Lecture 01. Introduction to Carboxylic Acids.
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Nowick, James
This is the third quarter course in the organic chemistry series. Topics covered include: Fundamental concepts relating to carbon compounds with emphasis on structural theory and the nature of chemical bonding, stereochemistry, reaction mechanisms, and spectroscopic, physical, and chemical properties of the principal classes of carbon compounds. 
 Monday, Wednesday, Friday, classes end up being 10-11, 11-12. I've kind of split the hour from 10.30 to 11.30. But honestly, if you want to try to see it other times, come on by my office. There should be no doors usually open. There shouldn't be an excuse I can't make to office hours. In terms of getting a touch with me this way, patch me after class or during my office hours, particularly for questions involving organic chemistry where there are structures involved, it's very hard to communicate about technical matters by email and just honestly, they're too good at checking my email. Let's see, the other thing, if you, the other people who are going to be very, very important to you in the class are teaching assistants, Johnny Pham and Kim Lee. And I picked two of the best graduate students from my laboratory to serve as teaching assistants. Johnny and Kim, do you want to stand up? So, Johnny and Kim are going to be handling the discussion sections, and so you'll get to know them in the various discussion sections for the course. They've set office hours on Wednesday and Monday, and they meet right in the area outside of my office. So you'll be able to meet with them, and I posted their email addresses here. So, the textbook for the class is the Smith Text, which you've been using. I won't go a whole heck of a lot into it. I think it's a pretty good book. I'm going to put emphasis on various parts in the lecture. The break up to me, you'll get a feeling for what I think are some of the most important aspects of the book. Some of the material, I'll sort of final directly out, but I think they have a really good way of liking things. Some of the things I'll pull from other notes of my own, you'll get a feeling for my perspective on them. Ultimately, what I want to be doing with them is sharing my perspective on the Smith Text, which I really love and am passionate about. Organic chemistry is so central to life and to all of its functions. Johnny and Kim are both earning their PhD in organic chemistry and are working on health-related problems. Johnny is working on how to understand his research, how to understand and control protein aggregation with Alzheimer's disease using organic chemistry. Kim is working on protein interaction in cancer and in HIV transmission, again, using organic chemistry. The thing that we're going to learn in this class is central understanding all of life's processes and in terms of developing new medicines. The textbook for the class, as I said, is pretty good by now. Probably none of you are going to be doing this, but if you want to get the electronic, if you're coming in, say, from having been in a different quarter elsewhere and you want to get the electronic version, that's available as well. Now, organic chemistry classes are really only a whole piece of the picture. The biggest picture for organic chemistry is not reading a textbook. It's not just coming to class. That's sort of the basis. But the real part is active learning. And organic chemistry, in particular, you learn by actively processing problems. One of my developments in this section is I can't do what I've done in the honors class. The honors class has students get rated feedback from the GAs. It's also a much smaller class. And it's really just so incredibly valuable. You're working and wrestling with a problem set in a deadline to have to actually work the problem in your set. And the other thing, of course, that's wonderful is deadlines. I hate them, but I love them for myself. I mean, it keeps me on focus. And this is, of course, one of the greatest wonders that I've ever done in the past. It's easy to fall behind as a class. And so what I've done is the next best thing that happened with Johnny and him, where homework is signed into individual. And that is you won't have electronic homework, who's that for the work, I know. How many of you have used this in previous quarters? So most of you are familiar with this system. This has been the first year I've adopted this system. I consider it to still be a work in progress. This is the first time. There's a lot of junk out there. I've been watching for years with textbook companies coming up with their own quick multiple quick. The first point, I think it's getting close to thinking of life-organic plans. It's not perfect. It's a little clumpier on the implementation than I'd like, but it's a baseline. It's a starting point. On top of that, we're going to have problems that you work and present in the discussion section. And there are homework problems which, alas, are too much sort. Have the answers key with them so you can always check yourself. But I know, I know, I know there's this temptation when you're working problems to look at the problem, say, oh, I understand it, or I think I understand it, then look at the answer key. And that is such a short circuiting to the learning process. And so I urge you, I beg you, if you want to master the material, don't do that. Actually write out the answer, commit, and then go ahead and look at the answer key. And I know it's hard to have the result. So, all right. So you have the website for the course, and let's see. So we have discussion sections for the class. As I said, we're going to be working the problems, working problems in most of these. I've made them match up to the chapters in the course for running through chapters 19 through 25, and then we're jumping to carbohydrate in 27, and then the last week we'll do some special topics from amino acids and from some of the chemical chemistry. And so I've matched up the discussion sections to them. You need to be enrolled in a discussion section. It's best to go to the one you're enrolled in, but if you can't make it to the one you're enrolled in, there are other discussion sections you can go to. It's a little confusing how I've juggled things, because we miss Monday discussion sections. We're going to hit the ground running on Tuesday. Discussion sections in the first half of the course are going to run Tuesday to Monday, Tuesday to Monday each week. Then at the midterm, we're going to switch. We'll have a block of discussion sections from Wednesday to Friday, right after the midterm, which will be going over the midterm. I urge you to come to it. It's a great way to learn about things that you didn't understand. And then for the course after the midterm, our discussion sections will be running