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Lecture Comments (69)

1 answer

Last reply by: Professor Starkey
Fri May 13, 2016 11:20 AM

Post by Mohamed E Sowaileh on May 11 at 01:59:30 AM

Thank you for the immediate response. I am very grateful to you for the invaluable help you gave me. May God bless you.

3 answers

Last reply by: Professor Starkey
Mon May 9, 2016 3:37 PM

Post by Mohamed E Sowaileh on May 8 at 09:16:38 PM

Dr. Laurie Starkey,

I hope you are doing very well,

Someone has never taken a deep and comprehensive general chemistry course, do you recommend him to take G. chemistry courses to have a solid understanding in chemistry, because I guess organic chemistry then would be a lot more easier than if I didn't take G. chemistry. am I correct? or do you think that the quick review you made is quite sufficient? I appreciate your help.

 Thank you.  

2 answers

Last reply by: Apolonia Gardner
Wed Dec 2, 2015 12:40 AM

Post by Apolonia Gardner on November 24, 2015

Hello,

I am a high school senior about to send off my applications for college. I am stuck on one thing – my intended major. Biology and chemistry have been my favorite courses throughout high school, and I would like to get a college degree that will enable me to perform research with viruses. My lifetime goal is to find a cure for a disease. From your experience, what undergraduate major should I shoot for? Biochemistry? Microbiology? Molecular Biology? Immunology? Chemical Biology? Organic Chemistry? Pharmaceutical Science? Any guidance is appreciated.

5 answers

Last reply by: Professor Starkey
Mon Jun 8, 2015 1:26 AM

Post by Jinbin Chen on June 5, 2015

Hi, Dr. Starkey!

I have watched some of your lectures to prepare for the national chemistry olympiad exam, and even though the pace of these lectures are kind of fast, I really like you explanations and passion for organic chemistry.

Right now, I am planning on doing organic chemistry in my freshman year of college with the help of AP credits. Do you have any suggestions on things that I should do in the summer to adequately prepare for organic chemistry?

1 answer

Last reply by: Professor Starkey
Wed Jan 7, 2015 7:44 PM

Post by Galymzhan Tuleushov on January 6, 2015

wqs

1 answer

Last reply by: Professor Starkey
Tue Dec 16, 2014 1:27 PM

Post by Rene Whitaker on December 15, 2014

I don't have a question, I just want to thank you.  I relied on rewatching your videos to prepare for my cumulative final in Orgo I, which was a national standardized test.  My professor said 50% is the average score on the test and I got an 84%.  With the exception of synthesis, which will forever be my nemesis, I find your lectures to be extremely understandable and helpful.  THANK YOU, THANK YOU, THANK YOU!!!  Now, you just have to get me through Orgo II.

1 answer

Last reply by: Professor Starkey
Mon Jul 21, 2014 10:22 PM

Post by Saria Abbas on July 21, 2014

I have a couple of past papers but no answers to them, some are visual mechanisms, is there a way I could send you questions and/workings out for feedback?

1 answer

Last reply by: Professor Starkey
Tue Feb 4, 2014 8:56 PM

Post by Habib Awes on February 3, 2014

1. which are the properties of ionic and covalent substances? illustrate by reffering to: Sodiaum chloride, diamond and methene.
2. the substances which is ionic, please detail your resoning.
3. now the chosen covalent substance, may you detail your reasoning.

1 answer

Last reply by: Professor Starkey
Fri Dec 6, 2013 6:22 PM

Post by robina saeed on December 6, 2013

Hello Professor,
Just a quick question.  I have never had Organic Chemistry and I am planning on using this course preparing for the MCAT.  Good idea? take care

1 answer

Last reply by: Professor Starkey
Sun Dec 1, 2013 1:49 PM

Post by matatio manoah on November 30, 2013

Just wondering which subject is more based on energy chemistry or physics

1 answer

Last reply by: Professor Starkey
Thu Nov 28, 2013 7:14 PM

Post by Jennifer Akiga on November 28, 2013

I've studied up until Alcohols! You're an awesome teacher and explain well. I just wish I could fastworward the slides, they take ages. Helped me a lot in my test.

2 answers

Last reply by: robina saeed
Fri Oct 18, 2013 1:14 PM

Post by robina saeed on October 16, 2013

Is this a complete college course?

1 answer

Last reply by: Professor Starkey
Tue Oct 15, 2013 8:05 PM

Post by yannick Haberkorn on October 12, 2013

thank you so much for this grea

1 answer

Last reply by: Professor Starkey
Sun Sep 29, 2013 1:54 PM

Post by Hannah Barker on September 23, 2013

Professor Starkey, I am taking Organic Chemistry online this semester and I stumbled across these lectures and I bought a subscription. But my question is, can you tell me what lectures would correspond with my text book chapters? I have tried to compare the contents and sub titles of the lectures with my textbook but i havent figured it out yet. My book is "Organic Chemistry"- 9th edition by Francis A. Curey and Robert M. Giuliano. ISBN #-9780073402741

I can send the chapter titles also if you can not pull them up by that information.

Thank You!

1 answer

Last reply by: Professor Starkey
Thu Sep 5, 2013 1:13 PM

Post by Atreya Mohile on September 5, 2013

Do we have to remember the structures of the organic compounds, that are mentioned in the lecture, like cholesterol, etc? (Sorry for incidentally posting previous question 2 times).

