of a mess; group #2, group #3; so we go from 1 to 2 to 3; and our lowest priority group is a dashed hydrogen.3154

So we go 1-2-3, 1-2-3, 1-2-3; so at carbon 2 we have the R configuration; so we are going to call that 2R out front because we have to say which carbon we are describing.3168

Then on carbon 3, we have a chlorine; and this chlorine has group #1 and group #2 and group #3; our lowest priority group is pointing away like it should; looks like this is also the R configuration.3180

This stereoisomer that is drawn is described as (2R,3R)-2-bromo-3-chloropentane.3192

It is simply put out in the very front of the name; in parentheses is where we put all our stereochemical information.3200

How about if I wanted to draw the enantiomer of A?--we will call this molecule A; for short, the enantiomer of A.3207

Remember there are two ways we can do it; we can either draw the mirror image; 5338 As our molecules get more complex, you might imagine the mirror images are going to be a little more challenging to draw.3214

I would recommend or personally what I think would be the easiest way to draw the enantiomer is to keep my carbon chain the same.3224

So bromine is still on 2 and chlorine is still on 3; but I would invert the chiral centers; so they were both wedges; they are now going to be both dashes.3232

I automatically know that this is now the enantiomer of A.3243

Let's call this molecule B; and what do you think the configuration is going to be for B?3246

It must be the opposite now of A; so it is going to be 2S,3S; of course you can check all that later; go back; that is some very good practice that you can get.3254

How about the Fisher projection of A?--if I wanted to do the Fisher projection, now we have again our carbon chain.3266

Let's number it so we can get oriented; one, two, three, four, five carbons.3272

We have a methyl group; and then carbons 2 and 3 are both chiral centers; so our Fisher projection has now two horizontal lines.3276

In fact, Fisher projections are ideal for drawing molecules with multiple chiral centers because it is greatly simplified in this form.3284

What we have to decide then to draw an accurate Fisher projection for A is where do we locate the bromine and the chlorine?--are they going to be on the right or left on each carbon?3294

We have to get the proper perspective; and let's see if we can do that using our line drawings or stick figures.3302

For carbon 2, what would be the proper point of view to view carbon 2 so that the methyl group is pointing up and away from me?3313

And then the two groups on carbon 2, the hydrogen and the bromine, are both projecting out toward me as wedges?3320

We are going to have to come up from above the molecule looking down; and now that is exactly what we see.3327

We see our bromine and our hydrogen on carbon 2 both coming toward me; carbon 1 and carbon 3 are both pointing away from me; and where is that bromine?3335

If I am lined up in this perspective and I am in the plane, the bromine is going to be on my left... the bromine is going to be on my left.3346

On carbon 2, I am going to draw the bromine on the left and hydrogen on the right.3364

How about for the chlorine?--I can't stay up here with this same perspective and view down at the chlorine because now the chlorine isn't coming toward me.3369

It is pointing away from me; so that is the improper perspective.3377

The easiest thing for me to do is pick myself up and move myself down here and view in this direction; now I am looking at it from underneath the plane of the molecule and looking up.3382

When I do that, again carbon 1 always need to be aligned with my head; where is that chlorine?3394

If I am in the board, that chlorine is coming down to my right... the chlorine is on my right.3398

When I come up to carbon 3 here, that is what I see; and there is my Fisher projection of A.3410

We can confirm that we've done it correctly; this should still be 2R,3R; in fact it is.3416

Let me show you this molecule... seeing I think I have it built here.3422

Here we have the bromine and the chlorine as both wedges on my five-carbon chain; and let's take a look at what that Fisher projection is.3428

The Fisher projection is actually viewing the molecule like this so that the bromine and hydrogen here are coming out towards you.3435

But then this carbon also comes out towards you so what we've done is we have rotated the molecule to have this conformation for a Fisher projection.3444

In a Fisher projection, all the chiral centers have the two groups pointing out towards you; so the molecule wraps itself around like this.3455

The methyl group is at the very top; ethyl group is the very bottom; we see that the bromine is on our left and the chlorine is on our right.3463