Monday to Friday, Monday to Friday, and if you're in the Memorial Day one, you'll just pick up one of the others. If that sounds confusing, don't worry. I've put a link here, and you can go ahead and see the schedule for discussion sections so you never miss out. So that's just on the syllabus website. Friday had two discussion sections that had very low enrollment, and so we closed those discussion sections. I urge you to come to the, I think it's the 12 to 1230 on Friday instead, but if that doesn't work with your schedule, just pick another discussion section. All right. This is the first time that I've taught this particular section, and so I've set up our schedule in advance. I think it's all going to work, but you should check the website just in case we make any changes in the scheduling. So I've set up all of our reading assignments for the year up here, and I've set up our first homework assignment and its deadline, and then others I've set the deadlines, but I'll be getting the problems up there. The problems should be up about a week in advance. If you're not seeing the problems about a week in advance, send me an email, and I'll let you know if there's anything wrong with the posting. Sorry. Like for the homework assignment, some of them say not to be submitted. Ah, great question. So the question is, for the homework assignment, some of them say not to be submitted. So the Sapling one supports you to submit online. I would love to be able to see your paper written out of homework. In fact, you would make me incredibly happy if you come to my office, if you ever don't understand something, and bring me a big sheet of sloppy, messy papers with pencil scrolls with all of your efforts on the homework. If you come to my office, bring your notes. I don't know if you don't understand. I want to be able to help you. I want to see your homework. But as much as I would love for Johnny and Kim to be able to actually bring their homework, they can. So the second best thing to having homework that's actually due to hand in is problems from those textbook homework assignments are going to come back to you on the quizzes. So the quizzes, you're going to have seen all of the problems before. The quizzes are going to have problems that are taken directly from the discussion section and from the Smith-Pomer problems. The discussion section problems won't have answers. You won't be able to get them online. So you've got to go and visit the discussion sections to see the problems and to discuss them. Alright, homework's always a conundrum, particularly in the context of the issue of academic honesty and reading. I've really thought before you about this issue for homework because I see it as different from the exams. My hard-to-feeling opinion on homework is I want you to learn by doing the problems. Some people like to work problems alone. Some people like to work problems in group. My primary feeling is learning. And so I've really set up the network. If you get a problem wrong, it poachers you. You get a chance to do it over. There's just a small penalty. So for working in groups, my philosophy is it's okay to have real peer learning to be learned in every community. What's not okay is to just be approving a person's answers and then to be mindlessly typing them in to the standpoint. That's not learning. That's not teaching. If you're actually communicating and understanding from a peer, you're learning how to communicate. You're better reinforcing the ideas in your mind and your peer, in turn, is actually learning. And next, the attitude for working in groups that I would see on the homework problems. Alright. So, got to come to the lecture section. You're going to miss things if you don't. I've set up this course on video. Videos for the course will be available if you have to miss the lecture or better still, if you want to miss the lecture. You can download them. We're going to get them on YouTube. The open courseware site produces the I. The I tunes used so there will be lots of ways to access the material for review. But come to the class. Alright. So, quizzes. We have six quizzes. As I've said, the quizzes are going to come directly from the homework assignments and from the discussion section problems. The quizzes are on the dates that I posted here. We don't have make up quizzes. We drop the lowest quiz. Any quiz that's missed counts as your own. I think that we drop the lowest quizzes. Quizzes are returned through the electronic thingamajig here. I think you're all familiar with electronic exam return. Yeah. Yeah. So, you'll get your quizzes back through that. Quizzes count for 20% of the grade. The midterm exam, which is on Tuesday, May 8th and covers chapters 19 to 22, is on. Counts for 25% of the exam. The final exam is on June 12th and counts for 45% of the course and the homeworks count for 10% of the course. There'll be a seating assignment chart for the midterm and for the final exam. I won't have seating assignments for the quizzes, although I appreciate it if you try to spread out and choose an empty seat without a neighbor if possible. You do need to bring a picture ID. The UCI ID is the best thing. A driver's license would be the alternative for the midterm and for the final exam. You'll be passing them down the aisle and the DA's will be matching your face with the ID and the exam, you know, the assigned seat. And during the exams, you need to have that. All right. All right. Academic honesty. You all know a cheating is copying off your neighbor, getting materials in an appropriate way. Don't do it. It is fatal. You will get a zero in the course. A note will go into your file and you will be able to go on with things that require this. Two students in my previous class of 1051 received a failing grade for cheating. And one friend of them who wasn't an enrolled student but colluded received a note from his class. So don't do it. Cell phones. We all have them. We all love them. We check our email on them. We get text messages. Take them away in class. Away. Off. No buzzing. You vibrate if it doesn't distract you. I find my own distracting if it vibrates because it means, oh, there's something in my pocket that I now need to know on. Just turn it off. Don't get me cell phone. If you don't. If you're distracted by your cell phone, I will send you out. All right. By now you probably know about enrollment in these large classes. The professors don't handle any of that. It's done online and through the undergraduate office and there's all the contact information. Tutoring. Best place to get help. Me, Johnny, Cam, office hours, discussion section, their office hours coming by. If you want to get some help through tutoring, there's LARP. Chemistry also makes tutoring services available for free and they'll have information that's posted. And then I already blasted you with an