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Dr. Laurie Starkey

Dr. Laurie Starkey

Mass Spectrometry

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 (26)

1 answer

Last reply by: Professor Starkey
Thu Aug 4, 2016 4:37 PM

Post by Adel Althaqafy on August 3, 2016

Hi Dr
thank you for explain mass spectroscopy and do you have any articles that by PDF to read it or something is short like summarize about mass spectroscopy
many thanks  

1 answer

Last reply by: Professor Starkey
Sun Oct 18, 2015 11:04 AM

Post by Jinhai Zhang on October 17, 2015

Prof. Starkey:
I have a question about the McLafferty mechanism should I use the double-headed arrow or single-headed arrow, because I google this, the web gives me a single headed arrow instead of double headed, and the mechanism is a little bit different from yours?

1 answer

Last reply by: Professor Starkey
Wed Sep 16, 2015 12:16 AM

Post by Tamrat Regasa on September 15, 2015

how can i sketch mass spectrum for 2 phenyl butane?

1 answer

Last reply by: Professor Starkey
Mon Jan 5, 2015 11:45 PM

Post by Rene Whitaker on January 5, 2015

I am still not understanding how you determine the M+ peak in chloroethane (at 20:52) and bromobutane, other than you know the compound you are looking at and so know at about what amu you should be looking at.  For example, at 20:52, if you did not know the compound was chloroethane, how would you know the peak labeled at M+ is not the base peak (since it is at 100% relative abundance)?

1 answer

Last reply by: Professor Starkey
Sun Oct 26, 2014 12:53 AM

Post by Datevig Daghlian on October 24, 2014

Professor Starkey,

  Thank you very much for your lectures! I am currently a high school student and have taken AP Chemistry and am very interested in O. Chemistry. Would you recommend I watch your lectures on O. Chemistry or should I hold off till I get to University Chemistry? Thank you!

George D.  

3 answers

Last reply by: Professor Starkey
Thu Sep 11, 2014 10:07 AM

Post by Brandon West on September 9, 2014

Do you have a systematic way of doing mass spec like you have for HNMR and IR. I really like the systematic approach you have for HNMR. In my organic class my professor will give me all 3(HNMR or c13NMR, IR, and mass spec) and I will use all three to determine the structure.

1 answer

Last reply by: Professor Starkey
Thu Jul 17, 2014 4:17 PM

Post by Kim Tran on July 17, 2014

Professor Starkey, is there anyway I can open the lecture slides in powerpoint? Thank you

1 answer

Last reply by: Professor Starkey
Tue Mar 18, 2014 12:15 AM

Post by saima khwaja on March 17, 2014

Professor Starkey,

Do you do any lectures on Organometallic Compounds?

1 answer

Last reply by: Professor Starkey
Thu Feb 13, 2014 12:17 AM

Post by Jude Nawlo on February 12, 2014

Going back to the mass spectra of aromatic compounds section: If we see 91 amu on the MS, then do we assume that our compound has the "base" with the double bond on the CH2 or does it not matter, considering the benzylic resonance forms coexist? Awesome lecture, thank you again!

1 answer

Last reply by: Professor Starkey
Fri Jan 24, 2014 10:45 AM

Post by Udoka Ofoedu on January 24, 2014

You are the best . Thank God he brought me here

1 answer

Last reply by: Professor Starkey
Fri Oct 25, 2013 10:05 PM

Post by Saif Al-Wahaibi on October 25, 2013

For the McLafferty problem, where would the positive charge be in C4H8O so that it would be observed in the mass spectrometer?

1 answer

Last reply by: Professor Starkey
Wed Sep 11, 2013 11:05 AM

Post by Ramin Sadat on September 10, 2013

Thank you for the Mass Spectrometry lecture. I have been waiting for this! Very Helpful!

Mass Spectrometry

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.

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

    Transcription: Mass Spectrometry

    Hi; welcome back to Educator.0000

    Today, we are going to talk about another spectroscopy analytical tool that is called mass spectrometry.0001

    Now, mass spectrometry does not involve the absorption of light, like we had in infrared (IR) spectroscopy; in NMR, we had the absorption of energy from radio frequencies.0007

    Because it is not an absorption of light, we don't call it a spectroscopy, even though that word is used a lot; the correct term is mass spectrometry--a slight difference in the word there.0021

    We usually call it "mass spec" for short.0034

    And, as the name implies, it has something to do with the mass of a molecule; so what we can use mass spec to learn about the structure of a molecule is: we can determine its molecular mass.0038

    That is a great analytical tool: let's say you have isolated an unknown compound from a natural product, and you want to characterize--you want to learn something about it.0050

    One thing you could do is find out how much it weighs--what is its molecular mass?0060

    And, if you have a high-resolution mass spec--if you can find out very, very precisely what its molecular mass is--you can actually learn what its molecular formula is.0064

    Instead of doing an elemental analysis to determine its molecular formula, we can learn that information from the mass spec.0075

    In addition, it tells us some structural information; we are going to maybe figure out how the molecule is put together when we look at the mass spectrum of that molecule.0081

    There is not quite as much structural information as we might get from the proton NMR, where it tells you exactly which carbons are connected to which carbons, and so on; but when we use all of these spectroscopic techniques in conjunction with each other, all looking at every single avenue for a given unknown compound, that is when they can kind of feed into each other and build on each other, and we come up with a precise structure.0094

    Another very useful tool is to use this in conjunction with gas chromatography--GC is something we use to separate a mixture of compounds.0123

    So, if you can shoot an unknown mixture into a GC and have them spread out (like column chromatography) into their different components, and then, at the end, instead of just having a detector that says, "Oh, something came out; there is an organic molecule coming out," and indicating the presence of that, if it feeds into a mass spectrometer, then not only do you know that a component has exited the column, but then you take a mass spec of that component and find out what its molecular weight is, and again, something about its structural information.0133

    So, this is an extremely powerful analytical tool; it is called GC-MS for gas chromatography and mass spectrometry together; and that is just very routinely used in the analysis of mixtures.0164

    How does mass spectrometry work--how do you go about achieving a mass spectrum?0180

    First of all, let's assume we have a neutral molecule, just represented by these little shapes here; and we have this sample: we are going to inject it into the GC, and it is going to be vaporized.0186

    The first thing we do is: we heat it up and turn it into a gas.0197

    OK, then it is going to be blasted with a beam of electrons, and it is going to ionize it.0200

    This is known as EI, electron ionization; and what happens when you hit a molecule with a beam of electrons: it causes an electron to be ejected from the compound.0210

    An electron is going to be ejected from each molecule, so now, we have an unpaired electron; so it's going to be, now, a radical.0228

    So remember, electrons come in pairs: they are either bonded pairs, or they are non-bonded pairs; they are either lone pairs, or they are part of a double bond or a single bond or a triple bond...0237

    Electrons always come in pairs; so if you remove an electron from a neutral molecule, you now have a radical somewhere--an unpaired electron.0246

    Furthermore, you have a positive charge, because that electron you removed had a negative charge.0253

    So, if it started out neutral, the molecule now has a positive charge.0257

    What we get are radical cations: radical cations are the species that are formed in mass spectrometry.0262

    And this molecule is still intact--it is still a complete molecule--and there is essentially no change in mass.0270

    Remember, an electron has an insignificant mass compared to the neutrons and the protons in the molecule.0279

    So, although we have imparted a charge on the molecule, or caused a charge to form, we have not changed the mass.0284

    And so, we will analyze this to get the mass of the parent; but then, what happens is: this is a very high-energy environment, and so fragmentation occurs.0293

    What happens is: these molecules break apart, one way or another, to split up into radicals and cations.0306

    We are going to get some fragments that are cations, and some fragments that are radicals; we are going to get a mixture, then, of both charged and uncharged particles.0314

    OK, then this passes through a magnetic field and causes a deflection of the charged compound (the uncharged compounds don't bend, and continue on to the detector, but the charged compounds do).0323

    And it separates them based on their mass-to-charge ratio; so we call that the m/z; that is read as "mass-to-charge."0339