What we did over here was instead of having the model because we didn't have the model to pick up.3470

What we did is we viewed the molecule from the top looking down over here; and that is how we saw the bromine on our left.3477

Then we came down here and we viewed the molecule like this looking up; when I do that, now I see that the chlorine is on my right.3485

A little practice with models again will really pay off here; ultimately though we need to be able to work just on paper and with these three-dimensional drawings.3494

A little practice with both gets you up to speed very quickly.3507

How about if I wanted to draw B?--again, once I have the Fisher projection of A, the Fisher projection of B is very straightforward; we just draw its mirror image.3511

Methyl at the top; methyl at the bottom; and on the top carbon, we have a hydrogen on the inside and a bromine on the outside.3522

On the next carbon, we have a chlorine on the inside and a hydrogen on the outside.3532

There it is; we just drew the mirror image of B; this must be 2S,3S; we can confirm that if we wanted to.3536

What is the relationship between A and B?--because A is chiral and because B is its mirror image, A and B are enantiomers... non-superimposable mirror images.3544

Are there any other stereoisomers that exist for 2-bromo-3-chloropentane?3563

We have one example here in this line drawing where they are both wedges; we have one where they are both dashes3569

Are there any other arrangements we can have?--well sure; we can have one as a wedge and one as a dash.3574

So here are the other possibilities we can have; we have already seen A and B where we have wedges and dashes.3582

What if we were to have one wedge and one dash?--this now would be another unique stereoisomer; let's call this molecule C.3589

Just by referencing it to the structures A and B we've already drawn, we even know the configuration.3602

The configuration matches A here so it is 2R, but then it is the opposite for the next one so it would be 3S; so we have this molecule.3608

And instead we can make the bromine the dash and chlorine the wedge; and this too would be a unique compound; this molecule we can call D; and this has 2S,3R.3623

We could draw the Fisher projections of these as well; and these would be good to practice with; in drawing these Fisher projections, you can use the stick figures or you can use models.3644

But just in comparing it to the Fisher projections we already have for A and B, we can see that for C, it is going to have the bromine and the chlorine both on the left.3658

Then for D, it is going to have the bromine and the chlorine both on the right.3672

What is the relationship then between these next two stereoisomers that we've drawn?3686

Looks like their configurations have change; we've gone from R,S, to S,R; looks like they are mirror images of each other that are non-superimposable.3692

And yes, you might guess that these are also enantiomers; so we have another pair of enantiomers; so these are all the stereoisomers of 2-bromo-3-chloropentane.3701

The question that you might be asking is then what is the relationship between A and C?3713

A and B are enantiomers of each other; A and C are clearly stereoisomers because they are both 2-bromo-3-chloropentane; they have the same connectivity; they only differ by their stereochemistry.3728

The way we describe those two structures is we call them diastereomers... they are called diastereomers.3741

Pretty much, the definition of a diastereomer is a stereoisomer that is not an enantiomer.3752

If you have two molecules that you decided are stereoisomers that are non-superimposable and they have the same connectivity, you only really have two choices.3767

They are either going to be enantiomers or diastereomers.3776

Do we have any other diastereomer pairs?--when we look at these four structures, what other compounds can be described as diastereomers of each other?3780

A and C are diastereomers, but A and D are also diastereomers; and the relationship of B to either C or D would also be a diastereomer.3792

So A and D, or B and C, or B and D; so any other combination other than the enantiomers, we describe as diastereomers.3806

In other words, all stereoisomers are either enantiomers, which we describe as non-superimposable mirror images.3817

Whether you can see that or not, they will always have that relationship.3844

Or we are going to describe them--all other possibilities are called diastereomers; they have the relationship of being diastereomers; so they are non-mirror images.3847

Another way that we can distinguish between enantiomers and diasteroemers--if you compare structures A and B, you see that all of our chiral centers have been inverted.3859

All our wedges have been turned to dashes; and for C and D, every wedge is now a dash and every dash is now a wedge.3868