email. I thought this was actually pretty cool what the chemistry department was offering. So while they're focusing on this particular homework or that particular homework they recovered and all the topics and I feel like that's pretty good. That's important here. So anyway, let's see if there's anything else that I want to talk about. I think that pretty much covers it. Oh yeah. I'll be giving you some software. I paid about 700 bucks for this software. It's great for visualizing molecules and they said I could give it to all my students and they said they could use it for research. It's really cool for looking at molecules. We'll use it later on to look at sugars and understand some of your theory of chemistry. And so during one of the discussion sections, the TAs will be working with you to help teach you how to set that software. Who has a laptop computer or portable device in the class? Good number of you. Bring those to that discussion section. That will be the week of, they will help you set up on your computer. That will be the week of April 17th through April 23rd. Then we will remind you again. Alrighty. Well, I think that about covers it. So, questions on the syllabus. So of course. So our discussions are running. The questions went through the discussions starts. So we'll start on a Tuesday and run through Monday. So Tuesday, Wednesday, Thursday, Friday, Monday will be the same as the first half of the course. Up through the midterm and then after the midterm will have three Wednesdays and midterms on a Tuesday. So Wednesday, Thursday, Friday will be the same as the first half of the course. So the quiz schedule. The quiz is, check the syllabus I believe there on Thursday, the first half of the quarter and Tuesday the second. Alright. Other questions? Well, I'm really enthusiastic about teaching this particular course. This is in my opinion the most exciting quarter of organic chemistry because we get to learn all the good stuff. All the stuff. We've got to leave all this groundwork in place. You've learned about stereopenistry. You've learned about alkane, and alkene, and alcohol, and texting on our cell phone. So you've learned about all of this incredibly, incredibly cool stuff. And now we've come to what in my opinion is the richest, the most wonderful stuff in organic chemistry. And most of the class, seven weeks, is going to focus on carbonyl chemistry. Broadly defined. We are going to start off with carboxylic acids. And the carboxylic acid family. We're then going to work on to aldehydes and to ketones. Aldehydes and ketones have just a fantastically rich chemistry. They have chemistry of reactivity at the carbonyl group. They have chemistry of reactivity at the adjacent carbon. Alphabetum saturated carbonyl compounds have chemistry of reactivity of the alkene part of the molecule. Carboxylic acids. We're going to start off. Chapter 19 is kind of funny. It's sort of just a little book of throwaway chapter in carboxylic acids. Just the taste of it. But carboxylic acids constitute a big and important family. And so we're going to learn about members of the family. We're going to learn about esters and amygs. And then we're going to move on in about the eighth week of the course to talk about amines. And then we're going to spend the ninth week of the course talking about carbohydrates, sugars. And finally, if everything goes according to schedule in the tenth week of the class, we'll have some selected topics from chapter 28. Chapter 28 is on amino acids. And so it's sort of a refrain of carboxylic acid chemistry. And amine chemistry. We'll talk a little bit about peptides and their synthesis. And if everything goes according to plan, we'll spend maybe our last lecture talking about chapter 26 and some really cool organometallic chemistry that I want to show you. We won't have too much emphasis on this material, but there'll be one homework assignment from Saffling that's due to help reinforce that material. We're not going to need to clean for the intensity of that because we won't get a discussion section on it. All right. Well, on that note, I think what I'd like to do is to plunge right into chapter 19 carboxylic acids. So carboxylic acids are really important compounds. You encounter them literally every day. One of the simplest carboxylic acids is acetic acid. You encounter that on your salad dressing from vinegar. You get to taste your chemicals. You know that carboxylic acids are kind of tart, kind of sour, that some of them have some strong aromas to them. They're volatile. You encounter them also perhaps in the morning in your orange juice, or citric acid. Citric acid is actually a tricarboxylic acid. Citric acid has three carboxylic acid groups, two on the end of the five-part exchange, and one off of the middle along with the hydroxy group, so that's what we would call an alpha-hydroxy acid. You might have heard of alpha-hydroxy acids. Anyone? Face cream, stuff that you put on your face to go ahead, maybe you will peel or something for your skin. But you see it advertised in the cosmetic chart with alpha-hydroxy acids. Lactic acid and milk is another alpha-hydroxy acid. Due to the inductive effect, they're a little stronger than regular carboxylic acids. The amino acids are also carboxylic acids. Your chapter gives a nice coverage of them, and as I said, we'll be coming back to them in chapter 28 in the last week. So I'll just draw one of these here. I will draw the simple amino acid alanine. I used to turn alpha-hydroxy acid. Alpha means the position next to the carboxylic acid. You'll also hear amino acids refer to as alpha-amino acids, that's because the amino acids are alpha-amino acids. So carboxylic acids are important, and they're ubiquitous. And the defining feature of carboxylic acids is the carboxyl group. So we have a general structure. I'll kind of write out all of the lone pairs of electrons and all of the atoms here. In fact, let me be even more explicit. I have trouble getting in the habit. I'm so used to writing skeletal structures, but I will write all of the atoms here. So this is a carboxy group, the functional group that defines the carboxylic acid. The carboxy group is sometimes referred to as a carboxyl group. So you'll probably hear me referred to it both ways in this class. Now, you've already seen that I can write carboxylic acids in a number of ways. I wrote it as CO2H over here. So in addition to seeing structures explicitly spelled out like this with or without the carbon, you can see them written as RCO2H or RCOOH. These are all representations of the same thing. Compounds containing the carboxyl group fall into the broader family of carbonyl compounds, which includes ketones and aldehydes and so forth. So this is the broader family. Much of the reactivity that we see in the carbonyl group of the ketones and aldehydes, which we'll be