1 answer

Last reply by: Professor Starkey
Thu Sep 5, 2013 1:05 PM

Post by Atreya Mohile on September 5, 2013

Further, in applications of SN1 and SN2 type reactions, is it required to have a grip on Chemical kinetics ? I mean, that can the questions be asked, that are based on the mixture of organic chemistry and physical chemistry in SAT subject tests or AP?

1 answer

Last reply by: Professor Starkey
Tue Sep 3, 2013 9:38 PM

Post by Riley Argue on September 1, 2013

Thank you.

2 answers

Last reply by: Professor Starkey
Tue Aug 13, 2013 7:30 PM

Post by Jeffrey Zhang on August 13, 2013

Are there any Prerequisites for this course?

1 answer

Last reply by: Professor Starkey
Tue Aug 13, 2013 7:31 PM

Post by Jeffrey Zhang on August 13, 2013

These Lectures are great! Are there any lecture notes or problem sets which we can work on?

1 answer

Last reply by: Professor Starkey
Fri Mar 1, 2013 11:19 PM

Post by James Bond on March 1, 2013

How do you know the geometry of a molecule? It's great that it can help determine if there a a net dipole or not.

2 answers

Last reply by: Professor Starkey
Fri Mar 1, 2013 11:26 PM

Post by Joshua Domingo on March 1, 2013

Every time I take a break, I am unable to fast forward. This is very time consuming. Is there anyway I can fast forward without waiting for a buffer?

1 answer

Last reply by: Professor Starkey
Thu Jan 3, 2013 10:02 AM

Post by wow love on January 3, 2013

Thanks

1 answer

Last reply by: Professor Starkey
Sun Nov 25, 2012 12:14 AM

Post by John Delva on November 21, 2012

why you cant fast forward to the lecture that you want????

1 answer

Last reply by: Professor Starkey
Fri Oct 19, 2012 10:55 AM

Post by Donna Perygin on October 17, 2012

Very good. A lot to throw out there in the first lecture. You might scare a few off, but very good.

1 answer

Last reply by: Professor Starkey
Sun Jun 24, 2012 10:32 AM

Post by abdualrahman m.abdualkader on June 23, 2012

My English is not that good especially in listening, so subtitles could be very helpful for me.

1 answer

Last reply by: Professor Starkey
Sun May 27, 2012 12:26 PM

Post by Magesh Prasanna on May 26, 2012

In the examples of polymers,styrofoam-TM,
spandex-TM, what TM represents?

I enjoyed your teaching! Thanks a lot!

0 answers

Post by Jerusalem Mulatu on April 27, 2012

You're really good with your explanations! Thank you

1 answer

Last reply by: Professor Starkey
Thu Oct 27, 2011 11:00 AM

Post by Alain delice on October 27, 2011

very detailed lecture, I wish my teachers would such an interest into teaching as you do; is it possible to get hand out of your lecture, maybe through a link on this website, it would very helpful.

1 answer

Last reply by: Professor Starkey
Wed Apr 6, 2011 11:44 PM

Post by jean philius on March 17, 2011

Does significant different mean big difference....to me it looks like hydrogen has a significant difference with carbon...meaning carbon is all the way to the right and H is to the left

1 answer

Last reply by: Professor Starkey
Sun Feb 6, 2011 10:05 PM

Post by Laura Diamond on December 23, 2010

HOw do you know they have two valence electrons?

Introduction and Drawing Structures

Ionic or Covalent?
F2
Covalent
Ionic or Covalent?
LiBr
  • Li+ Br
Ionic
Ionic or Covalent?
NaNH2
Ionic
Draw a skeletal sctructure for the following molecule: (CH3)2C=CH(CH2)4CH3
Draw a skeletal sctructure for the following molecule: CH3CH2CH2CH2CH2CH3
Draw a skeletal sctructure for the following molecule:

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

Answer

Introduction and Drawing Structures

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

  • Intro 0:00
  • Organic Chemistry 0:07
    • Organic
    • Inorganic
    • Examples of Organic Compounds
  • Review Some Chemistry Basics 5:23
    • Electrons
    • Orbitals (s,p,d,f)
  • Review Some Chemistry Basics 7:35
    • Elements & Noble Gases
    • Atom & Valance Shell
  • Review Some Chemistry Basics 11:33
    • Electronegative Elements
    • Which Is More Electronegative, C or N?
  • Ionic & Covalent Bonds 14:07
    • Ionic Bonds
    • Covalent Bonds
  • Polar Covalent Bonds 19:35
    • Polar Covalent Bonds & Electronegativities
  • Polarity of Molecules 22:56
    • Linear molecule
    • Bent Molecule
    • No Polar Bonds
    • Ionic
  • Line Drawings 26:36
    • Line Drawing Overview
    • Line Drawing: Example 1
    • Line Drawing: Example 2
    • Line Drawing: Example 3
    • Line Drawing: Example 4
    • Line Drawing: Example 5
    • Line Drawing: Example 6
  • Diversity of Organic Compounds 33:57
    • Diversity of Organic Compounds
  • Diversity of Organic Compounds, cont. 39:16
    • Diversity of Organic Compounds, cont.
  • Examples of Polymers 45:26
    • Examples of Polymers

Transcription: Introduction and Drawing Structures

Hi welcome to educator .com.0000

This is our first lesson in organic chemistry and let us start by defining what it means to be organic.0002

These terms were starting to be developed hundreds of years ago.0007

Things were being classified either organic or inorganic.0011

Organic, was described as something that came from living things plants and animals and the matter form those species and inorganic was everything else so things like rocks and minerals.0016

Rocks and minerals never came from living matter, metal, glass for example.0031

These are some materials that are described as inorganic and other than these sorts of things they are known as organic.0041