Another thing we can look at for enantiomers is that all chiral centers are inverted.3875

Where for diastereomers, if you have multiple chiral centers and if you invert some but not all, then you would be diastereomers; not all chiral centers inverted; only some have been inverted.3888

Let's say you have ten chiral centers; if you invert all ten chiral centers, that structure would be the enantiomer of the original.3907

Any other combination, if you just inverted one or two or five or eight, then all those structures that you could draw would be diastereomers.3914

We will find that you can have many diastereomers but only one enantiomer; only one molecule would be the exact mirror image and with all the chiral centers being inverted.3922

It turns out the possibility for the # of stereoisomers is you could have 2n stereoisomers possible where n equals the # of stereocenters.3935

The term stereocenters can refer to chirality centers; chirality centers like chiral carbons.3955

You could have an R and S possibility; but another possibility for stereoisomerism is if you have a double bond, you can have cis and trans isomerism.3961

Maybe double bonds or rings, groups being cis or trans on a ring, cis or trans on a double bond; all those stereoisomers we can have 2n possible.3974

Because 2-bromo-3-chloropentane has two chiral centers; that is why we had four possible stereoisomers that are shown here.3984

Let's take a look at another example--how about if we wanted to draw all stereoisomers of 2-3-dichlorobutane?--now what would be a systematic way of doing that?3995

We could draw a four-carbon chain; there is butane; and we have a chlorine.4007

Let's draw them both as wedges to start off with; that would be one possible stereoisomer.4012

It turns out that this is 2R,3R; I'll let you check that on your own; and we can call this structure A.4017

We could draw it as a line drawing or we could draw it as a Fisher projection.4026

Again, I am just going to draw the Fisher projection; and you can confirm that on your own later and try it.4029

One chlorine is going to be on the left; the other is going to be on the right; this would still be A.4037

What would be another stereoisomer we could draw?--how about the enantiomer of A?4045

We could draw the mirror image of A either as the Fisher projection... either as the Fisher projection; this is now a unique compound; we will call it B.4050

Or as the line drawing; the line drawing would have instead of both chlorines as wedges, it would have both chlorines as dashes.4069

This would be 2S,3S; and that would be structure B; that would be the enantiomer.4081

This is a pretty systematic approach; we could draw both as wedges and then both as dashes.4090

What would be another possibility?--well, we could draw one as a wedge and the other as a dash; so this is a clearly unique compound; we would call this 2R,3S.4096

Our top carbon here stayed the same and the chlorine on the left; but now the bottom carbon moved the chlorine over to be on the right; so this is structure C.4114

Now we could draw its mirror image; so it is useful to draw stereoisomers as pairs of enantiomers; pairs of mirror images with inverted chiral centers.4127

Hydrogens on the inside; chlorines on the outside; and that would be the same structure; but instead of a wedge and then a dash, we could have a dash and then a wedge; and we would call this structure D.4137

But there is a problem with this analysis; there is a problem here.4155

I want you to compare these two Fisher projections or even these two line drawings; are these in fact unique structure?4159

Can we take this line drawing and just rotate it in the plane and turn it over like this and have it aligned with this first structure?4171

The same thing with this Fisher projection; I could take one Fisher projection and just rotate it 180 degrees to line up with the other?4182

You can in fact do this; so what we are observing is that this molecule is not a unique compound; these two are superimposable.4190

These are not structures D as you might have guessed; even though we drew the mirror image, we still drew the same molecule; we had a repeat of a structure we had already drawn.4204

What is going on here?--why do we not have four possible stereoisomers here?--well, let's take a look closer at this structure C.4218

Again, I've just redrawn; we have it as the line drawing that are superimposable or the Fisher projections that are superimposable.4226

What is happening--the reason our images are superimposable and identical is because we have a plane of symmetry in C.4233

Anytime you have a symmetrical molecule, remember the mirror image is identical as to the original structure.4245

What we have is a very special case here where the carbon has a plane of symmetry which reflects one chiral center onto another.4253

That is a very special kind of symmetrical molecule; it is called a meso compound.4260