talking about later, you get in the reactivity of carboxylic acids in their family members. So one of the things that I think students get awfully caught up on is this whole issue. And it's really important to be able to understand the anatomy of something. In other words, to recognize when we look at a molecule like citric acid that I just added up, oh, there's a carboxy group in the molecule. It contains a carboxy group. It is that looking at a greater level of depth. And the way I will also point out comes from drawing it, which is why I said writing out the whole word, act as we were, is so important. And yet it is so easy to lose the forest from the trees and naming molecules and just start to say, oh my God, I remember, do I alphabetize di-methyl under D for di or M for methyl? Do I put methyl before methyl because it has an ear and after because it's bigger? It's so easy to get caught up in that. And the fact that one thing goes on for pages and pages of gums lecture that it's difficult to see the forest from the trees. So I'm going to talk about what I see as the forest from the trees on the nomenclature carboxyl. You name them as the name of the alkane chopping off the E plus OIC acid. So very simple. If I have a carboxylic acid that has six carbons in it, one, two, three, four, five, six, the alkane that it would have been derived from is hexane. And so this molecule becomes hexanoic acid. The molecule that I drew on the blackboard before and said its common name is azetic acid is formally known as anethanoic acid. So I got a great question by email last night. And the question was how much do we have to know about it? Now some acids have names that are so widely used that you're going to never hear anyone referring to their binauristic anatomy. I doubt anethanoic acid would ever roll off of my tongue voluntarily or at least outside of the context of the vandectic situation because everybody calls it acid. Another one is a perfect example where just about nobody would refer to it by the common name is this guy. Now on the underpact name, what is a one-carbon? Acid one-carbon is methan. So its systematic name is methanoic acid. And yet you will invariably hear it referred to as formic acid. And it's its name from ants because ants have formic acid in their pipes. And if you distill and indeed the way it was first isolated was to put it in a place much like UCI which is loaded with ants, the first way that it isolated formic acid was to throw ants in water and steam the still out the formic acid. And since ants in Latin are formis, they ended up calling the after-tortions formic acid. And of course it's often the simplest compounds that have these historically driven common names because they were discovered so long ago. Alright. So the carboxylic acid is one of the highest ranking functional groups in naming. In other words, it ends up dictating the name of many compounds. For example, if we have a carboxylic acid that also has a hydroxy group on it, we don't name it as the carboxylic, as the alcohol, we name it as the carboxylic acid. So this is for hydroxybutanoic acid. If you have a ketone group on the chain, like so, we would call this three oxo-butanoic acid. And we would name it after the 1, 2, 3, 4 carbon chain molecule before carbon chain acid. Like so many molecules, this has a common name. That common name happens to be acetoacetic acid. If you have two carboxylic acid groups at the ends of a chain, we call it a dioy acid. Since there are two. So this six carbon chain molecule is hexane dioy acid. You're going to encounter it in the discussion section this week. So hexane dioy acid is also referred to as diphtheic acid. It's a component of nylon. Question? Yeah, sorry. Is that dioy acid or dioy acid? Di-o-wick. So it's H-E-X-A-N-E-D-I-O-C acid. D-o-wick. Pardon me, thank you. D-I-O-I-C acid. Thank you. Good catch. All right. The last sort of class that I'll just talk about in general is if you have benzene, then it's a benzoic acid. And so I'll just give you one last example. If we put a chlorine off of our benzene, this would be P-chloro-power-chlorobenzene, I would guess. Okay. I have a question. Do carboxylic acid make really good hydrogen bonds? Great, great question. They do indeed. And thank you so much for leading us into our next topic, which will be the physical properties of carboxylic acid. So carboxylic acids boil a little higher than you might expect for compounds of their size. Acetic acid is a little molecule. It just has two carbon atoms and a couple of oxygen atoms. And yet it's got a high boiling point. It has a boiling point of 118 degrees. And I borrowed this example from your textbook because I thought they did a really nice job of explaining things. So if you look at a comparison, so it's a liquid, I think we would all expect something with a boiling point of 118 degrees to be a liquid. Unless of course it were solid that might melt below 118. If you compare a molecule about the same size, let's say butane, butane is a gas. And it goes at zero. Molecules have boiling points above absolute zero because there are forces that make them stick together. But on your hand, liquid helium boils pretty darn close to absolute zero. And the only thing that helium has are Van der Waals interactions. Remember spontaneous dipole-induced dipole interactions that make the molecules stick together. But in terms of get up to hexane, to butane, of course you've got a lot more molecule and a lot more polarizability that can give rise to interaction. So butane has Van der Waals interactions holding it together. It's about the same size and yet the boiling point is a lot lower. If you go to a molecule like butanol, or let's go to propanol, for example, they get about the same size, about the same number of heavy atoms, about the same molecular weight as a seedic acid. Butanol, propanol, has a boiling point of 97 degrees, so it's lower, 97 of course these are all Celsius, so it's lower than a seedic acid. You've got Van der Waals interactions. You've got dipole-dipole interactions. In other words, you've got a dipole and the CO bond within the OH bond and that can make the molecule stick together. And you've got hydrogen bonding because the OH groups can hydrogen bond the molecules. And so, collectively those interactions bring the boiling point of propanol way above almost 100 degrees above the boiling point of butanol. And yet, not as high as a seedic acid. So hydrogen bonds are clearly worth something. How long do you think about separating them from, say, the dipole-dipole component? Well, we can look at an example of a similar molecule that doesn't have any hydrogen bonding. So we can look at propanol. Propanol, again, is about the same molecular weight. It's got the same basic number of heavy atoms for heavy atoms. It has a dipole in it and again it has an hydrogen bond. The