Now we have expanded that definition to not just being things that come from a natural source but we have expanded it and defined as the chemistry of carbon.0048

This is because our life is carbon based and that it encompasses the original definition.0058

So it is true that things that living things and things that came from living sources are going to be organic.0066

But we can expand our definition to include a lot of other interesting things.0071

Now, what I love about organic chemistry is that it surrounds us in our everyday lives, and I was really fascinated by the topic when I took this as an undergraduate.0075

Let us go through some examples of things we will encounter throughout the course.0083

The products that we used that improve our lives, we’ve heard lots of examples of organic chemistry in medicines, drugs, about the entire pharmaceutical industry is that majority of those products are organic compounds.0088

Carbon containing compounds, including pesticides, herbicides, fungicides and things that protect our crops, and help feed people; dyes, inks, things that are of colored, pigments, things at non colored to things colored to be organic.0100

Paints, in the paint industry it’s very important to study organic chemistry and understand how we can make the paint be longer lasting or more environmentally friendly.0116

Gasoline, fuels, the petroleum industry is using organic molecule.0127

We distill crude oil into its various components.0135

Each of those components are organic compounds and we find it that they burn very quite nicely, it provides energy.0139

Cosmetics, shampoos and perfumes and those sorts of things -- so the personal care industry is also something that definitely involves organic chemistry.0146

A lot of materials that we use in our world, natural materials as well as manmade materials...0156

So if we take a look at the structure of paper or cotton you’ll see that those are carbon chains, carbon containing compounds as well as rubber and tires and things that are made up of rubber.0162

But then there are a lot of manmade examples of these compounds which are polymers so they have these long chains of molecules like we do for cotton or rubber.0174

So some manmade ones or things like nylon and polyester those are organic compounds.0184

All plastics that you can imagine vinyl that’s organic as well as adhesives.0190

So anything that is sticky or gluey is also an organic molecule.0195

Liquid crystals if we think about our LCD displays that we have on our phones and our televisions, those are organic molecules, a lot of interesting research going on there, as well as nanotubes.0199

Nanotubes are all carbon containing structures that are extremely strong and this is one we are looking into, nanotechnology.0209

Nanoorganic chemistry is really leading the way and I’m sure we’ll have some very exciting breakthroughs in the years to come.0220

And In nature remember that organic chemistry is initially defined as having this relationship to living systems and it’s still quite true.0228

So if you look at the structures of proteins, fats, sugars those are all organic molecules so anything we eat or we digest is an organic molecule.0235

The vitamins that are also essential to our existence, things that we can taste or smell those are organic molecules that we are interacting with flavors and fragrances,0244

hormones, steroids, structures of DNA.0254

When you look at the field of biochemistry, these are all organic reactions in living systems.0258

And so that’s why it’s critical to have a strong foundation in organic chemistry before we move on to biochemistry because you are going to be studying organic reactions that are taking place in living system.0274

As you could see there’s a lot of interesting things that are in store for us and as an organic chemist there is a wide range of industry in which you could be involved, the pharmaceutical industry, petroleum, food, health and beauty, polymer the list goes on forever.0288

As a matter of fact, I was a Biology major when I took organic chemistry as an undergraduate and I was so excited about the topic and found it so interesting that I ended up changing my major to chemistry and studying organic chemistry in graduate school.0304

Let’s see what we have in store before we can get into some with some of the really fun stuff.0318

Let’s make sure we review some chemistry basics because anyone taking organic chemistry should have a year or so of general chemistry.0323

While you’ve learned a lot in general chemistry, there are certain things that are going to be really critical to succeed in organic chemistry so I want to make sure we review those so that you’re ready to hit the ground running.0330

So for example, let’s think about electrons.0341

Electrons are the things that are going to be doing all the bonding, doing the reactions and so it’s really important we have an understanding of how the electrons look like, how they behave.0344

Remember these are held in atomic orbitals around the nucleus so we have s, p, d, f those sorts of orbitals.0353

For organic chemistry we’re mostly just dealing with this s orbitals and p orbitals that’s what carbon has available to us and we are studying the chemistry of carbon.0360

If we think of the s orbitals and p orbiatals, let’s consider their energy and their relative energy.0371

If you remember the very first shell of electrons has just a single orbital, the s orbital that’s available to it.0380

That is the 1s orbital we call it.0390

Then we move it to carbon it now also has a second shell of electrons and in that shell we have two types of orbitals that are available.0393

We have an s orbital but because it is now farther from the nucleus it’s going to be higher in energy so what I’m showing here is relative order of energy.0400

The 2s orbital is higher in energy than the 1s.0411

Then the p orbital, it has a node, it is dumbbell shaped; these are further still from the nucleus.0414

The p orbitals are higher in energy still and if you recall there are going to be three different types of p orbitals in that second shell so we can draw them at the same level and this is the 2p.0423

What we want to remember this general description of relative energies and the s orbital is going to be lower in energy meaning more stable than the p orbital.0436

It’s going to be important to us down the road so I just want make sure we have that mind.0450

Let’s take a look at the periodic table and again we’ll see here just a section of the periodic table because carbon is the atom we’re going to be most concerned with, we going to be involved throughout this whole year of organic chemistry.0457

Really very few other atoms are going to be involved in our organic molecules, definitely hydrogen.0472

A lot of hydrogen in our molecule is attached to carbon, there may be nitrogen, oxygen some of these halogens.0479

Possibly we’ll see some of these down here, the silicon, the phosphorous even the sulfur.0485