    Usually, the charge is +1...almost always, the charge is +1; so, essentially, what we are doing is: by bending it through this magnetic field, we are separating the fragments by their masses.0350

    They are starting out all together; they break apart, and then they spread out, and they get separated by their mass.0364

    We have these various charged particles now, as a result, and the lower-mass fragment is going to travel at a faster rate than the higher-mass fragment.0372

    And this one that is the complete molecule, intact, that has not undergone any fragmentation--we describe this as M+; that is called the molecular ion, because it is the complete molecule that has just been ionized by removing an electron.0382

    That is called the molecular ion.0401

    Let's take a look at an example of a mass spectrum; this is what a mass spectrum looks like.0405

    Down on the x-axis, we have our mass-to-charge ratio; so again, remember, our charge is usually +1, so that is, we are showing the various masses of the different fragments.0412

    And over on the y-axis, we have the relative intensity: this is the abundance.0424

    So, what we are seeing here is a histogram: how many of each mass was recorded--was formed in the mass spec and then recorded in the spectrum?0430

    These various charged fragments (remember, everything we see in a mass spec represents a charged ion, a +1)--these are going to hit the detector; it records the frequency of each mass, and therefore, the taller the peak, the larger the signal; that means it is a more abundant fragment.0442

    OK, so we look at this, and we see lots of peaks here, little peaks, little, tiny, tiny peaks, even; and here is our biggest peak.0462

    The biggest peak we set to a value of 100; so this is a relative intensity--it is compared to the fragment that you have the most of; and we describe that as the base peak.0469

    So, the base peak is the tallest peak in the mass spec; it is defined as 100%, and it sets the scale for everything else.0482

    Everything else is relative: this has about a 30%, compared to the base peak, and so on.0490

    Now, why do we have a lot of this fragment?0496

    Now, the way you read a mass spec is: you can literally just count over from these labeled hash marks--count over to see what number, what mass, we have.0500

    Here is 40, so this is 41, 42, 43; so this is a mass-to-charge of 43, and that is our base peak.0510

    Why do we have so much of that fragment--why did that occur so much?--it must be a very stable fragment.0521

    If this is a stable fragment--a stable cation or a radical cation--then, if it's very stable, then it is more likely to be formed, and it is going to be showing up in a higher abundance.0530

    What we do is: we look over wherever we see the highest mass; that is typically our molecular ion, so we call that the M+.0545

    And I say it's almost always the highest mass, because sometimes our molecules are so huge or so unstable that, as soon as they ionize, they fragment right away, and you never see...none of the full molecular ion makes its way to the detector.0555

    So, it's possible that no molecular ion is evident, but...well, it depends on what you are studying, but typically, in the problems we are working on, you will see a molecular ion, and it's going to be the highest one.0570

    So here, we have the molecular ion; it is at mass-to-charge of 100 in this case; and that is the mass, given in atomic mass units.0583

    That is how we would find out, looking at the mass spectrum of this compound--we would say, "Oh, we know it has a molecular mass of 100 there."0594

    A few other things we want to point out: the mass-to-charge of 43, our most stable fragment--if you compare that to the molecular ion of 100, you see that, if we have only 43 mass units remaining, that means it broke off a fragment that was the difference of 57.0605

    So, another way that you can describe this is: you can call this M-57.0626

    There are 43 mass units remaining, and we know that a break occurred in the molecule to remove 57 mass units from it; so there a couple ways that you can describe a peak that way.0632

    And, kind of like IR, which had a lot of peaks--a lot of stretches throughout the spectrum--we don't try and analyze every peak; we just pick out the major ones.0648

    OK, and the same is going to be true for mass spec: you are going to see lots and lots of fragments; molecules can just break apart in all sorts of ways; but we are going to look for significant peaks.0658

    And typically, when you are given a mass spec, you will be asked to discuss certain peaks, and that is what we'll be doing today.0667

    Now, this is interesting: we have our molecular ion here at 100, but if you look very, very carefully (this arrow is off a little bit--sorry), you will see that we have a second little peak--very tiny--at 101.0676

    We would describe that peak as M+1, because it has 1 atomic mass unit higher than the parent.0695

    Why is that--what would cause a molecule...now remember, this is what is interesting about mass spec: we are recording the mass of single molecules and single fragments.0705

    So, if we are looking one molecule at a time, what would cause a molecule that has a mass of 100 to sometimes weigh 101--to sometimes have 101 grams per mole, or something like that, when we are looking at the molecular mass?0715

    Well, let's think about a single molecule and consider how we calculate the mass, or how we determine the mass.0735

    OK, so if we have methane (CH4), the mass of that will be the mass of a carbon atom (and that is 12) and the mass of four hydrogens (those are 1 each--4 times 1); so we are going to get 16.0742

    AMU are the units we are dealing with--atomic mass units.0760

    We would expect, if we ran a mass spec on methane, to find our molecular ion, our M+, peak at 16.0763

    OK, but remember, we have some carbons that are not C-12, but instead C-13; so what does it mean to be an isotope?--it means that you have a different number of neutrons in your molecule.0772

    So, carbon-12 has 6 protons (that is what makes it carbon) and 6 neutrons: we add those together, and that is how we get 12.0785

    But about 1% (so not many, but about 1%) of carbon atoms exist as C-13; so they have an extra neutron.0794

    When that 1 molecule out of every 100--when that one molecule comes through the mass spec, we are going to see that the carbon does not weigh 12; it weighs 13; plus, we have our four hydrogens; and it's going to be 17 amu's.0804

    And so, that is the molecule that is going to give rise to this M+1 peak.0820

    And because C-13 occurs about 1%, at 1 out of every 100 carbon atoms, this M+1 peak is going to be only about 1% of the relative intensity of the M+ peak.0828

    And that is pretty small, because our molecular ion peak is usually not a very large peak, because fragmentation usually occurs quite readily.0845

    So, it's usually a small peak; so we are looking at 1%, so it might be very, very small.0855

    OK, but what if we had two carbons?--let's think about: what would the molecular ion look like for ethane, C2H6?0861

    OK, well, now we have CH3, CH3; if we kind of have a bag full of ethane molecules, and we pull one out, one of them might have...most of them are going to have both of these as C-12; so let's say, for every 100 of these molecules, we are going to have one where there is a C-13 on the first molecule--on the first carbon atom.0869

    And we are going to have about 1% of them that will have a C-13 on the second carbon atom--so approximately 1 for each of those...it would more precisely be 1 for every 200; we would get one of these and one of these.0904

    OK, so what that tells us, though: if we have two carbons, then our M+1 is about 2% of the M+, and so on.0920

    So actually, this is something that someone who is really studying mass spec and knows it very well--that person is going to look at the size of that M+1 peak, and that is going to tell us something about how many carbons there are in that molecular ion.0936

    That is a little bit of an analytical tool we can have.0953

    Sometimes, it can be big; if it's a very large molecule, that M+1 peak might be significant, because we have really increase...let's say you have 30 carbons: you have really increased the chances, the likelihood, that one of those carbons is going to be a C-13.0956

    And every time we have one of those molecules, they are always going to fall in that same slot, where it's one more than the molecular ion is.0970

    OK, so the take-home message is that the number of carbon atoms affects the relative height of the M+1 peak; it is usually very small, but it is going to be there.0979

    OK, well, what other isotopes are there that have high abundance?--1% is not very significant, and so it is not going to ever give rise to a really significant peak.0991

    But chlorine and bromine are two atoms that have...each of them has two isotopes that are relatively high-abundance.1002

    Unlike carbon, which is almost always just C-12, when you look at chlorine--when you look at the periodic table, you will see that it's 35.45; that is the mass that is assigned to chlorine.1013

    Well, you can't have a partial proton or a partial neutron in the structure, so of course your atomic mass units...your molecular weight is based on averages--averages of all the isotopes.1030

    But, since we are looking at single molecules and single atoms in mass spec, we need to know about the single isotopes that exist.1042

    And so, the way that, mathematically, we get this average of about 35 and 1/2 is: about 76% of the chlorine atoms are the 35 isotope, and about 24% are a 37 isotope.1051