dipole in point is 48. It's a length, just like propanol. And yet, without the hydrogen bonding, the dipole in point is about 50 degrees lower. So we have annuals of 9.9. So there's something really, really special about the hydrogen bonds in the seedic acid and in carboxylic acids in general. Carboxylic acids love the hydrogen bond together because they can form a very nice hydrogen bond really dynamic. In the hydrogen bond in dimer, you have one carboxylic acid facing another carboxylic acid. And the oxygen of one hydrogen bond to the hydrogen of the other and vice versa. And this makes the molecules stick together extra well. If you in your laboratory course ever run thin layer chromatography, TLC, like carboxylic acid, you will see that typically they streak in the TLC. By streaking, I mean that they have a spot with a tail on it, like a comet. Because at the front of the band and the TLC, as your solvent moves up the TLC, your sample is really concentrated and it's hydrogen bond moving to itself. So it doesn't hydrogen bond to the silica of the TLC plate. It moves quickly up the plate. But at the tail, as it gets more dilute, you have less hydrogen bonded dimer, less in the molecule sticking to itself, and more of it available to stick to the silica gel of the TLC plate. And so it lags, the more it lags, the more diluted it becomes, the more diluted it becomes, the more you have, the more you have, the more it lags. So TLC-wise, you see very characteristic behavior of this. You see some really interesting features spectroscopically for carboxylic acid. So for example, in the infrared spectrum, you have an OH stretch at a characteristic position. It's really, really unusual. You see this very, very characteristic band from about 3,500 to 2,500 wave numbers. It's one of the ugliest features that you'll ever see in the IR spectrum. It's very broad. And the best way I can sketch it out would look something like this. If your IR spectrum sort of starts at 4,000 wave numbers, by about 3,500, you start to see this band come up and it's sort of misshapen, and then it kind of comes down at about 2,500. So it's a very hard, hard, and spelling. It usually obscures the C8 stretches at about 3,000. And then as you come along in the carbonyl region at about 1,700 or 1,725, you'll also see the CO stretch, the carbonyl stretch. So let's say about 1725 to 17300 wave numbers. It's a really, really characteristic, just staring you in the face when you look at these. So NMR and IR spectra also have characteristic features of carboxylic acids. And a lot of this is the best way. You'll get to see some of these compounds in the lab class if you haven't already. The best way is to actually see spectra question. It's still pretty ugly. And so the question that's being asked is about concentration. And if you want it, concentrated would be say the liquid sandwich between two salt plates would be typical. Or if it's a solid in a potassium bromide pellet. And those tend to be really ugly in my experience. In solution, I haven't looked personally recently. I would think of anything you possibly, very dilute, see a little warm autumn or it should be more well-bending. So I'm not sure if that's true, but if you see an example, I'd look to see what you're reading there. It's the other thing that's interesting in the IR spectrum. Some of it depends on how big the molecule is. After all, if you've got a small carboxylic acid like butanoic acid or acetic acid, that molecule has a ton of carboxyl compared to other stuff. So when you're sandwiching a drop of acetic acid between two salt plates, there's a ton of carboxyl groups. If you had a molecule with 20 carpins in there and just one carboxyl group, you'd see a much smaller stretch for the carboxyl group. So what I'm saying here and for that spectrum is sort of characteristic of a smaller molecule. For like an amyloid molecule, like a steroid, like a cholesterol molecule, the carboxylic acid will be smaller and a little bit less obvious. But there's still you to the obvious. Good question. Other questions? Sorry, how can we differentiate a carboxylic acid from just an alcohol? Ah, great question. Carboxylic acid from just an alcohol peak. So typically an alcohol peak, and again I'll refer to one concentrated, kind of picks up at about 3500 and kind of comes down by about 3000. So this would be a typical alcohol and you'd see it more sort of centered at 3300. Whereas the carboxyl is pretty featureless. It may have some small features over here or over here. And it's just sort of this blob that encompasses the CH region of about 3000. Oh, sorry, I'm on questions like, so how can we see the CH peaks in the carboxylic acid? You may not. The question is how do we see the CH peaks? And the answer is you might not see them, but guess what? These days in organic chemistry there are so many ways to tell a molecule as CH is in it. For example, NMR spectroscopy that in general is a molecule. And in the scientific journal called Journal of Organic Chemistry, back many years ago when NMR was the primary way of describing molecules, you were supposed to describe every band in the spectrum and list like 20 or 30 peaks. Nowadays, the instructions, since there are so many good ways of looking at molecules, the instructions aren't list the main peaks as they're shooting at functional groups. These days if Johnny or Kim prepared a carboxylic acid and described it in the Journal of Organic Chemistry or in the laboratory report, they would probably say 3,500 to 2,500 wave numbers of broad peaks and 17, let's say 10 wave numbers of another peak. So you may not see them. In the NMR spectrum, you of course get to see lots and lots of hydrogen. The carboxyl hydrogen, ironically you don't always see. Generally it's about at 10 to 13 ppm. Your textbook says 10 to 12, neither knows its part. Often it's broad. Its position depends a little bit on the solvent, if you're looking at it in chloroform, if you're looking at it in dimethyl sulfoxide, and sometimes you actually won't see it. Your textbook, in a lot of ways, would never give you an example of an NMR spectrum where you didn't see the carboxylic acid or wave, but if Johnny or Kim went into the laboratory and prepared a carboxylic acid and tried to determine a carboxylic acid and took an NMR spectrum in chloroform and said, I don't see the carboxyl OH, even though it looks like a carboxylic acid, the infrared spectrum, I don't know if I have a carboxylic acid, I'd say, you know, sometimes you don't see the OH because it can be very broad due to exchange with water. Why don't you go back and run the NMR in a different solid like dimethyl sulfoxide and you try to come back and say, ah, I see it. But your textbook would never give you that much reality, or I wouldn't, because it's way beyond the scope of this book. But that's the reality. Now, the