But really it’s just very small region of the periodic table that we’re going to spend the most of our time with.0492

But some of our reagents and reactions do involve some other atoms as well.0497

You’re going to remember what’s very important about the periodic table is that these atoms are the most special here.0502

These are the noble gases and these elements are extremely stable.0507

Every other atom in the periodic table every other element is trying to walk like the noble gases.0513

What that means is they want to have the same electronic configuration.0520

That imparts a special stability because an atom is going to be stable if it has a filled valence shell.0525

That’s going to be the ultimate goal that all atoms are seeking and we know this as the Octet Rule.0533

Hydrogen can never have an octet because it only has a 1s orbital so it can only hold 2 electrons.0540

So for hydrogen, it will have a filled s orbital and that would be very stable.0549

But for carbon and nitrogen and all the others we want to have in our outer shell two electrons in our s orbital.0554

We want to have six electrons in our p orbitals, this would be a filled shell.0561

Now it moves all the way over to give a configuration that will be like Neon, Argon or Krypton depending on what atom you are looking at.0566

For example if we take a look at sodium, sodium metal this is not a stable atom on its own because it has just one valence electron but if sodium was to give up a valence electron to be Na+ that would bring it back to have the electronic configuration of Ne making it extremely stable.0576

So anytime we see Na as part of the formula, we know that that sodium has to be Na+ if it’s going to be stable.0599

How about something like Ca or Mg something in the second column here.0607

Well, these have two valence electrons that’s not a filled shell so the way that they can end up with the filled shell is to get rid of those two electrons so we have thing like Mg2+ it’s very stable Ca2+.0613

Those atoms like you have +2 charge.0628

Again anytime see them in the formula we know that we can think of that charge, Li, K will have a +1 charge.0631

How about the halides, F, Cl Br what would make them stable.0640

Well, to get all the way to Cl, we have to go 1,2,3,4,5,6,7 Cl has 7 valence electrons so it will have just one more then it will have the electronic configuration of Ar that would be very stable because it will have a filled octet.0645

So how can I do that, well, it can gain an electron and have a negative charge that would give it instead of 7 valence electrons it will have 8 valence electrons and will have a filled octet.0661

The periodic table is a critical resource for us and just a quick glance of the periodic table is going to remind what charges certain atoms like to have of course the atoms on the far left would like to have positive charges, the atoms in the far right will have negative charges.0672

We also learned something about electronegativity and that’s going to be a concept that is important in organic chemistry allows us to predict certain things.0693

The one rule that we know here is that F is the most electronegative element so the periodic trends are such that as you move towards F moving either to the right or moving up that is going to increase your electronegativity.0703

What does it mean to be electronegative?0727

It means you pull electron density towards yourself.0733

Fluorine is very very good at pulling electron density towards itself.0736

Now I’m not going to share with you the table of the numbers because we don’t need to memorize the numbers, we need to build just kind to have a feel for who’s more electronegative and who is not.0740

A few things that we should point out - F is the most electronegative atom.0752

You should also know that O is the second most electronegative atom.0756

So anytime you see an O you know right away that that O is pulling electron density towards itself.0766

That’s a good fact to know.0775

It’s also difficult to compare things that are not within the same column or the same row so it’s also good to know that carbon has very similar electronegativity to H now they are not the same number but there is not a significant difference between those two.0777

So it’s good to remember that those have had similar electronegativities.0796

When you look at the electronegativities of N and Cl those are equal so that kind of help to balance it out.0801

Typically you are not having to memorize this numbers if you know that F is extremely electronegative and we know that O is also extremely electronegative that’s going to get us through a lot.0813

If you’re comparing any two atoms that happen to be in the same column or the same row then for sure you would be able to compare their electronegativities.0823

Comparing C to N, which one will be more electronegative?0832

Here’s C, here’s N. Since N is closer to F then N is going to be more electronegative.0838

Now let’s talk about bonding, how do these elements come together to form bonds?0845

We have two types of bonds, the ionic bonds and covalent bonds.0853

Ionic bonds is what we’re going to have if we combine atoms which have large differences in electronegativities so if we take something like Na which is on the far left of the periodic table and combine it with Cl which is on the far right of the periodic table.0857

I have shown them here with just their valence electrons, Na has one Cl has seven, neither of these species are happy these are very unstable they are very reactive because neither has a filled octet.0872

The way that they can end up satisfying this problem is we can have a transfer of an electron; the Na can give up its electron and give it to Cl.0887

What happens now is that Na loss an electron so it’s positively charged, the Cl gains the electron so its negatively charged.0901

As a result of these transfer of electrons you have stable filled octets.0912

So we are going back to that octet rule and we are going back to achieving that noble gas configuration.0920

In this situation it would be very useful to transfer that single electron and both would be satisfied.0928

This is described as a salt and ionic bond is a representation of a salt if you have a + and – charge and it’s a network structure.0937

So it’s not correct to describe NaCl as a molecule.0948

There is no such thing as a molecule of NaCl.0956

There’s 1:1 ratio of those two.0958

But every Na+ is surrounded by Cl- in the salt crystal structure.0960

Try not to call it a molecule although that does happen sometimes accidentally but instead it is a salt and it is a network structure.0966

Let’s take a look at a different example where a transfer of electron will not be so good and when we are going to have that is when we are going to have covalent bonds rather than ionic is when we have atoms with similar electronegativities.0977

With Na and Cl, Cl really really wanted that electron because it is so electronegative and Na did not want that electron because it is so electropositive and so the transfer makes sense.0992