    So, this is now going to be +2; so the naturally-occurring isotope of chlorine has two extra neutrons, compared to the lower-mass one.1066

    And so, what we are going to see is about a 3:1 ratio--if you have three-quarters...75% versus 25%, it's about a 3:1 ratio of M to M+2.1076

    We are going to have our molecular ion; if we have one chlorine, we are going to have our molecular ion, and then, +2 from that, we are going to have a peak that is about 1/3 of the size.1091

    And now, again, that is a big clue to the chemist looking at the spectrum, to see, "Wow, it looks like we have a chlorine in our molecule," because of this significant M+2 peak.1102

    OK, bromine is another example where it has an M+2; the two masses of bromine are either 79 or 81.1113

    And they are almost exactly equal--almost 1:1--so when you look at the mass of bromine, you see it's 80, but there is no bromine atom that weighs 80.1122

    It either weighs 79, or it weighs 81: because they are nearly equal and we average them together, we get the average atomic mass number of 80.1132

    OK, so what does a bromine look like?--again, very obvious when we see it in the mass spec: every fragment that contains a bromine has about a 1:1 ratio of M to M+2.1143

    We are going to get little doublets of peaks for every fragment that has a bromine in it.1157

    And so, both chlorine and bromine have a significant M+2 peak; so let's look at it one at a time.1162

    Here we have a mass spec; this is a chloroethane, so it does have a chlorine in it; now, how can we tell that it has a chlorine in it, even if we didn't know the structure of it?1168

    Well, we go to find our molecular ion, and we see that we have a lot of peaks up here; it is going to be very...this can't be our molecular ion, and then somehow we have two less from that.1177

    It is this large peak; actually, in this case, the molecular ion is also the base peak; this is going to be our M+--we'll label this as our M+, and this one is M+2.1191

    You can see that, if this one is that high, then this one is about three times higher than that...you can go a little higher; it's about three times higher than that.1205

    We'll label this one as our M+.1216

    You see the difference there: the evidence here that we have chlorine is these two peaks; the lower-mass one is about three times higher than the higher-mass one.1221

    And they are two units apart: you can count that over, see?--1, 2.1233

    Are there any other fragments in this mass spec that also have chlorine?1238

    We look, and do we see that pattern again?--well, here it is at 49; I'm sorry, we could look at this, and we could say we have 49 and 51.1243

    And again, chlorine has a mass of 35 of 37, so this fragment is big enough to still contain a chlorine atom.1255

    And so, this also must still have a chlorine, because we see that 3:1 ratio here, as well.1264

    That can tell us something about our fragments that we have.1277

    OK, now let's take a look at our bromine: this is bromobutane, and this has a molecular ion of 137.1283

    We look for 137, and here it's very, very small peaks, but what do we see?--we don't see just one peak; we see two, and they are almost exactly the same abundance.1289

    This is what we would label as M (the lower-mass one), and we describe the higher one as M+2.1299

    We describe it with reference to the lower-mass isotope; the other one is the M+2.1307

    Any other bromine fragments?--I think I see a lot of little doubled peaks--this one and this one; those fragments must contain a bromine; and fragments contain bromine.1315

    And what about this one?--here we have another doublet: one is at 79; one is 81.1332

    What do we think that is?--well, remember, 79 and 81--that is the actual mass of bromine itself; so here, we are seeing the bromine atom as the cation; so this is 79Br as a cation, and this is 81Br as a cation.1339

    There is a lot of evidence here that we have a bromine in our structure.1359

    If we have multiple isotopes, we can actually calculate--based on their known abundance, we can calculate what the ratio of the peaks would be.1370

    And of course, the computers can predict this as well.1380

    What if we had dibromomethane, CH2Br2?--let's think about what the pattern would be there.1383

    So, what are the possible masses that we have for the CH2 group and the two bromines?1389

    The CH2 is going to be 14; again, we will assume that, every time we see carbon, it is carbon-12, because the likelihood of it being a C-13 is so small; OK, so we will ignore C-13, moving forward.1396

    This will weigh 12 for the carbon and 2 for the hydrogen, so that is 14.1410

    And how about the bromines?--well, the bromines can either be the lower isotope--they could both be the lower isotope, so that is a total amu of 172.1415

    Or we could, again, have a 14 for the CH2, and we can have...this first bromine can be the higher-weighing isotope, 81 (so that would be 2 more, so this would be 174).1427

    Or, instead, we could have the second bromine (if we are kind of labeling them #1 and #2)--we could say, "Well, the first one is a 79, and the second one is an 81"; this would still weigh 174.1445

    And then, of course, the final possibility is that both of these bromines are 81; and remember, this is like flipping a coin--bromine is like flipping a coin, because it's a 1:1 ratio--it's just as likely to get a 79 as it is an 81.1458

    So, what would this final mass be?--we started at 172, and then we added 2 and another 2; so this is 176.1475

    If you flip these coins--if you pull the molecules of CH2Br2 out of a bag, what are the odds that you are going to pull out a molecule that weighs 172?1483

    Well, out of every 4 molecules you pick out, one of them is going to be a 172; one of them is going to be a 176; but you are twice as likely to take a dibromomethane molecule that weighs 174, because there are two different ways that you can reach that same amu.1494

    OK, so what are the peaks going to look like?--they are going to be 1:2:1, 1 to 2 to 1; the middle mass is going to be twice as frequent, twice as abundant, as the lower mass and the higher mass.1520

    OK, and so, here is an example: this is the mass spec of dibromomethane, the exact molecule we are looking at.1538

    We predicted 172, 174, 176, and here it is: here is our 172; now, how do you count that?1543

    Now, again, this is 160 and 200; so that means this is 170, 80, 190; so this is 170, and then 171, 172; so this 172, we would describe as M or M+; this tall peak that is twice as high is M+2, so that is what we get when just one of the bromines is the higher isotope; and then, back to the same ratio: we have M+4, because both of our bromines had the higher isotope.1552

    We get a 1:2 ratio, and so on, and so on; if you have multiple bromines and chlorines, you can calculate those, and you can use the computer to predict those peaks, as well.1585

    But these ratios of molecular ion peaks really tell us something about how many halogens we have.1597

    Bromine and chlorine are the most significant isotopes that we are going to be encountering in mass spec.1603

    Now, if we do a high-resolution mass spec--a very, very precise mass spec where we can measure very precisely what the mass of the molecular ion is--we can actually determine a molecular formula.1615

    That is because carbon-12 is defined as exactly 12 amu; that is the standard; that is the reference point; that is what we set to be 12, that number 12.1629

    And everything else is relative to that; so hydrogen, we know, is 1, and nitrogen, 14, oxygen, 16.1640

    We are going to keep a periodic table nearby when we are working on mass spec problems; we are also going to keep a calculator nearby when we are working on mass spec problems, because we are going to be a lot of math, adding up fragments, molecular masses, and so on.1646

    OK, but these are the numbers that we are probably pretty familiar with.1658

    But oxygen is 16 (I'm sorry, did I say 15?)--oxygen is 16, but the actual number is 15.994914; it is not an exact number.1661

    And so, if you take your atomic mass unit out to 4 decimal places, then you will actually see a difference, based on the molecular formula.1671

    If we find that a molecule has a molecular mass of 98 grams per mole, what are the different formulas you can have for 98?1684

    There are a lot of different ways to come up with 98.1693

    So, we have all of these different options: 4, 5, 6, 7 carbons, and so on--some nitrogens, some oxygens--but when we carry it out to very precise masses, you see that they do differ, and the mass spec, then, will be able to differentiate between one formula and another.1697

    This is a really great tool for analysis: knowing exactly what your molecular formula is.1713

    OK, so what we are going to talk about--we have kind of talked about the theory of mass spec and how it works, and the idea that our molecules kind of fragment apart, and we get this spectrum out; what does the molecular ion look like?1724

    OK, so what we are going to look at next is: we are going to go functional group by functional group, and we are going to look at their structures, and we are going to ask, "Well, what are typical fragmentation patterns that we can have, based on a given functional group?"1736