other thing is okay, what do you think about when you think about the hydrogen, the carboxyl group is electron withdrawing, in doubtful way. And so the CH that's next to a carboxylic acid generally appears at about 2 to 3 ppm. The textbook says 2 to 2.5, either is fine. If it's a methyl group, it'll be at about 2. If it's a methylene, a CH, 2 group, it'll be about 2.5. If it's a methine group, a CH group, it'll be at about 3. And if there are other electron withdrawing groups, it'll be further down fuel. The NMR spectrum, the carbon-13 NMR of carboxylic acids, your carboxyl carbon generally appears at about 170 to 180 ppm. That general region of about 170 and further down fuel is generally referred to as the carbonyl region. So generally, carbonyl compounds are generally about 170 to 220. The textbook said for carboxylic acids, 170 to 210, but they were really trying to encompass all of the carbonyl region. So generally, it'd be about 170 to 180 ppm. I'm going to write in general here. So, I'm going to write in general here. So, carboxylic acids, carboxyl groups of carboxyl groups, of carboxylic acids, is in a high oxidation state. In fact, they are the highest oxidation state of any organic compound, with the exception of things that are in the carbon dioxide oxidation state. So, if you in general have a carboxylic acid like acetic acid or hexanoic acid or benzoic acid, the oxidation state is plus three for the carbon. Informic acid, if you count your oxidation state, it's plus two. But what that immediately tells us is they're generally synthesized by oxidation reactions, because in general, a lot of organic compounds you encounter have carbon in lower oxidation states. So, alcohols, for example, depending on the substitution, will have oxidation state of if it's a primary alcohol, negative one, if it's secondary it'll be one different. And so, primary alcohols can be converted to carboxylic acids by oxidation. And you've already encountered oxidation reactions in the 51B course. So, for example, with chromium-6 reagents. Let's say EG with chromium-VI. So, what I mean is potassium dichromate and sulfuric acid, or sodium dichromate and sulfuric acid, or chromium trioxide and sulfuric acid. They're all about the same in their reactivity. There are other oxidizing agents. In general, chromium-6 is a really bad actor. It's personogenic, it's toxic. In general, organic chemists try to use safer oxidizing reagents these days, ones that are more environmentally friendly and don't generate waste. So, other sorts of oxidation systems that get used involve things like bleach, sodium hydrochloride, and various catalysts. Anyway, the general gist is there are many oxidation reactions that can make, can synthesize the carboxylic acid group. So, for example, you're also familiar with oxidative cleavage. Alkynes, ozone. That's a little bit of an oddball in some way because alkynes aren't that commonly occurring. Alkenes are a lot more common. So, I also included in the example in this week's discussion section, alkynes, and you'll see a reagent system for the oxidative cleavage of alkynes. Your textbook provides a nice review, and so you'll also see in your textbook oxidation of aromatic compounds. So, you'll see that in the next slide. With an n-zillic CH group. So, these are all things that you've encountered in your previous course. And in that case, you'll see, for example, potassium permanganate KM04 as a reagent. All right. As the name carboxylic acid implies, carboxylic acids are acidic. They're not strong acids, like sulfuric acid, like battery acid or hydroporic acid. Those acids, if you dissolve them in water, completely ionize. One molar solution of sulfuric acid is pKa, or one molar solution of hydroporic acid, is pKa of zero to ver, is pA, pardon me, zero. The ver is strong acid, and if you splash it in your eye, it's going to cause real damage. Vinegar is a weak acid. Vinegar or acetic acid is a weak acid. It's a 5% solution, which is close to one moment. If you splash vinegar in your eye, it's going to hurt, but you'll wash your eye after, and that's only to be blind or to be emergency-proof. Weak acids and strong acids, of course, react with strong bases. So for example, acidic acid reacts with hydroxide aniline to give you acetate aniline in water. And I've sort of focused here on the ions. You can't just buy or find a bottle of ions. If you go to the stock room and you say, maybe some hydroxide, they're going to say, well, I can't just give you any hydroxide. We've got to add a particular hydroxide. I can give you sodium hydroxide. I can give you calcium hydroxide. But you can't get hydroxide ions just to sit with each other without metal counteron, as they're for each other apart. And so we could write a real balanced chemical equation for, say, the acidic acid plus sodium hydroxide goes to sodium acetate, CH3, CO2, all right, with minus NH plus. So acidic chemists are not good people who are horrible about balancing equations, but now I'll be a good person and balance my equation. Sodium acetate in water. Yes? Oh, sorry. Sodium acetate should be CH3, CO2 minus. CH3, CO2 minus. Thank you. I'm going to front row every class. And I want everyone else to help out with this. Yes. Wow. So I haven't written an equilibrium there, because that reaction just lies so bloody far to the right that for all intents and purposes, if I throw sodium hydroxide, one mole of sodium hydroxide, together with a mole of acidic acid, there is no acidic acid left. I've got a mole of sodium acetate. That equilibrium lies fantastically far. Sulfuric acid has a pKa, so a way an indicator of acidity is pKa. The pKa of acidic acid is 4.76. That's typical of a weak acid. The strong acid, like sulfuric acid, is negative. Hydronium ion is negative, I believe, 1.7. In this equilibrium, water is acting as a base, or rather hydroxide is acting as a base. Water is the conjugate acid. We often compare equilibria by comparing the conjugate acid on the two sides of the equation. Water has a pKa of 15.7 acting as an acid. In other words, it's a much, much weaker acid, much, much weaker acid than acetic acid. That equilibrium lies to the way, way, way to the right. So far to the right, then we barely consider it as an equilibrium. Organic chemists often think about water and alcohols together. They're kind of in the same family. They both have hydroxyl groups. They have many similar properties. The pKa of alcohols is very similar to the pKa of water. Alcohols are about, if you want to keep one number in your head, about 17. If you can't keep one number, just say, oh, they're about the same as water. We call them both 16. So these are weaker acids. Their conjugate acid, conjugate base is RO minus or OH minus. And so if we think about why they're weaker acids, one way, one model in which to understand this is when we look at