In a case where like this where we have a C, C has 4 valence electrons and if we combine that it would be four H atom each with a single valence electrons.1004

The idea of each of those H donating electron to C to fill its octet is not a good idea because C then would have 4 extra electrons and would have a -4 charge that would be highly unstable.1012

So instead, what we do is we share the electrons.1025

This is still unstable just like before because no one has a filled octet but if we were to share the electrons between the nuclei so that this H now that sees 2 electrons (remember that’s the filled octet for H and that it gives it the noble gas configuration).1028

The C now sees 8 electrons, everyone gets a filled octet but we don’t have any charges.1050

This is a stable situation and that these three lines kind of mean that the equivalent of this is instead of drawing this two shared electrons as 2 dots what we do is we draw a line to represent what is known as a covalent bond.1057

So every time we draw a line connecting two atoms this represents two shared electrons.1082

Let me call that a covalent bond.1091

C is very good at forming covalent bonds that’s why so many of its structures are so stable and drew out so many different types of interesting products and compounds.1097

By doing this bonding and sharing these electrons we now have again stable filled valence orbitals so this is a good arrangement.1109

And what we have now is this methane (we will going to be learning these names shortly) and this is a molecule.1124

This is a discrete molecule.1133

This is a discrete stable group of atoms that is independent of other molecules, so this is a methane molecule and it has a covalent bonding.1136

So the way we decide between ionic and covalent is we compare the atoms that are coming together and decide if they want to be shared or if they want to transfer the electrons.1146

If they are coming from the same area of the periodic table like C and all the neighboring atoms around C those are going to be preferred to be covalently bonded.1155

If we see anything off on the far left of the periodic table the metals those are going to be charged species and those will always be ionic species.1163

Is there anything between strictly covalent or strictly ionic?1176

In fact this is kind of a continuum it is not always clear quite whether something is completely ionic or completely covalent.1183

Especially when you are looking at a covalent situation, when you have two atoms that are sharing electrons those two electrons does not necessarily means being equally shared between the two atoms because those atoms may not have identical or very similar electronegativities.1190

In that situation we have what is known as a polar bond or polar covalent bond and that if so we have a significant difference in electronegativity.1205

So let’s take a look at the C - O bond do these have the same electronegativity or similar electronegativity?1215

What do we know about O?1222

We know O is the second most electronegative atom in periodic table so we know that this O is very electronegative and what is happening is that it pulls electron density , this two electrons being shared by the C and O are being pulled toward the O and so they are not equally shared.1224

And what we have is a polar situation or a dipole situation here where the O is δ -; we use this δ symbol to represent a partial charge and the C is δ+.1242

So there’s a couple we can show this polar bond we can draw this arrow line points in the direction of the electrons being drawn or we can have a δ+ or δ- to represent to represent the electron deficiency on the C or the electron richness of this O.1258

How about the C-H bond?1278

Do those have a significant difference in electronegativity?1281

Again we need to know this by looking at the table, in fact they do not have a significant difference so this is described as a non-polar bond because there is no significant difference in the electronegativity.1284

This C-O bond we describe is a polar bond and this is a non-polar bond.1300

We need to be able to describe bond this way.1316

How about if we have a C attached to a halogen, the letter X is going to represent a halogen?1320

Whenever we see that in organic chemistry the X will represent something like F, Cl, Br, I.1327

Remember F is the most electronegative so for sure that’s the most electronegative and in fact it does decline throughout but except for iodine it’s a little less extreme.1333

But for the most part when you attached an X to a C you do expect electron density to be pulled toward the halogen so we have a δ- and a δ-+ and these are also polar bonds.1349

This is going to be important to us because this is going to help describe the relationship of these carbons when they are in this structure, this C is electron deficient and it’s going to have certain reactivities as a result of that.1360

Now when we are looking at the molecule as a whole we could decide whether that molecule is polar or non polar but in doing so what we would have to consider is the geometry of the molecule or the shape of the molecule.1374

Here’s an example, this is a CO2 and the geometry of this molecule is shown, we’ll know later how to predict the geometry of the molecule but this is only a molecule.1387

Although this C-O bond is polar, when we see those two vectors, we see that they are pulling equally in opposite direction which means they cancel out and they have no net dipole moment.1399

So this is actually a non polar molecule.1417

So in determining the polarity of the molecule, not only do we need to look the polarity of the bond but then we have to determine the relationship of those polar bonds with another see what the overall dipole moment is.1419

Here we have a molecule which is a bent molecule we have the same C-O bonds that are pulling in the direction of the O and while they both have the right and the left components cancel they both have an upward component and there is nothing to cancel that in the downward direction.1432

So this does have a net dipole moment and so we describe it as a polar molecule.1452

How about this next one, here we have a bent shaped as well but what polar bonds do we have?1458

We know that C-C bonds are non polar, we also know that C-H bonds are non polar.1469

So because there are no polar bonds there can’t exist a net dipole moment so in this case it does not matter what the geometry is because we have no polar bonds.1474

So this is a non polar molecule.1482

Any molecule with just Cs and Hs will have to be non polar.1486

Let’s look at this last one NaOH.1492

What we know about the bonding of this species, NaOH?1494

I just said, if we have a formula containing something like Na, what do you know about Na?1500

How does Na exist in order to be stable?1508

It must be positively charged.1510

So this is actually an Na+ which means this OH must be an OH Na-.1513

This must be anionic compound.1518

You are going to be able to make that evaluation if you are looking at formula.1520