In other words, it does have chiral centers; it does have two chiral centers; we can name those as R or S.4268

But the molecule as a whole has a plane of symmetry that reflects one chiral center onto the other chiral center; and for those unique compounds, we call them meso compounds.4275

Because it has a plane of symmetry, C is achiral; it is no longer chiral if it has a plane of symmetry.4288

If it is achiral, C does not have an enantiomer; of course, it has a mirror image; everything has a mirror image.4299

But what makes it not its enantiomer is the fact that the mirror image is superimposable; it is identical with the original structure.4313

In this case what we see is that there are only three stereoisomers possible for 2,3-dichlorobutane.4321

There are not 2n as we just said that we can have as a maximum; 2n represents a maximum number; what we said is actually there is 2n that are possible.4330

But in a case of a molecule that is symmetrically substituted, any three-dimensional arrangement that gives symmetry from one half to the other through an internal plane of symmetry.4345

It means that we are no longer going to have them occurring in pairs because that symmetrical molecule is not going to have an enantiomer.4358

If we take a look at this molecule, here we have 2,3-dichlorobutane; we have a chlorine as a wedge and a chlorine as a dash.4367

This looks like an asymmetric molecule; but if we rotate this around so that we try and make it symmetrical.4380

In fact, remember that is what the Fisher projection does for us--is that it makes it a symmetrical molecule.4390

We see that in fact this can be cut in half; the top half reflects on the bottom half.4397

What we can do here is we can even see this in the line drawing if we rotate this about this single carbon-carbon bond.4403

If we were to look at this molecule in this conformation it would be a little easier to see how in fact that it is a symmetrical molecule and it would not have an enantiomer.4413

If I drew these both as wedges or I drew these both as dashes, it would be the same molecule; I just flipped it over.4424

If I draw them both as wedges, it is the same exact molecule as if I draw them both as dashes.4430

Keep in mind when you are looking for symmetry, when you are looking to determine if something is chiral or achiral.4435

Make sure you rotate it around and get in it in the most symmetrical conformation possible so that you don't miss any potential planes of symmetry.4440

One more thing that we should talk about that is important for stereochemistry is the concept of optical activity.4453

This is one of the physical properties that we can discuss for stereoisomers.4460

What is known is that chiral molecules... so again, molecules that do not have an internal plane of symmetry.4467

Chiral molecules rotate a plane and polarize light; for that reason, chiral molecules are called optically active.4473

They are described as being optically active because they rotate a plane of polarized light.4486

This angle of rotation called alpha (α); the angle that it rotates is measured by an instrument called a polarimeter.4492

Let's see what it means to be polarized light and how that plane might be rotated.4498

This is kind of a cartoon of what polarized light looks like; imagine if you were looking directly at a beam of light; let's see what ordinary light looks like.4504

Ordinary light if you are looking straight at it... light oscillates; so if you are looking straight at it, it is going to be coming as a wave toward you.4516

You are going to see it oscillating; but it is going to be going in every direction; so ordinary light has oscillating waves of radiation going in every direction.4526

What a polarimeter does is it filters that out so that all you see is a single plane of oscillation of the electromagnetic field; so you can show it like this.4541

If you take this polarized light and you pass it through a chiral object--a chiral sample, that plane is going to rotate; and it is going to rotate one way or the other.4552

If it rotates in this direction, we describe that as having a positive angle; so maybe a +10 degrees or 20 degrees or 90 degrees.4563

We describe those molecules as being dextrorotatory; they have a right-handed clockwise rotation.4573

If the molecule rotates in the opposite direction, we describe that angle as being a negative angle; and we describe those molecules as being levorotatory.4581

We use the little l or d to describe these molecules; and that is how we describe it when we see a counterclockwise rotation.4591

Chiral molecules are going to optically active; and we can measure their α.4603

An achiral species, something that is not chiral, are not optically active.4607

In other words, if you put them in a polarimeter and you pass a beam of polarized light through it, that beam is going to pass through unchanged.4612