acetate anion, we can spread that negative charge around. There isn't a negative charge on one oxygen and a neutral charge on the other. So there isn't a double bond to one oxygen and a single bond to the other. It's sort of half and half. There are two resonance structures that are equivalent that together represent a more complete picture of the structure of the anion. We can say that the negative charge is stabilized by resonance. And that special stabilization that doesn't occur in hydroxide anion or in alkoxide anion makes this a weaker base, makes acetic acid a stronger acid than water or then in alcohol. Organic chemists aren't big calculators. Organic chemists are big estimators. We tend to think about things in sweeping terms. So when you're taking general chemistry, you're typically focusing on calculating in detailed positions of equivalent. When you're thinking about organic chemistry, often you're thinking about acid-base reactions and asking, what is this equilibrium like? Is it light in the middle? Does it light to the right? Does it light way to the right? Does it light way to the left? Does it light or way to the left? And that's how I like to use these days in my thinking. So when I think about equilibrium in an acid-base reaction, I sort of think about broad estimates in terms of pKa. And I think I write equations because that's not how I think, but I'll show you how I get to my thinking. So the equilibrium constant is 10 to the delta pKa. So what do I mean? I mean, if you have an acid or COO8, and its pKa is about 5, see I'm not even going to worry about extra digits here because basically I'm thinking in broad terms, carboxylic acids have pKa and 4 or 5. So I have a base like alkoxide or hydroxide, and I have an equilibrium. I've already said this equilibrium line is way, way, way to the right, and I'm so far to the right, I'm not even bothering to think about why it's where it is. So here's my equilibrium, and the pKa of my alcohol, my hydroxide, is 17. My estimate, the thing that's going on in the back of my head is oh, kEq is equal to 10 to the 17 minus 5 is 10 to the 12. That equilibrium is so far to the right that it's hardly an equilibrium. It's just there, it's just reactive. 10 to the 10th is a big number, right? It's 10 to the 1, 10 to the 2, maybe even 10 to the 5, even maybe sort of up a little bit above that, like 10 to the 8th. You can say, okay, there's kind of sort of an equilibrium, but this is way, way, way to the right, which is why I didn't even bother to think about it. So most carboxylic acids are pKa of 4 or 5. We saw it with acetic acid 4.76. Benzoic acid is a little bit worse. But sometimes you have big effects. Sometimes you have big effects that lead to inductive stabilization, it becomes a good base. And that's going to lead to a stronger acid. So as I said, typical carboxylic acid is 4 to 5, but if you take something like trifluoroacetic acid, trifluoroacetic acid has a pKa of 0.23. Johnny and Kim work with trifluoroacetic acid all the time in the laboratory. They use it as a relatively strong acid, and it's right on that equilibrium between strong meaning, reported water at all ionizing, and weak meaning, it doesn't ionize a lot. Ionizing is a lot in that group. If you get it in your eyes, there, you should worry about it. If you get it on your skin, there you should worry about it. What's going on? Those fluorines are super, super electron-induined, and we got three of them. They all have these night poles pulling negative charge away from the conjugate base, stabilizing the conjugate base. And so we get five orders of magnitude more acidic than a regular carboxylic acid. If you put fewer electron withdrawing groups, like one or two fluorines, like less acidic, if you go ahead and you move your halogens down the chain, like 4-chlorobutanoic acid versus 4-chlorobutanoic acid, out 2-chlorobutanoic acid, they're both more acidic than but 4-chlorobutanoic acid, but 4-chlorobutanoic acid, but 2-chlorobutanoic acid is a little more acidic, whereas 2-chlorobutanoic acid is a good idea, Laura. And you get the same effect, I'll give you one last example to close here. You get the same type of effects with benzoic acid, and you can think of this in terms of the reductive effects that you've learned. So benzoic acid has a pKa of 4.19. If you take parenitrobenzoic acid, you can have reductive and resonance effects pulling electron density away from the carboxyl group, and its pKa is 3.19. So you get effects there. Alright, I think that wraps it up for today.
 Monday, Wednesday, Friday, classes end up being 10-11, 11-12.  I've kind of split the hour from 10.30 to 11.30.  But honestly, if you want to try to see it other times, come on by my office.  There should be no doors usually open.  There shouldn't be an excuse I can't make to office hours.  In terms of getting a touch with me this way, patch me after class or during my office hours,  particularly for questions involving organic chemistry where there are structures involved,  it's very hard to communicate about technical matters by email and just honestly, they're too good at checking my email.  Let's see, the other thing, if you, the other people who are going to be very, very important to you in the class  are teaching assistants, Johnny Pham and Kim Lee.  And I picked two of the best graduate students from my laboratory to serve as teaching assistants.  Johnny and Kim, do you want to stand up?  So, Johnny and Kim are going to be handling the discussion sections,  and so you'll get to know them in the various discussion sections for the course.  They've set office hours on Wednesday and Monday, and they meet right in the area outside of my office.  So you'll be able to meet with them, and I posted their email addresses here.  So, the textbook for the class is the Smith Text, which you've been using.  I won't go a whole heck of a lot into it. I think it's a pretty good book.  I'm going to put emphasis on various parts in the lecture.  The break up to me, you'll get a feeling for what I think are some of the most important aspects of the book.  Some of the material, I'll sort of final directly out, but I think they have a really good way of liking things.  Some of the things I'll pull from other notes of my own, you'll get a feeling for my perspective on them.  Ultimately, what I want to be doing with them is sharing my perspective on the Smith Text,  which I really love and am passionate about.  Organic chemistry is so central to life and to all of its functions.  Johnny and Kim are both earning their PhD in organic chemistry and are working on health-related problems.  Johnny is working on how to understand his research, how to understand and control protein aggregation  with Alzheimer's disease using organic chemistry.  Kim is working on protein interaction in cancer and in HIV transmission, again, using organic chemistry.  