So what does it really look like?1523

It looks like we have Na + then for an ionic bond we don’t draw a line between the two we just show the two ions next to each other and we have an OH-.1526

This is the actual structure of sodium hydroxide NaOH.1535

This is ionic. We don’t describe this as a polar molecule we describe it as an ionic molecule because it has a full charges.1541

It doesn’t have a δ+ and δ-1550

We could also show up here that this O is a δ- and this C has some δ+ character because of that polarity.1553

This has full charges not partial charges.1564

We describe this as an ionic rather than polar.1569

An OH-, this here is described as a covalent ion because it is an ion it is negatively charged but it has covalent bond as well, the bond between the O and H shared covalent bonds.1571

We call it a covalent ion.1587

So NaOH has both ionic and covalent bonds in the structure.1589

Finally, as a little bit of an intro and a catch-up let’s talk about the use of line drawings for organic chemistry because this is a shorthand notation that organic chemists use constantly as a way to save some time.1595

What we do is we draw a line to represent carbon chains and the definition is that any endpoint of a line represents a carbon and any intersections or bends represents a carbon atom.1612

For example this carbon chain has 1,2,3,4,5,6,7,8 Cs; so the way that this can be represented is the 1,2,3,4,5,6,7.1630

So this zigzag line or line drawing notation represents the carbons.1646

This end point is a C and any bend here or intersects to this two lines 2,3,4,5,6,7,8.1652

What we do is we draw the lines to represent the Cs and then we omit those Hs that are attached to those Cs.1663

We can do that because we know that C likes to have four bonds to be stable.1673

So we know that this end C has just one bond shown to a C we know the other three bonds must be the Hs.1678

So this must be a CH3. Any line that ends at a point is a CH3.1692

And this C, what do you know this C looks like?1701

It has two bonds to Cs and so the other two bonds must be the Hs. This is what a -CH2 looks like.1705

Very quickly we can draw very complex organic molecule by using this notation and we need to have some experience with that to recognize that there is a lot of Hs on these structures that are not really shown.1712

So this eight C organic molecule known as octane we are going into some nomenclature down the road and we’ve heard of octane that is one of the components of gasoline.1727

You have the octane reading when you fill your car up.1740

This is one example of an organic molecule being good fuel with these some other compounds that we use in our car.1744

What do we do if we have an atom other than C?1753

So we just draw that atom so we have two C chain 1, and then we have an O attached to that.1757

Now this H you have to include.1764

We only omit the Hs attached to Cs so all other Hs are shown.1767

So this represents this structure, this is called ethanol or ethyl alcohol.1772

There are many alcohols we will learn as a class of compound but this is the alcohol that is grain alcohol.1780

It’s the kind that is drinkable.1788

This molecule we can draw this in line drawing what we will be doing is replace those Cs.1790

So if we have a double bond or a multiple bond we just connect two points with a double line instead of a single line.1800

This molecule is called acetic acid and this is the compound that is in vinegar that gives its characteristic smell and taste.1807

So this carboxylic acid groups looks like easy to find, have acidity to them that’s because of that bite and kind of burns a little bit when you taste vinegars.1820

So there is again organic chemistry in flavors and fragrances.1830

How would we represent this one?1833

Well we have a C=O and then we have a C and then we have a double bond to another C so you could draw it this way.1837

Or you could draw…it doesn’t matter what angle we do we’re going to be showing actually how this molecules kind of rotate around and you’ll see some different shapes and conformations.1846

In a lot of times in this particular case, we like to show these Hs.1856

This is kind of a one exemption to the rule where we leave off the Hs usually shown.1862

This H when it’s attached to a C=O we use to draw it that way.1868

It’s acceptable to leave it off but don’t be surprised when you see it on there still.1877

Carbons not only can make very long chains but they can also for rings so have cyclic compounds.1881

So when we have a six-member ring like this we simply draw a hexagon.1888

So cyclic compounds are very easy to draw with line drawings by just drawing the polygon, a pentagon or a square.1893

This also has three double bonds so we would just show that every other C is connected by two bonds and we could leave off all these Hs we don’t need to do that1900

we know because there’s 1, 2, 3 bonds shown so there must be a fourth bond and that’s the H.1913

So this is the representation of benzene, this molecule is called benzene.1919

That is an interesting molecule.1924

This is actually known to be carcinogenic that means it causes cancer.1928

Benzene is one of the many dozens of carcinogenic compounds that are in cigarette smoke.1932

We will be seeing chemistry of benzene related compounds down the road.1938

Some of the exercises that you want to do is being able to convert from condensed formulas to line drawings back and forth to get some experiences because we really want to become fluent with this line drawings.1943

It’s going to save you so much time down the road.1955

You’re also going to have to be able to work with them so you need to be able to interpret that.1957

For example, this is pretty complex, we have a C with three CH3 groups1961

so here is that C and we just draw three lines coming off to represent those CH3's and then it is attached to a C and see all this C have no Hs on here.1967

That tells me that there’s a triple bond.1980

There’s a triple bond between those carbons because there are no Hs, and then we have another C with two chlorines on it.1984

So very funny with the line drawing for a complex molecule but this condensed formula takes a lot of deconvoluting as you work it out as well.1995

We are going to be spending a lot of time talking about how to draw Lewis structures and come up with these various line drawings and formula so this is just a brief introduction into the process and rules.2008

But what’s nice is that now that you have an understanding of what this line drawing represent now we can take look at some examples of just how diverse organic molecules can be.2024

For example this very first structure is called vanillin, why do you think it’s called vanillin?2036