    This is going to, now, tell us something about, "OK, we have this molecule; I don't even know how much it weighs"; but by studying how the molecule breaks apart, we can help put those pieces back together and learn something about the molecular structure, on how those atoms are arranged.1751

    If we consider that our radical cation that we started with is going to cleave, and we are going to get radicals; we are going to get cations...we need to talk a little bit about the relative stability of cations and radicals.1768

    OK, so let's just look at this example: we have a carbocation (a methyl carbocation) and a methyl radical; and here is the question: which do you think is going to be more stable--the carbocation or the radical?1782

    Now, both of these are unstable; we see them as only fleeting intermediates in reaction mechanisms that we have studied, so neither of these is a stable species, because both of them are missing an octet.1795

    Remember, carbon is happy when it has four bonds; it wants to have an octet.1808

    But who is less stable, and who is more stable?1814

    Well, if you think about it, the carbocation has only 6 total electrons around it, where the radical has 7 total electrons around it; this is actually (the radical is) closer to an octet.1817

    So, it is not quite as unstable; so this is more stable--it is not quite as unstable as a carbocation.1840

    The carbocation is missing a full bond; it has only 6 electrons; it is missing so many electrons that it has a formal charge; it has a positive charge; this is going to be less stable.1849

    For example, if we think about the mechanisms we have seen, if we ever wanted to form a methyl carbocation or even a primary carbocation, we would say "no way."1859

    That reaction doesn't happen, because this carbocation is so unstable.1869

    OK, but on the other hand, when we look at radical mechanisms like free radical halogenation, you can do that on methane; you can form a methyl radical or primary radical.1873

    It is not as stable as a more substituted radical, but it is doable.1882

    OK, so if we ever have to make a choice, we are going to find that putting the carbocation in the most stable position is going to be the best choice.1887

    OK, and so, the fragmentation we are going to have is the best one that gives relatively stable (remember, none of them are super stable, but the more stable the carbocation is, the more stable the radical is, the better)...1898

    And what is a very stable radical or carbocation?--well, the most stable is going to be tertiary; tertiary is the most stable, and we have the same reason for both.1912

    If we have a carbocation here or a radical here, this is electron deficient; and so, the more carbon groups you put on here, the better, because they can donate electron density and take away that deficiency.1927

    A tertiary is the best carbocation and the best radical; that is more stable than a secondary; it is more stable than a primary; it is more stable than a methyl.1939

    The methyl cation or radical (C+ carbocation or radical--we are looking at both of those)--this is the least stable.1951

    We need to keep that in mind as we are working problems today, because we are going to be counting on that.1964

    Remember, another way to stabilize a carbocation or a radical (besides being tertiary) is: what if we had resonance stabilization?1970

    If there is a way to delocalize that charge or that radical onto multiple sites, that would be very stable.1976

    So remember, we could have allylic or benzylic; those would also be very, very stable carbocations or radicals.1982

    We'll keep an eye out for those, too.1994

    OK, so let's take a look at alkanes: if we were to take an alkane and do a mass spec, what would we find?1998

    So, for example, hexane--just n-hexane, straight chain: if we inject this into the mass spec, it gets hit by the electron beam and shoots an electron out, and now we get a radical cation.2003

    Now, what electron got removed?--we can't tell: all of the electrons here are in σ bonds, are in single bonds; so there is no easy way to draw a single bond that isn't two electrons--that is only one electron.2016

    Usually, what we do is: we just put a bracket around the whole species, and we make it a radical cation.2030

    This is just telling us that somewhere in the structure, we are missing an electron, and therefore, the structure overall has a positive charge.2038

    OK, so this is a radical cation; because it's the complete molecule, we call that M+; and hexane has a mass of 86, so we would expect a parent ion--the molecular ion--at 86.2046

    OK, but then the molecule can break apart; it can undergo fragmentation.2059

    And where can it fragment?--it can fragment anywhere you want.2062

    If we break this bond, for example, it is going to give two fragments: one of these carbons is going to end up as a cation, and the other one is going to end up as a radical.2065

    And you have a choice of one or the other--either we could have this butyl group being the carbocation with an ethyl radical, or we could have the butyl radical and the ethyl carbocation.2076

    OK, so that cleaving can occur in either direction, with the electron going to the left or the right.2088

    OK, so what is that going to show us in the mass spec?--in the mass spec and in the mass spectrum, we are going to see the charged species only.2092

    We are going to observe these carbocations: we can see this peak at mass-to-charge of 57; so 57...we'll get to know some of these numbers; we are going to see them pretty regularly, and so we'll get to know them.2101

    57 tells me it's a 4-carbon unit, so it's a butyl group; and you could also describe this as M-29; 29 is an ethyl group, so this fragment that is remaining has lost an ethyl group from the parent, and there is that ethyl group.2117

    OK, or it could fragment in the other direction, so that the peak we see is 29; and we would describe that as M-57, because it's the parent minus a butyl group.2134

    OK, so there are a few different ways we could describe that.2144

    What is another way that we could break it up?--we could break it up right in the middle here, and now that breaks the molecule symmetrically; so no matter which way this breaks, we get the same two results: we get a propyl radical and a propyl carbocation.2147

    What is going to show up here?--the carbocation is going to show up, and the mass-to-charge of this is 43, which is also M-43.2161

    We have a propyl group remaining, and we had a propyl group that was removed.2170

    OK, or we could break off one of these end carbons and fragment, and when we do that, we can either end up with the methyl radical or the methyl carbocation.2176

    And so, the two fragments that we will see would be mass-to-charge of 15 (that is the methyl group), or mass-to-charge of 71 (remember, we started with 86, so to get to 71, we lost 15 amu, and 15 is what we get for a methyl group, carbon-12 and three hydrogens, so 15 is a number we'll see a lot, too).2186

    OK, so what do we expect to find in the mass spec of hexane?2211

    We would expect to find all of these peaks: the molecular ion, and then peaks at 57, 29, 43, 71, and 15.2217

    OK, and let's see what we have here...actually, before we get to the spectrum, let me just share with you some of these common fragments.2226

    You can find lists like this in any textbook--most Organic textbooks; any spectroscopy textbooks, for sure, will have a more complete list than this one.2235

    And it is a simple list of: for each mass number, what is a common way that you can have a combination of atoms to add up to that?2247

    So, rather than you having to do the work all the time, you can just use this table to help you identify them very quickly.2259

    For example, we saw that 15 is a methyl group; so either you have lost a methyl group, or the methyl group is remaining.2268

    You can look at these as either the radical portion or the cation portion, but all of these are just fragments that would be cut off from the whole structure.2276

    That is a methyl; this is an ethyl; so when you go from a methyl to an ethyl, you added a CH2.2288

    And so, that is 14 mass units, and so we are going to be seeing that; as we go from an ethyl to a propyl, then, we add 14 to 29.2297

    Here it is--here is our propyl.2309

    This is a methyl and an ethyl and a propyl; so these numbers are going to be ones that we will probably see a lot: 15, 29, 43, and then when you go to butyl, that is another 14, so that is 57.2315

    I wrote out C4H9; it doesn't matter how those four carbons are arranged--they could be in a straight chain; they could be branched--however they are; it is still going to be a butyl group; it is still going to have a mass of 57; and so on.2334

    You see some common things here that have some carbonyls in there; we might see those.2347

    So anyway, a table like this is pretty handy to have access to and to use; so you can search online for some tables like this: just Google mass spec common fragments, and you will find some examples there, too, if you don't have a textbook handy.2352

    OK, so now, let's take a look at that hexane spectrum: here are the peaks that we predicted that we would find, and so let's see: where is 15?2369

    This is 20, 30, 40; so this is 10, so this is 15--mass-to-charge of 15 (we can bring it in here).2379

    OK, we said we would find...and notice, 29, then, is an extra CH2; 29...here is 30; so 29 is one below that.2392

    That is there; 43--this is 40, so 41, 42, 43--it's this peak here.2402

    57--55, 56, 57--so these are all pretty significant peaks, right?--pretty highly abundant peaks.2410

    71, down here: this tiny little peak is 71.2418

    And 86 was our molecular ion.2424

    I'm sorry, this isn't a peak; this is just the edge of the spectrum--sorry; that is a little misleading.2429