In other words, α= 0 degrees for an optically inactive species such as something that is achiral.4620

What are some other physical properties of stereoisomers that we can take a look at?4633

It turns out that if we are comparing enantiomers and the relationship of enantiomers, we will see that they have identical physical property.4642

Every physical property that you want to measure--things like its boiling point or melting point or solubility or its NMR or its IR spectra; those sorts of things.4649

They are going to be exactly the same; they will be completely indistinguishable except for this optical activity; it turns out they have equal and opposite optical rotation.4657

If one enantiomer rotates it clockwise, the other enantiomer is going to rotate it counterclockwise; one will have a + angle and the other will have a ? angle of the exact same magnitude.4669

When we are comparing diastereomers, stereoisomers that that are not enantiomeric and that are not mirror images of each other, they just have different physical properties.4682

Again, anything you can imagine--boiling point, melting point, their optical rotations, their NMR, their solubilities; everything you can imagine.4690

They may be coincidentally be similar, but they are not going to be identical.4702

Let's take a look at some examples; here we have some sugar molecules.4707

Sugar molecules are definitely well suited for these Fisher projections because sugar molecules often have multiple chiral centers.4712

We can draw them very easily showing the configuration about each of these polyalcohols.4720

Here is an example of ribose; and this is the 2R,3R,4R version of ribose.4730

Over here, it looks like we've drawn the mirror image; so this is the enantiomer of ribose.4737

It is still called ribose because it is the same molecule; exact same connectivity; it is just the mirror image; so this will be 2S,3S,4S.4744

In short, we could just call this (+)-ribose; sometimes this is called the specific rotation.4752

Once we measure the α angle in the polarimeter and we adjusted for the concentration and the path length and that sort of thing.4773

We report it in something that looks like this; we call it the specific rotation.4781

This shows it was the D line of a sodium light that was used; it was 20 degrees; so this is what it looks like when you report it.4788

What is found is that (?)-ribose, the 2R,3R,4R, has an optical rotation of -19 degrees; so it rotates the plane of polarized light in a counterclockwise direction for 19 degrees.4796

The other enantiomer is also going to rotate at 19 degrees, but it is going to go in the other direction; it is going to go in a clockwise direction.4812

Sometimes, we refer to the different enantiomers as the (+) enantiomer or the (-) enantiomer and that will be a way to distinguish between the two.4820

Every other physical property that you can imagine--melting point, solubility, spectroscopy--are going to be exactly the same.4831

For example, the melting point here for both enantiomers is 88 degrees.4838

Let's compare that too; so here we have two molecules which are enantiomers of one another.4843

Every stereocenter has been inverted and we now have its mirror image.4852

If we compare this structure to the next structure, you see that one of the chiral centers has been inverted but the others haven't.4856

Now we are comparing molecules that are diastereomers of each other; if they are no longer enantiomers, they are diastereomers.4864

This is a different sugar; this is called arabinose; this is the (-)-arabinose.4874

What would we predict its rotation to be?--that is not something we can predict; we can't predict it; we have to take the measurement.4881

We have to put it in a polarimeter and measure the optical rotation; there is no way to predict it; we can't say that if it is an R, it goes one way; or if it is an S, it goes another way.4897

The only way we can ever predict an optical rotation is if we know the optical rotation of one enantiomer; then we know the optical rotation of the other enantiomer. 8156 Otherwise, it is just something we have to measure.4907

Here it is a very similar molecule; and this rotation for arabinose has 104 degree rotation; and this enantiomer has it in the levorotatory direction; so -104.4919

What is a melting point?--well, again, not something we can predict; we would have to measure that.4931

You might think, well gee, they have the exact same functional group so I would expect them to be pretty similar.4937

But there is actually quite a big difference; instead of 88 degrees, we have a melting point of 162; it is almost twice the melting point.4942

The difference there reflects this stereochemical shape of the sugar; because remember the temperature of a melting point has to do with how tightly the crystals pack together.4948

The arabinose molecules because of their 3D shape must have a better packing in their crystal structure; and that is what account for their higher melting point.4965