This is the major component of vanilla extract, the vanilla bean and so this is what tastes and smells like vanilla.2043

You know if you are to buy artificial vanilla, it would be this compound, just the vanillin or the natural extract will have mostly vanillin but then also dozens or maybe hundreds of other constituents in there because it is very rich, deep flavor compared to the artificial which has just this one component.2052

Look at this structure, this is it.2072

It is just a benzene ring, we can see a benzene ring in here and just carbons, oxygens and hydrogens, that’s it, but depending how those atoms are put together they can have completely different reactivities and behaviors.2075

This next molecule is interesting again just carbons, hydrogen, oxygen.2087

This molecule is called carvone.2092

I built a model of carvone here, we’re going to be looking at some of these three dimensional shapes called stereochemistry when you consider the three dimensional shape of a molecule.2094

We have a six-membered ring in here and we have some double bonds.2104

And what’s so interesting about this molecule is on the six-membered ring we have this group, if this group is in this position, compared to this position it will have a very different flavor and fragrance.2108

In one position it will taste and smell like spearmint, like you might have a gum.2123

In the other position, it smells and tastes like a kerwin.2127

We’ll see some really fascinating changes that happen by considering the stereochemistry, the three dimensional shape of certain molecules.2131

Now I said everything that we eat and digest is an organic molecule, let’s take a look at some of those structures.2140

This is the structure of a protein.2146

So when we heard of proteins these are amino acids that are linked together.2148

This R group here, whenever we use the letter R it just means that we have some kind of carbon chain.2153

So there’s a wide variety, I just gave you a basic structure here depending on what that R group is and depending on the order in which these are put together and how long it is it’s what defines what protein you have and how does that behave as an enzyme, what functions does it have in the body and so on.2159

But look, it’s a carbon and nitrogen chain but definitely organic molecule.2175

This is a structure of sucrose it’s called table sugar or cane sugar has this.2184

All sugars, starches, saccharides are organic molecules, carbon, hydrogen, oxygen, that’s all we put them together this way.2191

Here we have a six-membered ring with an oxygen, here we have a five-membered ring with an oxygen and they are linked by an oxygen bridge.2199

Sometimes we draw bonds with some shading, we draw this as a wedge and that’s another way to represent three-dimensionality, stereochemistry.2206

If the bond is wedged that means it’s projecting out toward you, if it’s dashed it means it’s behind the page so it’s kind of hidden.2217

That’s something that maybe you can understand what you’re seeing when you’re looking at these line drawings.2224

Down the road we’ll explain in much more details so you will really have a great feel for these structures.2231

This is the structure of triglycerides so when we’re looking at lipids, that’s oils, greasy things that has this general structure where it has this three-carbon chain with this three oxygen groups on it.2236

I just put an n here because these are really really long carbon chains.2251

Sometimes they have double bonds in them, sometimes they are all single bond and that makes the difference between saturated or polyunsaturated or monounsaturated fat so we know how important those are.2255

That is all explained by looking at the structure of the organic molecules involved.2267

So fats, sugars, proteins everything that we are digesting is organic.2272

All of the compounds undergoing reactions involved in our body are organic.2276

This is the structure of cholesterol, it’s a steroid.2284

Any steroid in the body has a similar structure.2287

This group of four rings kind of defines the steroids structure then various groups attached to it make it one or the other.2292

We know how important cholesterol is to our health.2300

Here’s the structure of vitamin C, again carbons, hydrogens, oxygens that’s it but if we put together this way, this now is an essential vitamin and keeps us very healthy, really important part of our diet.2303

And you can see here that that structure have been elucidated with some stereochemistry was shown.2317

Here is a one component of a DNA; we know DNA is that double helix that goes on and so these are the groups that link out to make each of those long chains.2322

You could see again kind of a sugar backbone here, kind of looks like the sugar part is only a five-membered ring and then some groups that look a little like benzene ring with some nitrogens in there and some phosphate group here.2335

DNA are blueprint for our reproduction is also an organic-based molecule.2348

Then of course the pharmaceutical industry and drugs of any kind, things that affect our central nervous system, on our body in any way, almost all of these are organic molecules.2357

This is the structure of aspirin, very simple molecule of carbon, oxygen and hydrogen with the benzene ring in there.2372

That’s the structure of aspirin.2380

Remember I said benzene itself is carcinogenic, but just having the benzene unit as part of the structure does not mean it will also be carcinogenic.2383

Obviously aspirin is actually good for your health in many cases and it has pain-relieving and fever-reducing effects.2394

As soon as you attached groups to the benzene ring it’s no longer benzene itself and has very different physical and chemical properties.2409

Here’s a structure of nicotine, so that’s the component in cigarette that makes it so addictive.2418

Here’s caffeine, you could see a lot of drugs have nitrogens in them they have a lot of reactivity that we will be studying throughout organic chemistry.2424

Here’s a compound that is colored, so this called Orange-2 which is used as a dye and it turns out that having these double bonds one after another like this, having a large network of double bonds like that.2433

It’s called the conjugated pi system, having those interact with light in such a way that they we can see them as colored,2446

They reflect certain colors of the spectrum and so that’s an example of a pigment that is organic based.2454

This is the structure of Roundup a commercial herbicide that is used as weed killer and again if you have weeds growing in your yard or termites invade your house or cockroaches we are expecting that there’s a product out there that will kill those or take care of the weeds.2463

So there’s a research to make them safe for humans as possible, safe for crops as possible but get rid of the pests, and the fungus and all that and the weeds so that we can protect our crops and that they’ll have to grow in healthy and safe way.2487