    OK, so in fact, we see (and remember, this is our molecular ion at 86) all the peaks that we predicted; there are more peaks than what we predicted; so again, we are not going to try and worry about every peak in the spectrum--just the ones that we're interested in.2438

    But when you look at the ones that we predicted, there are two that are very, very small--15 and 71 were not very abundant.2454

    Can we explain that?--that would be something that is useful to explain.2463

    How do we get 15 or 71?--we started at 86, so 15 means that we broke this bond, and we saw this methyl carbocation; so CH3+ would be mass-to-charge of 15.2466

    And how did we get 71?--well, 71 is M-15, so that is where we lost a methyl unit--a methyl radical; and what was remaining was the charged...the remaining 5 carbons, so a pentyl group is 71.2487

    Oh, this is a carbocation--excuse me.2513

    This is our mass-to-charge of 71, and this is our mass-to-charge of 15; now clearly, both of those are very low-occurring fragmentations, so can we see why that is--why that is not as good as some of the others?2515

    Well, think about the carbocation just formed: you just formed a methyl carbocation; that is not very stable.2531

    And in order to get this primary carbocation--this primary carbocation is stable, but what did you have to lose in order to get there?2538

    You had to cleave a methyl radical.2544

    So, this fragmentation, no matter which way it goes, produces a relatively unstable fragment; and therefore, it's less likely to occur in that position.2547

    CH3+ and CH3 radical are relatively unstable; so that is the answer to our question of, "Why are the peaks so small?"2558

    These are relatively unstable, so this fragmentation is relatively rare.2576

    It is going to be less abundant; very good.2589

    What if we had a branched alkane, instead of just a hexane itself, but we had this 2-methylhexane (is that still 6 carbons...yes, 2-methylhexane)?2593

    We have a base peak; it is telling that the base peak is at mass-to-charge of 43, and it's asking to explain why that would be.2605

    Now, remember what the base peak is: what does it mean to be the base peak?2614

    That means it is the most abundant fragment; we set this to 100%; this is the tallest peak in the spectrum.2618

    So, why would this be an exceptionally high peak?2629

    Well, remember, 43...if we go back to our little table here, 43 is a propyl group--is 3 carbons; let's just say it's 3 carbons, 36 plus the hydrogens, where 57 is a 4-carbon chain.2635

    So, we have these seven carbons; we are breaking it somehow into a 3-carbon unit and a 4-carbon unit; and which is the one that has the charge?2655

    Remember, mass-to-charge: whatever we see in the spectrum is the thing that has the positive charge, so we're going to get a 3-carbon carbocation by losing a 4-carbon radical.2664

    Where can we break this molecule that would be a favorable disconnection--a favorable fragmentation that would give a stable, a stable 3-carbon carbocation?2674

    Well, if we go to the site of the branching, if we were to cleave it in this position, we would get a 3-carbon chain and a 4-carbon chain; and the 3-carbon carbocation would be a secondary carbocation.2689

    That is relatively stable, compared to all of the other carbocations; if you broke it in any other position, you would be getting a primary or methyl carbocation; but in this one, we would get a secondary carbocation.2711

    We have removed this 4-carbon radical that was 57, and what we are left with is the 3-carbon mass-to-charge of 43.2721

    And so, yes, we would actually predict that to be a favorable fragmentation; in fact, in this spectrum, we find that it is the base peak.2734

    Let's take a look at some other functional groups: what if we have functional groups in the molecule, like an alkene--where would we expect the molecule to cleave, preferentially (more likely to cleave)?2743

    OK, once again, we are going to start with the same process: we start with our parent compound; we remove one electron from it; and we end up with a radical cation--the radical cation.2755

    We just put the entire structure in brackets to make things easy; we could just put the whole thing in brackets and put a plus radical--radical cation.2765

    OK, now where is it going to cleave?2774

    One possibility is allylic cleavage: if we look at this carbon that is next to the π bond (remember, a carbon next to the π bond we call an allylic carbon, so this is the allylic carbon), we would describe this as allylic cleavage.2776

    And if we break it there to give a carbocation, we would break off this ethyl group; it gets lost as a radical; and if we put the carbocation in this position, what is a good thing about having a carbocation in this position?2798

    It is an allylic carbocation; that is one of the best carbocations we have, because it has resonance.2811

    What does the resonance look like?--we can bring this π bond over and move the positive charge to another location; that is the best resonance that we have...no, the best stabilization that we have: it's when you can delocalize the positive charge and move it to another atom.2816

    OK, so what we are going to look for, as usual, is a fragmentation that is going to result in stable fragments, stable carbocations, and this gives us an opportunity for an allylic one--very, very stable.2833

    Now, sometimes you are asked for a mechanism, rather than just this vague dotted line saying, "Oh, we're going to break here."2846

    If you were asked for a mechanism--a reaction mechanism--to show how the molecule cleaves, well, we can do that for an alkene, because really, if you are going to remove an electron from this system, it is probably going to be one of the high-energy π electrons that gets ejected.2854

    And so, instead of just using the brackets like this, we can redraw the π bond as a radical cation.2871

    And now, when we do that radical cation, we come back to our allylic; this was allylic to the π bond; this is the bond that we want to cleave; and we can now show a mechanism for that cleavage, where we break it homolytically.2879

    One electron goes to the ethyl radical we are losing; the other electron pairs up with the radical; and again, we are losing our ethyl dot, our ethyl radical.2896

    And what we are left with is our resonance-stabilized allylic carbocation.2910

    You could see, we jumped right to this second resonance form that we had here.2918

    So sometimes, you will be asked for a mechanism for the fragmentation, and it would be a radical mechanism like this, and we would start with an explicit radical cation, rather than just kind of using the brackets.2922

    What if we have an aromatic compound, like something with a benzene ring in it?2943

    OK, now again, let's look at this molecular ion; it's a radical cation; where could we break it?2946

    Well, just like we looked for the allylic carbon as a good place to break from, this is called the benzylic carbon; and so, breaking here, we would describe this as a benzylic fragmentation.2953

    And that would be a good place to break the molecule up, because it will allow us to put the carbocation in the benzylic position.2972

    What fragment did we just lose?--remember, our radical cation is going to be cleaving into a radical and a cation.2979

    We just lost this 2-carbon...just like in the last problem, it's a 2-carbon radical, this ethyl radical.2988

    And what remains is this benzylic carbocation.2994

    Now, why is it good to have a benzylic carbocation?--because just like being allylic, this is resonance-stabilized, and we can delocalize the positive charge...and so on; etc.3000

    We could end up using all three of these π bonds that are in the benzene ring.3018

    So, this is another very, very stable carbocation to have; this benzylic resonance is very stable.3022

    And in fact, what happens sometimes when you have this benzyl cation--it can rearrange within the hydrogen mass spectrum environment; this benzylic carbocation can rearrange to this one, known as the tropylium carbocation.3035

    And this is still an aromatic system; it has 2, 4, 6 π electrons; it is aromatic.3053

    And so, when we see this peak of 91, it is either the benzylic phenyl CH2...phenyl CH2 is 91, or it may have rearranged to be this tropylium cation.3063

    It doesn't really matter what the actual structure of the fragment is, but it tells us that we had a phenyl group with a CH2 as part of the molecule, initially.3077

    When we take a look at alcohols, alcohols are going to undergo a type of fragmentation described as α cleavage; and α means it is on the very first carbon, so this is the carbon that is bearing the functional group--this is the α carbon.3094

    And so, breaking at that carbon is described as α cleavage.3110

    So, if I break off this ethyl group again...if I remove this ethyl group, it gives me the carbocation in this position, in the α position, and why is that a good place to put a carbocation?3115

    Once again, we get that resonance: any time you can come up with a resonance-stabilized carbocation, that is going to be a significant fragmentation in the mass spec.3130

    So, how does this resonance work?3138

    Well, in this case, with the oxygen, it shares its lone pairs and delocalizes the positive charge onto the oxygen.3139