No way we would be able to predict that; but it is just a nice illustration on how the physical properties between diastereomers are totally different, but between enantiomers they are the same.4973

So when do enantiomers behave differently?--it is possible for two enantiomers to behave differently; and that is going to be when they interact with other chiral objects; another chiral thing.4988

For example, if we take our favorite pair of enantiomers, our right and left hand, when do they behave differently?5000

If you try to pick up a water bottle or a coffee mug, something that is a symmetrical object.5007

You would be able to do it equally effectively with your right hand or your left hand in terms of how it fits with the coffee mug.5015

In this case, we would find that there is no difference on how they fit.5025

But what if I had my right and my left hand, and I had a right-handed glove that I was trying to interact with.5033

Of course my right hand would fit perfectly into my right-handed glove, but my left hand would not fit at all.5039

In this case, we observe a difference between the two enantiomers; so why is that?--what is the difference?5047

Why is one going to be indistinguishable and the other going to find a difference?--well, that is because a coffee mug is a symmetrical thing; it is achiral.5057

Because it is symmetrical, my right hand and left hand are going to see the same thing when they try and interact and dock with that mug if you will.5068

But a right-handed glove is something that is chiral; and so when you bring in a chiral molecule with another chiral molecule, they are going to interact differently.5077

That is exactly an example of that.5087

We just saw that the two enantiomers are going to interact differently with polarized light, right?5090

There is a difference there; one is going to be dextrorotatory, and one is going to be levorotatory.5097

What does that tell us about polarized light?--it tells use polarized light must be chiral in order for there to be a difference; and it is.5104

It is because it's a helix; it is actually helical, and you can have a right-handed helix or a left-handed helix; there is chirality to it.5113

That is why a polarimeter is able to distinguish between enantiomers.5120

Let me show you one other interesting example; here is another enantiomer pair; this molecule is called carvone.5125

You could call this S-carvone and R-carvone because there is a single chiral center there.5132

That would be some nice practice to confirm that you can come up with S and R.5137

Or you could call this (+)-carvone and (-)-carvone; because that is their optical rotation; you could see that they are equal and opposite.5141

But there is something else that is very interesting about carvone.5150

S-carvone, the dextrorotatory enantiomer, tastes and smells like caraway seeds; those are the little bitter seeds that you have in rye bread.5152

While R-carvone tastes and smells like spearmint; that is the minty flavor you might have in chewing gum or something like that.5165

Exact same molecule, exact same three-dimensional shape; we simply have this mirror image relationship; but a huge difference in how we perceive it in our bodies in terms of its taste and its odor.5174

What does that tell you about the receptors that must be in our noses and in our mouths?--they must be chiral.5186

Our odor receptors and our taste receptors must be chiral in that they can distinguish between enantiomers.5194

If we have an odor receptor here, one enantiomer is going to fit differently than another enantiomer; and that is going to send different signals to our brain.5202

We are going to interpret that differently as a different odor or a different smell.5209

The whole world of stereochemistry suddenly takes on a whole new light of importance.5213

Because when you think about naturally-occurring compounds, things like amino acids or sugars or enzymes, these are all chiral molecules; they exist in nature typically as just a single enantiomer.5217

When we look at biochemistry, the field of organic chemistry in living systems, we will find that stereochemistry is hugely important and those stereocenters give rise to a particular behavior.5232

In fact, the other thing to keep in mind is that drugs that we take, pharmeceuticals, are often chiral; so many of them are chiral molecules.5248

For example, ibuprofen the pain reliever is a chiral molecule; and we will talk about how that is sold in just a minute.5258

Thalidomide is a chiral molecule; and it was discovered years ago that one enantiomer was something that had very good benefits.5268

But the other enantiomer was something that had devastating effects; it was teratogenic and caused birth defects.5278

So hugely important to consider the stereochemistries of your molecules when you are dealing with things that are going to be entering the body, especially like pharmaceuticals.5286