This molecule always fascinates me, this is an example of pheromones.2504

A pheromone is an example of the chemicals that insects used to communicate with one another.2509

This is a sex pheromone and so this is what the housefly uses to attract the mate.2516

It lets off this chemical and them a fly of the opposite sex is going to be attracted with that and so they can be together to mate.2523

And look at this structure, it’s just a giant carbon chain, has one double bond here with this particular stereochemistry with both pointing to the same direction and that’s it, if you take that double bond no effect on the housefly.2533

If you have another groups somewhere else no effect.2546

I really find it fascinating and interesting.2548

And you might wonder why do we know with the sex hormone of the housefly looks like, what application could we gain from that.2552

Well, let’s think about maybe a roach motel type thing where you have bait that you have some poison in for ant trap or roach trap or something like that or a yellow jacket trap those are things you might have seen.2560

Well, we put them under the sink we can’t just hope that they randomly walk in there and eat on the poison, we need to find some way to attract them.2576

Wouldn’t it be a great idea to take the sex hormone for that insect and put it in a box so that when a roach is walking by kind of turns around and says --2583

“hey, there’s a party in there and let’s check that out”2593

And they go in and of course there’s just poison for them to feed on and then they take that back to their colonies and then they can wiped out the whole colonies.2596

That’s not by accident that they are being drawn to this box and so pheromones could have an important role in that.2603

Here’s a brief structure of a carbon nanotubes; so if you look at it very closely you could see that it’s a benzene ring fused with another and another and another.2610

When you fuse benzene rings together to get a sheet, to get a flat structure. in fact that is the substance called graphite, that’s the structure that we have in pencils and that allows you to trace a line across a piece of paper.2620

That is a graphite.2635

Well if you take that sheet and roll it up you’re going to make a tube, and this is a tube that you could extend for a very long distances because C-C bond is so strong.2636

It’s a flexible yet extremely durable strong lightweight material and so nanotubes are really revolutionizing a lot of materials.2647

You’re seeing it being used for creating a really strong durable bicycle that’s super lightweight that you can carry easily, those sorts of applications.2659

Do keep an eye up in the future for nanotechnology and you most often see organic chemistry at the forefront of that.2670

Then here’s an example of a polymer and a polymer is described as a long chain of carbon atoms with repeating units.2679

This is called polyvinylchloride so you could see we have a chlorine here periodically these goes on and on in each direction and it is called PVC for short.2691

So if you have heard of PVC piping that the piping that we use for water pipes and if you have sprinkler system in your yard it called PVC pipes.2701

So this is an example of what an organic polymer looks like and by varying the group that’s hanging off and the spacing of those groups and maybe the interaction between the chains you can have a tremendously different physical properties.2710

Let’s take a look at some of those.2725

I have a slide here which only have a very small set of examples of polymers, we just talked about PVC, that is something that you have in your pipes, your shower curtains, how great it is to have something that is water resistant and mold resistant in order that we can use it in our showers.2727

The car seats we have in our car that are vinyl.2746

Polyurethane is something that we can make kind of foamy so things like mattress or soles of your tennis shoes or they can be used as a fiber for spandex clothing very stretchy so some polymers might have that stretchy physical property.2750

Polystyrene is also something that you can foam up so it is very lightweight.2769

Styrofoam is a polystyrene or depending on how it is processed and how it is cast you can also make it hard and see through like for plastic cups or not see through and the plastic toys are made up of varieties of different polymer.2774

Polyethylene is the plastic that you used for some plastic wrappers, sandwich, there’s a few different polymers that you could use for that.2795

Polyacrylamide is the polymer which is super absorbent of water so that they really can hold a lot of water and last a long time.2804

Adhesives are also polymer based so things that make tapes stick, post it notes, all those sorts of things, anything sticky or gluey is going to be as an example of polymer .2817

Teflon is an example of polymer, that nonstick coating that we have in our pots and pans is a polymer.2829

Polymethylmethacrylate is what is used as a plexiglass so the huge walls that you have in aquarium that are really thick and really durable, those are examples of plexiglass as is the plastic in eyeglasses and contact lenses those are also polymers.2837

The fibers and fabrics, obviously some clothes are 100% cotton but those do not stretch very well, they kind of sag over time. They don’t hold the color very well.2856

And so by using manmade fibers we can not only dramatically vary our clothing but also make it a lot more durable and stain resistant and all those interesting properties so things like nylon, ryon, polyester additives to your clothes.2869

Polyacrylonitrile is what we have for carpets so carpet fibers also are synthetic to make them a lot more durable and longer lasting.2888

Then you can even have polymers that are incredibly durable even stronger than steel in some case like kevlar which a polymer that is used for lightweight bulletproof vests, on tires they use them for bolt holes to make them very strong.2899

If you think back to thousands of years ago on how did someone protect themselves in battle.2920

Well they put on a metal helmet and a coat of armor that is all metal and they had to walk around with this and probably needing help getting dressed and its very heavy and you get very fatigued very quickly.2926

You have no visibility because they did not have any plastic shields they could go over.2941

Now you’ll think of today’s military and the lightweight, movable fabrics that they have that are bullet resistant and really protect you but also allow you to function, the goggles that are plastic and see though and are durable and protect us.2950

Really as you can see in just with this very brief introduction that what we’re going to learn in organic chemistry.2969

It really does affect in our everyday lives and we’ll find examples of it all around and I look forward to exploring more with you and we’ll do that in the future.2976

Thanks very much for visiting educator.com.2989