    So, once again, we have a resonance-stabilized carbocation.3148

    And so, α cleavage is the place we are going to look for, for alcohols.3160

    Now again, this is another one where we can show a mechanism for that cleavage, because when we have a lone pair of electrons in a molecule, again, those are the highest-energy electrons, so those are the ones that are most easily removed when we initially do the ionization.3165

    Instead of drawing it with this bracket, we can actually remove one of the lone pair electrons on the oxygen; so this oxygen, now, has a positive charge.3185

    1, 2, 3, 4, 5: oxygen has 5; it wants 6, so this is an O+.3194

    And now, to do our α cleavage, this is the bond we break, and we break it homolytically.3200

    One electron gives us the ethyl radical we are expecting; the other electron pairs up with the existing radical.3207

    And we end up with our resonance-stabilized carbocation.3218

    And again, this kind of brings us right to the better resonance form that has a filled octet; so alcohols are another one that we can show a radical mechanism on how that fragmentation occurs.3225

    What else can we have for alcohols?--we can have α cleavage as one thing to look for; another possibility is to lose water from the molecule.3237

    In other words, M-18 may be a peak that is observed.3248

    Now, when you look at this structure, and you think, "Well, sure: I could break this bond, C-O,"--but this is not 18; this is only 17, so this would not be the correct thing: an oxygen is 16+1.3252

    So, losing water means that, first, a rearrangement must have occurred so that the oxygen gets another hydrogen on it.3267

    Then there is a cleavage, so that the fragment that is lost is H2O.3275

    So again, why is it favorable?--because you are losing a very, very stable molecule, but the mechanism is a little more complex.3279

    If you see an M-18, it might tell you that you have an alcohol, as well.3287

    What if we have an ether instead of an alcohol?3296

    We're going to do the same sort of thing: we are going to do an α cleavage, and this is the carbon that has (let me flip my page--sorry) the oxygen on it, so that is the α carbon.3298

    This is the bond we are breaking; so we would end up with a carbocation at this position.3318

    Or, now, because an ether has two carbon groups attached to it, we could look at the other α carbon; this is our α carbon, and so we break the bond from that α carbon.3327

    Remember, our goal is to get the carbocation at the same carbon that the oxygen is attached to.3338

    We can either lose this carbon group or this carbon group; we would get both of these peaks that we would expect, and why is this a stable peak?--because being next to the oxygen, we could have resonance stabilization.3345

    OK, so with an ether, we have more than one α cleavage option available to us.3359

    It is also possible that you can cleave right at the oxygen, the carbon-oxygen bond; so, in that case, you would lose an O-R radical (like a methoxy, ethoxy, propoxy, something like that--whatever that alkyl group is, plus the oxygen), leaving behind the other carbocation.3367

    The mass of this would be the mass of the parent, minus the O-R group (methoxy, ethoxy, propoxy, something like that).3390

    So, that is another possibility; so again, we have our α cleavage, and then we can also--less common, but we can also break at the C-O bond.3398

    Amines are going to be doing very much the same thing we saw for oxygens or for alcohols: we still call it α cleavage.3411

    Now, where would the α cleavage occur?--here is the carbon with the nitrogen, so that is the α carbon, and that is where we want to put the positive charge; so that is where we would be breaking the molecule.3419

    In this case, we would be clipping off this propyl group.3430

    This propyl radical would be lost, and we would end up with this CH2NH2.3434

    OK, and why is that a good place to fragment--why is that favorable?--because, just like oxygen, this nitrogen has a lone pair.3443

    It is, in fact, even better than oxygen; nitrogen loves sharing its lone pair and doing resonance, so we once again have a resonance-stabilized carbocation.3449

    So, α cleavage is very good for amines, just like with the oxygens.3463

    Now, another interesting thing that comes from amines is something known as the nitrogen rule.3471

    Now remember, nitrogen has three bonds in its stable form.3476

    Carbon, oxygen...they have even numbers of bonds (2 or 4), but nitrogen has three; so every time you have a nitrogen, it requires an extra hydrogen overall in the structure, to fill that bond.3481

    When you look at a molecular mass, almost all molecular masses are even; they end in an even number (0 or 2, 4, 6, 8).3498

    So, if you see an odd number mass, that tells you that you must have a nitrogen in your structure.3508

    And so, that is an interesting tool--a little trick that we call the nitrogen rule.3516

    So, if it is odd, then there is an odd number of nitrogens; so you have 1 nitrogen, or maybe you have 3 nitrogens--because, if you had 2 nitrogens, then that adds one hydrogen and it adds another hydrogen; we are back to an even number.3520

    The rule is that, if you have an odd molecular mass, you either have one or three or five or seven or...you have some odd number of nitrogens.3532

    And if you have an even molecular mass, you either have no nitrogens, or you have an even number of nitrogens (2, 4, 6, and so on).3539

    That is another tool that chemists have when they are learning something about a molecular mass: you will see, right away--there is a hint whether or not you have a nitrogen in your structure.3547

    What about carbonyl-containing compounds?3564

    Let's look at aldehydes and ketones.3566

    OK, now these still undergo what is described as α cleavage, but it looks a little different than we saw for oxygen or nitrogen compounds--ethers and alcohols--because it occurs right at the carbonyl.3569

    This is what we usually describe as the α carbon--next to a carbonyl, we call those α carbons.3583

    We can deprotonate α carbons and make enolates and that sort of thing.3590

    And so, the α cleavage is actually going in the other direction; it is cleaving between the α carbon and the carbonyl.3593

    And when we do that, we lose the R. here; this radical gets cleaved, and we get the carbocation at the carbonyl.3600

    This is described as an acylium ion, and why is this a good ion to have?3610

    Well, once again, we are next to lone pairs of electrons, and any time you have a vacancy next to lone pairs, we can have resonance.3615

    We can redraw that carbocation to be an O+, and it's resonance stabilized.3625

    So, aldehydes and ketones cleave on either side of the carbonyl; so this mass-to-charge would be the parent minus this R group, or we could cleave in the other way.3631

    So, if we call this A and we call this B, for B, we would have this acylium ion that is resonance stabilized.3644

    You don't always have to show the resonance; I'm just trying to make sure that you are comfortable with it and have enough experience with it that you recognize it as a good carbocation.3657

    And we also form our prime dot in this case; so we have lost an R prime; so the mass-to-charge for this acylium ion would be M minus R prime, whatever that R' group may be...methyl, ethyl, propyl, butyl--it could be a massive carbon chain--whatever it is, your molecular ion is going to weigh that much less.3666

    Now, there is another interesting rearrangement--there is another interesting fragmentation that can occur for ketones or aldehydes or anything containing a carbonyl.3691

    It is described as a McLafferty rearrangement.3701

    This is what it looks like: you are going to have your molecular ion; so you start with your parent compound; and what happens is: you kind of wrap around the molecule so that one of these hydrogens is now 6 atoms away--1, 2, 3, 4, 5, 6 atoms away.3703

    And, when you have the possibility for a 6-membered transition state, those mechanisms are always very favorable, or can be very favorable, because it is very easy for the molecule to achieve the 6-membered ring because there is no ring strain.3722

    What happens is that this π bond reaches up...we are going to form a bond here between the oxygen and the hydrogen.3736

    We use the π bond to form that bond; we break this C-H bond to form a π bond; and now, this carbon would have 5 bonds, so we have to break a bond there, and we break this carbon-carbon bond and move it over to be a π bond.3745

    It is a 6-electron system; we call these pericyclic reactions, and we have cyclic transition states--all of the electrons flowing around in the ring.3760

    And it ends up breaking (see, notice, we just cleaved the molecule between those two carbons)--we break between the α and the β carbons of the carbonyl-containing compound, and we get two fragments.3769

    Now, this fragment is a neutral molecule; we just created this neutral alkene, so that just kind of hits the walls when it goes through the magnetic deflection; this kind of falls off--we don't see it in the detector.3782

    But this is the fragment we see now.3798

    This is the charge that is observed.3802

    Now, we just made an enol; this enol would very likely tautomerize to the ketone; but the structure of the fragment doesn't matter so much--what matters is the mass and how we got there.3807