Because the different enantiomers might behave differently.5294

Let's talk about something called racemic mixtures; that by definition is what we call it when we have an exactly 1:1 mixture of enantiomers.5302

If we had equal amounts of two enantiomers combined into a single mixture, this is now something that is going to be optically inactive; in other words, the α is going to be zero.5310

Think about it; if you have a certain amount of levorotatory enantiomer and you have that exact same amount of the dextrorotatory enantiomer, those are going to cancel each other out.5321

A net result is going to have no rotation whatsoever; so these are optically inactive.5333

In fact, most of the chiral drugs that are in the market such as ibuprofen, those are sold as racemic mixtures.5340

You have both the (+) and the (-) enantiomer in the tablet that you are taking; and again that has very important ramifications for the pharmaceutical industry.5349

Perhaps just a single one of the enantiomers is stronger acting or will last longer.5358

Maybe the other enantiomer is responsible for some side effect or that sort of thing--causing nausea or upsetting your stomach or what have you.5365

Because many of them are sold as racemic mixtures, a lot of research is going into, well, what if we had just a single enantiomer?--would that be more potent?--would it be longer lasting?5379

Do we need a different patent for that?--all sorts of interesting ramifications go on for that.5387

As you might imagine if I had a racemic mixture of ibuprofen and I wanted to separate that mixture into the two different enantiomers.5393

That is going to be quite a challenge since enantiomers have identical physical properties.5401

I can't just do a distillation; I can't do a crystallization; I can't separate them the ways that I would normally separate organic compounds because they behave so similarly.5407

There is a process though that exists that can be used; and this is used very often in the pharmaceutical industry; it is called a resolution--the process for separating enantiomers.5420

Let me just show you how in general that process would work.5430

Let's assume that we have a racemic mixture here; so this is represented by an equal mixture of (+) enantiomers and (-) enantiomers.5434

What we are going to do is we are going to take that racemate or racemic mixture, and we are going to treat it with some kind of chiral resolving agent.5443

This has just a (+) rotation or a (-) rotation; it is some chiral agent that we can get from nature or that is commercially available.5452

We are going to react it with the racemate and form some kind of interaction that is temporary; that is reversible.5463

We are going to have our (+) resolving agent now associated with both our (+) and our (-) racemate components.5471

When we compare the resulting structures, we see that these are in fact now diastereomers.5482

When you compare a structure that has a (+/+) to a structure that has a (+/-), those are no longer enantiomers.5491

They can't be mirror images; one part of the molecule is the same configuration; the other part of it is the opposite; that is our definition of diastereomers.5500

Because they are diastereomers, they have different physical properties; and if they have different physical properties, now we can separate them.5508

We can do something like recrystallize them or do a chromatography; something like that; recrystallization is a very common method here.5521

We can effectively separate the (+/+) diastereomers from the (+/-) diastereomers.5535

Then all we have to do is we can remove and hopefully recover, so we can reuse it, our chiral resolving agent; thus freeing up our enantiomers; and now we have these in two separate containers.5541

We have a container of just our (+) enantiomer and a container of our (-) enantiomer; and we've effectively separated the two enantiomers; this process is called a resolution of a racemic mixture.5561

A racemic mixture is what we call it when we have an exactly 1:1 mixture of two enantiomers.5577

But it is also possible to have unequal mixtures of enantiomers; those mixtures are described by what is known as an enantiomeric excess or ee for short.5582

This is a measure of optical purity; it is another way we can describe it; how pure is it in terms of being just a single enantiomer?5594

ee is defined by comparing the measured optical rotation and dividing that by the pure optical rotation.5607

When we take that and convert it to a percentage, that # is what we describe as the ee, the enantiomeric excess.5615

Another way to describe ee is to say that the ee is the difference between the percentage of the major enantiomer and the percentage of the minor enantiomer.5622

For example, if you had a 100% ee, 100% enantiomeric excess means you have pure enantiomer; 100% in excess of a single enantiomer; your ee is 100% of one minus 0% of the other.5633

A 0% ee means you have no excess of either enantiomer so that means you have exactly 1:1; you have a racemate or a racemic mixture.5649