    What we would do is: if you are ever asked to do a McLafferty rearrangement, it really helps to actually draw out the intermediate that is formed, the intermediate transition state that you are getting, because you will notice: it is not just a matter of breaking this carbon-carbon bond; you also transfer this hydrogen from this carbon chain to this carbon chain.3823

    There is a 1-unit difference in this original carbonyl portion that remains.3846

    What do we expect from an ester?--an ester can do a few things: it can undergo α cleavage, so just like any carbonyl, it can undergo α cleavage.3857

    We can lose this R. to give an acylium ion.3868

    It can undergo a McLafferty rearrangement, so one of these sides can wrap around and form the 6-membered ring and cleave that way between the α and β carbons.3873

    Or, it can lose RO.; so just kind of like we saw for ethers, that also corresponds to an α cleavage here.3884

    You could kind of treat it like a ketone; it can break on either side of the carbonyl, or it can possibly undergo McLafferty rearrangement.3893

    Let's try some problems, now that we have had an introduction to mass spec and thinking about the various fragmentation patterns that are possible.3903

    Let's try a few problems.3914

    OK, so for example, "For the given molecule, mass of 57"...that is actually...you know how I knew I had a typo?--why can this molecule not have a mass of 57?--because that is an odd mass, and there are no nitrogens in the structure.3916

    Look at that: I just realized that I have a typo (and see, I corrected it in my notes, but not on my slide).3934

    So, actually, it has a mass of 58, which you can calculate if you need to (so again, always have that calculator handy); but a lot of times, you will be given the mass.3940

    The question is: do you expect the more abundant peak to be mass-to-charge of 15 or mass-to-charge of 43?3948

    If we use our cheat sheet, 15...how do we get to 15?3956

    15 is a CH3, so that would be a CH3 carbocation; and 43 is actually 3 carbons; so 15 is one carbon, and 43 is three carbons.3963

    Remember, you had 36, and then you add in the extra 7 hydrogens.3975

    So, this is a 4-carbon...I'm sorry, 3-carbon (I just said 3 and wrote 4); so we are going to be breaking this molecule up, this 4-carbon molecule, into 3 carbons and 1 carbon.3981

    If this is the only place we can break it to do that, how do we get these two different fragments as a result?3995

    Well, remember, let's start with this as a radical cation, because that is the only way it is going to cleave.4003

    Let's assume it is a radical cation; and now, we can break it so that the propyl group ends up with the radical and the methyl is the cation, or the propyl group is the carbocation and the methyl is the radical.4011

    OK, so the question is: which of these do you expect to be more likely?4030

    They are both forming unstable methyl species, but which one is even less stable?--this methyl group is less stable than the radical.4035

    We would expect that this primary carbocation is more stable, even though it had to kick off a methyl radical; that is OK--that is better than having this methyl carbocation.4050

    This is less stable.4069

    We expect...who do we expect to be more abundant?--the more stable; this has the mass-to-charge of 43; it is going to be more abundant.4072

    This is the better fragmentation.4085

    OK, very good.4091

    OK, now we have a molecular ion of 74; so again, we can kind of assume this is a radical cation, so that that is our 74 for the M+.4096

    And the same thing--we are asking, "Who is more abundant: 31, 45, or 59, and how do we get those?"4112

    OK, so now we have to think about our structure and think about how to break it apart.4120

    59...a mass-to-charge of 59: what size fragment have we lost?4125

    We started at 74; so it looks like this is -15...4134

    In fact, these are good problems for you to try, if you want to pause the lecture and try each of these on your own, before I do the discussion of it.4139

    This is really good practice because, based on what we have had so far, you really should be able to work on these problems on your own.4147

    The mass-to-charge of 59 is -15; so that means it cleaved like this to leave a peak of 59.4154

    45, mass-to-charge of 45, is M-29; so 29 is our ethyl group, so that means we cleaved off this 2-carbon unit.4167

    And the mass-to-charge of 31 we could describe as -43, which is a 3-carbon unit, so now we are breaking it like this.4184

    Which of these three bonds are we breaking?4201

    And so, you think about an alcohol, and you say, "Which of these is more likely--is there one that is going to be more favorable than another?" and you think about the carbocations that we form, either at this carbon or this carbon or this carbon.4206

    Which is going to be the most favorable carbocation?--it's going to be the one where the carbocation is at the same carbon as the oxygen.4221

    So remember, we described this as α cleavage; we said α cleavage is very stable; it is very favorable, because the carbocation we would get is resonance-stabilized.4228

    OK, and so, not only answering the question we just asked (which do you expect to be most abundant?)...so the mass-to-charge of 43 we would expect to be the most abundant; but your answer should extend beyond: "It's most abundant, because it's α cleavage, and that is what I learned."4251

    You want to look at the other possibilities and show that that is actually the most stable carbocation.4274

    If we had this carbocation--it's just a random primary carbocation, not very stable--and if you took off the methyl group, we would have this carbocation; these are just primary carbocations and no resonance stabilization.4280

    You want to demonstrate why the α cleavage is preferred over the other possible fragmentations.4295

    OK, here is one more to try: Explain why the mass spectra of methyl ketones typically have a peak of mass-to-charge of 43.4305

    So, provide the structure of this fragment and a mechanism for its formation.4313

    First of all, what does it mean to be a methyl ketone?4318

    A ketone has 2 R groups on either side, and a methyl ketone tells us that one of those sides is a methyl group.4322

    And what fragmentation do we expect as a common one for ketones?4332

    Well, for ketones, we can break on either side here; and so, if we take a look at cleaving in this position, that would cleave off whatever that...4338

    This is why it is common: it doesn't matter what that other carbon group is, because it gets lost in this fragmentation, and what remains is this unit.4350

    Is that 43?--well, we can check our cheat sheet if we have it; otherwise, we could do our old-fashioned...we have an oxygen; we have carbon times 2; we have hydrogen times 3.4362

    We really have to be able to do this math, either in our head or with a calculator if we are allowed.4373

    This is 16; this is 24; and this is 3; and we have 43.4379

    OK, so don't hesitate to do this math and do the calculation; you don't want to make an assumption or think it's "close enough"; you really want to verify that.4386

    This certainly would have a mass-to-charge of 43, and that is the fragment that is there.4395

    What if we had to show a mechanism for this?4401

    Well, if we consider the molecular ion...so right now, this kind of assumed that this was the radical cation; so remember, this fragmentation isn't something that happens with neutral, stable molecules.4403

    This only happens after we ionize the molecule; we form a radical cation; it is a very high-energy species; and then, that is how we break it into a radical and a cation.4417

    So, make sure you are starting with the proper species.4427

    What we can show is: instead of using the brackets, we can show one of the lone pairs of electrons on the oxygen being removed.4431

    In that case, it's the oxygen that is the radical cation.4445

    And so, what does my mechanism look like?--this is the bond that I'm breaking, so we are always going to break that homolytically.4451

    We are going to lose the R.; we lose the R., and then this electron pairs up with the radical that was here; so that brings us, right now, to a triple bond.4456

    We call this an acylium ion.4470

    That is the way that we can show the mechanism for this α cleavage; we call this α cleavage for a ketone.4476

    OK, so now we have a mass spectrum of this given molecule; the mass is 88.4489

    Account for the peaks at mass-to-charge of 45 and mass-to-charge of 57.4497

    So, mass-to-charge of 45 is going to be...well, we started at 88, so this is M-43; so 43 is our 3-carbon unit.4502

    And mass-to-charge of 57 is M-31; now, 31 isn't a number that is common to me, but 57 is; this tells me that it is a 4-carbon unit, a butyl group.4523

    This is a propyl group; this is a butyl group.4539

    Whether you are looking at the mass, trying to learn something from the mass of the fragment--the cation...sometimes that works, and you can find a connection there and where to disconnect, but sometimes it's looking at the mass of the fragment that is lost, the part that is lost; you are looking for a recognizable thing.4541

    Here I see we have a 3-carbon chunk being lost; so here is my propyl group (1, 2, 3); that looks like a good disconnection here.4562

    If we call this a and b...so this would be disconnection a; and mass-to-charge of 57 means we are left with this 4-carbon chain; we are left with this butyl group, so this must be disconnection b.4571