In other words, 50% of one enantiomer and 50% of the other enantiomer gives you an ee of 0.5661

So 100% means I have pure enantiomer; 0% means I have exactly 1:1 mixture; and any ee percentage in between there means I have some kind of mixture of the two enantiomers.5668

et's take a look at some examples; here we have an alcohol that is the S-alcohol.5681

It is known that this pure S-alcohol has an optical rotation of +20 degrees.5691

Just like other physical properties like melting point or boiling point, this is something that can be measured; support in the literature; and you can look that up.5698

Do we know what the pure R enantiomer would have as an optical rotation or as a specific rotation?5709

If we had a pure R with none of the S in it, we would expect that it would have the same magnitude but the opposite sign; so it would be -20 degrees.5714

What if we had the racemic alcohol?--in other words, an equal mixture of the S-alcohol where this is a dash and the R-alcohol where this is a wedge.5727

We could describe that as a (+/-); this is a way to abbreviate a racemic mixture; what would the optical rotation be there?5736

If we had exactly equal amounts, we would expect it to be optically inactive; it would be a 0 degree rotation; that is what we expect for our racemic mixture.5743

What if we had any other mixture of the R and S enantiomer; any other combination of those, where would you expect the α optical rotations to be?5756

We would expect that they would be somewhere between -20 degrees and +20 degrees; so the -20 and the +20 are the extreme rotations you can have if you had pure R or pure S.5768

The presence of the other enantiomer is going to lower that optical purity and reduce that rotation and bring it closer to 0.5787

For example--if you had a sample of this alcohol; it was pure alcohol; you took an NMR and you saw no other piece in here so it is not contaminated with any other molecule.5799

But its optical rotation is +10 degrees; then what is the ee for this sample?5808

Remember ee is defined as the observed optical rotation divided by the pure or the literature optical rotation; so we see that our sample has a +10 degrees.5817

And the pure--because this is a (+), that means I have an excess of which enantiomer?--what do I have more of?5838

I must have more of the one with the (+) rotation; so I have an excess of S.5847

But there is some R mixed in there; that is why our optical rotation isn't the maximum that it should be.5856

So I have +10 divided by +20; that means that I have a 50%; we are multiplying it by 100% to convert it to a percentage; we have a 50% ee for this sample; a 50% ee.5861

What does that mean for the percentage breakdown? How much of each molecule do we have?5879

Remember that the other way to describe ee is the major percent minus the minor percent.5884

We could do a simple algebra problem to solve this so that it comes out x; we could set the major percent as x and the minor percent would be 100-x.5893

We could do this and solve for x; and what we would find is that we have 75% of the (+) enantiomer and 25% of the (-) enantiomer.5908

Again, 75 minus 25 would come up to 50%; so you can see we have a 50% excess of the (+) enantiomer.5923

You can imagine that of this 75%, we have 50% that is our excess and 25% is going to combine with this 25% to be racemic.5937

It is like half of our mixture is a racemic mixture with (+) and (-), 25% of each; the other half of the mix is pure (+); so that is why our optical rotation is only half of what we are expecting.5951

Let's say we have a 100g sample, only 50% of it is the pure (+) that is going to be giving the optical rotation; the other 50% of it is a racemic mixture that has no optical rotation.5968

I just want to give you a feel for how to work with the ee's.5979

One more example; what is the percent composition of a sample with 90% ee?5987

Again, that means we have 90% of one enantiomer plus 10% of the racemic.5992

We have 5% and 5%; so that means we have 95% of one enantiomer plus 5% of the other enantiomer.6003

This is just one way to think about it again; you could solve it algebraically like this to set one to be x and one to be 100-x; and then the difference now would be 90%.6016

But the difference between 95% and 5% is 90% ee; so 90% ee equals 95% minus 5%.6027

If you have a 95:5 mixture of two enantiomers, it would be described as having a 90% ee.6039

You would expect the optical rotation to be 90% of the maximum or the literature value for that sample.6048