    In other words, these are both common peaks we would expect for the mass spec of an ether.4590

    This one is minus...losing an OR., and so this is the fragment that is left here.4600

    And this is the α cleavage; so here is our α carbon, and we are doing α cleavage.4609

    For the 45, we have lost the propyl group, so we have done our α cleavage, and that is resonance-stabilized.4618

    And for b, we are remaining with our 4-carbon unit; so this is -OR.; we have lost a methoxy; and for a, we have done our α cleavage.4638

    And, in this case, the α cleavage has lost a propyl group of 43.4664

    OK, so it just asks for a count for the peaks; add those two masses; it doesn't say to show a complete mechanism or something, so we can just kind of do this work in our heads.4670

    And keep in mind that if you don't have a table that adds up 45, that you can do the math here, of your 24 and 16 and another 5; and this is 4 carbons and 6, 7, 8, 9 hydrogens.4685

    OK, so make sure you do the math to double-check that.4701

    OK, this is another common type of problem we have in mass spec; it's "How would you use mass spectrometry to distinguish between the following two compounds?"4707

    They both have the same mass; they both have a molecular mass of 73; and the question is: how is their mass spec going to differ?4717

    They both have molecular ion peak; but what other peaks are we going to expect, that are abundant, for one or the other?4728

    OK, and this comes from knowing what the common fragmentations are for your different functional groups.4735

    So, for an amine, what we are going to do--where would this amine typically break up--the most common place for this to break up?4740

    You are thinking, "Where is the best place for me to break a bond so I result in a carbocation that is going to be a stable carbocation?"4746

    So remember, we call this α cleavage, and it is going to be at the carbon attached to the nitrogen.4757

    We are going to break here to put a positive charge on the carbon with the nitrogen: α cleavage to give this resonance-stabilized cation.4767

    OK, so that is what we would predict for butylamine; this is methyl propylamine, and where can that break?4785

    Well, here is the carbon; it can lose a hydrogen, so we might expect that there might be a significant M-1 peak here, but let's look at the carbon-carbon bond that we are breaking.4794

    Here is our α carbon; here is our α cleavage in this case; and we would expect to form this carbocation.4806

    And again, why there?--because it's resonance-stabilized.4818

    We can draw both of those forms.4824

    What would we see in the mass spec?--well, over here we have lost a propyl group--that is M-43 (that is one way you can kind of calculate it based on the molecular ion).4833

    This has a mass-to-charge of 30; nitrogen is 15, and carbon is 12...am I adding that up right?4849

    Mass-to-charge of 30...oh, and we are missing a hydrogen; so the reason that this is not even...the M+1 rule with the even and odd numbers (this is something that is interesting to point out) is: that is for whole, complete molecules.4860

    OK, when we are looking at mass-to-charge ratios of fragments, by definition, a fragment means it's not complete octets; there is somewhere that someone is missing a bond; so in this case, then, a nitrogen-containing fragment is going to be evenly numbered, because we are also missing, let's say, a hydrogen or something like that.4876

    So anyway, mass-to-charge of 30 makes sense here--it's M-43--where in this case, we lost an ethyl group, which is 29.4895

    And when we calculate this mass-to-charge, we get 44.4907

    When we take the mass spec of these two amines, we expect to find a significant peak for butylamine at a mass-to-charge of 30, and a significant peak in the methyl propylamine at mass-to-charge of 44.4913

    Not only could we distinguish between those, sometimes we are actually given the spectra and asked which is which--you know, "match them up," kind of like you might have with an IR problem--here are the IR spectra; here are your possible structures; match them up and provide evidence to defend your choice--how did you make your choice?4927

    OK, so here we said (this is how we would use mass spec), "and provide the structures and the mass-to-charge values for the significant fragments expected."4946

    You not only want to have "Hey, this should have a peak at 30, because of α cleavage," but you show what that structure looks like; and the same here.4956

    OK, finally, let's try a McLafferty rearrangement, because that is kind of a unique phenomenon we have.4966

    And so, we start with 114, and there are two questions here: one is "what is the fragment resulting from a McLafferty rearrangement?" and then there is a second question: "What accounts for the peak at mass-to-charge of 57?"4976

    We can do either one we want; let's look at the 57.4997

    So, what size...so 57 is actually a butyl group, and we started at 114, so it's actually -57; so we have either lost a butyl group or we still have a butyl group--you can kind of look at it that way.5003

    And so, where could this molecule cleave that would be both reasonable for the functional group...5017

    It's always very important--we don't want to just start hacking the molecule apart in whatever way suits us; it has to be something that is logical for that functional group.5026

    And so, what we saw for ketones is that it can break on either side of the carbonyl; so if we break on this side, then that would lose a butyl group, and that would give this acylium ion (carbocation--I just draw it as the other resonance form); and this has a mass-to-charge of 57.5035

    So, this underwent α cleavage to form 57.5060

    So it turns out that a butyl group has the same mass as an ethyl group plus a carbonyl.5064

    Again, that is where that table kind of comes in handy; you can see a few different options for how to get to a certain mass--how to achieve a certain mass that you are looking for.5071

    OK, so that is the mass-to-charge of 57 fragment; now, how about this McLafferty rearrangement?5081

    What we want to do is: we want to look around; this oxygen is going to look to either side, and it is going to find a hydrogen that is 6 atoms away; we have to form a 6-membered ring.5088

    So, if this is 1, 2, 3, 4, 5, 6...it is going to be taking one of the hydrogens from this end carbon, and that hydrogen is going to be transferring it over.5100

    You can try and do the mechanism with the structure drawn out, just in the straight chain; and maybe with practice you can get there; but let's draw the mechanism with the 6-membered ring first, to get some practice with that.5113

    Again, if you want to pause this and try in on your own, this is a great one to try on your own, rather than just see the solution.5131

    We're going to draw our CH2, and then a CH with a methyl on it, and then a CH2, and then there is that hydrogen that is 6 atoms away.5136

    If we want to number our carbons, 1, 2, 3, 4, just to keep track of everyone--1, 2, 3, 4...5147

    OK, any time you are redrawing a structure, doing rotation, something like that, numbering your carbons is a really good way of keeping track and making sure we don't lose anyone.5155

    OK, so that is the bond that is formed; what does the mechanism look like?--we could show this carbonyl grabbing onto that hydrogen; it forces this bond to break; it forces that bond to break.5163

    OK, so where is the cleavage that occurred?--it's right here, and it's right here; between the α and the β carbon is this bond you are always going to break with McLafferty rearrangement.5175

    OK, so what do we have on the left-hand side of the molecule?5185

    We have...I'm sorry, this is a CH3, CH, double bond, CH2; this is a neutral molecule that is not observed.5192

    OK, but what is left...no, I'm sorry; you know what, I keep making this mistake.5203

    Before I can do a McLafferty, I have to have a radical cation; I have to have a radical cation before I can do my cleavage, the α cleavage, before I can do a rearrangement; I need to have a radical cation.5213

    So, this clips off as a neutral molecule; it is still this radical cation that remains.5227

    This is what is going to be observed--the enol is the fragment that is going to be observed in the mass spectrum--of course, as the rearranged ketone.5235

    This is C4 (1, 2, 3, 4) H8 (2, 4, 5, 6, 7, 8) O....C4H8O; so we can do that math, and we get mass-to-charge of 72.5246

    That is another peak that we would expect to find in this molecule, thanks to the McLafferty rearrangement.5264

    We have had an introduction to mass spec, just kind of the theory about it and how we might use it to learn something about a molecule's structure.5270

    And so, hopefully, you can find a good book to work on some extra problems until you get the hang of it and be able to handle it.5278

    A lot of times in more advanced classes, you will have spectroscopy problems where you need to come up with a structure, and you will be given all the spectroscopic information about that compound.5285

    "Here is the molecular weight; here is the IR; here is the NMR; here is the mass spec."5296

    And so now you will know how to take that mass spec information and really work with it and come up with some structural information.5302

    Thanks so much for joining me, and I hope to see you again really soon.5312