The thing that we're going to learn in this class is central understanding all of life's processes and in terms of developing new medicines.  The textbook for the class, as I said, is pretty good by now. Probably none of you are going to be doing this,  but if you want to get the electronic, if you're coming in, say, from having been in a different quarter elsewhere  and you want to get the electronic version, that's available as well.  Now, organic chemistry classes are really only a whole piece of the picture. The biggest picture for organic chemistry is not reading a textbook.  It's not just coming to class. That's sort of the basis. But the real part is active learning.  And organic chemistry, in particular, you learn by actively processing problems.  One of my developments in this section is I can't do what I've done in the honors class.  The honors class has students get rated feedback from the GAs. It's also a much smaller class.  And it's really just so incredibly valuable. You're working and wrestling with a problem set in a deadline to have to actually work the problem in your set.  And the other thing, of course, that's wonderful is deadlines. I hate them, but I love them for myself.  I mean, it keeps me on focus. And this is, of course, one of the greatest wonders that I've ever done in the past.  It's easy to fall behind as a class. And so what I've done is the next best thing that happened with Johnny and him,  where homework is signed into individual. And that is you won't have electronic homework, who's that for the work, I know.  How many of you have used this in previous quarters? So most of you are familiar with this system.  This has been the first year I've adopted this system. I consider it to still be a work in progress.  This is the first time. There's a lot of junk out there. I've been watching for years with textbook companies coming up with their own quick multiple quick.  The first point, I think it's getting close to thinking of life-organic plans. It's not perfect. It's a little clumpier on the implementation than I'd like,  but it's a baseline. It's a starting point. On top of that, we're going to have problems that you work and present in the discussion section.  And there are homework problems which, alas, are too much sort. Have the answers key with them so you can always check yourself.  But I know, I know, I know there's this temptation when you're working problems to look at the problem, say, oh, I understand it, or I think I understand it,  then look at the answer key. And that is such a short circuiting to the learning process. And so I urge you, I beg you, if you want to master the material,  don't do that. Actually write out the answer, commit, and then go ahead and look at the answer key. And I know it's hard to have the result.  So, all right. So you have the website for the course, and let's see. So we have discussion sections for the class.  As I said, we're going to be working the problems, working problems in most of these. I've made them match up to the chapters in the course for running through chapters 19 through 25,  and then we're jumping to carbohydrate in 27, and then the last week we'll do some special topics from amino acids and from some of the chemical chemistry.  And so I've matched up the discussion sections to them. You need to be enrolled in a discussion section. It's best to go to the one you're enrolled in,  but if you can't make it to the one you're enrolled in, there are other discussion sections you can go to. It's a little confusing how I've juggled things,  because we miss Monday discussion sections. We're going to hit the ground running on Tuesday. Discussion sections in the first half of the course are going to run Tuesday to Monday,  Tuesday to Monday each week. Then at the midterm, we're going to switch. We'll have a block of discussion sections from Wednesday to Friday,  right after the midterm, which will be going over the midterm. I urge you to come to it. It's a great way to learn about things that you didn't understand.  And then for the course after the midterm, our discussion sections will be running Monday to Friday, Monday to Friday,  and if you're in the Memorial Day one, you'll just pick up one of the others. If that sounds confusing, don't worry. I've put a link here,  and you can go ahead and see the schedule for discussion sections so you never miss out. So that's just on the syllabus website.  Friday had two discussion sections that had very low enrollment, and so we closed those discussion sections. I urge you to come to the, I think it's the 12 to 1230 on Friday instead,  but if that doesn't work with your schedule, just pick another discussion section. All right. This is the first time that I've taught this particular section,  and so I've set up our schedule in advance. I think it's all going to work, but you should check the website just in case we make any changes in the scheduling.  So I've set up all of our reading assignments for the year up here, and I've set up our first homework assignment and its deadline,  and then others I've set the deadlines, but I'll be getting the problems up there. The problems should be up about a week in advance.  If you're not seeing the problems about a week in advance, send me an email, and I'll let you know if there's anything wrong with the posting.  Sorry. Like for the homework assignment, some of them say not to be submitted.  Ah, great question. So the question is, for the homework assignment, some of them say not to be submitted.  So the Sapling one supports you to submit online. I would love to be able to see your paper written out of homework.  In fact, you would make me incredibly happy if you come to my office, if you ever don't understand something, and bring me a big sheet of sloppy, messy papers with pencil scrolls with all of your efforts on the homework.  If you come to my office, bring your notes. I don't know if you don't understand. I want to be able to help you. I want to see your homework.  But as much as I would love for Johnny and Kim to be able to actually bring their homework, they can.  So the second best thing to having homework that's actually due to hand in is problems from those textbook homework assignments are going to come back to you on the quizzes.  So the quizzes, you're going to have seen all of the problems before. The quizzes are going to have problems that are taken directly from the discussion section and from the Smith-Pomer problems.  The discussion section problems won't have answers. You won't be able to get them online. So you've got to go and visit the discussion sections to see the problems and to discuss them.  Alright, homework's always a conundrum, particularly in the context of the issue of academic honesty and reading. I've really thought before you about this issue for homework because I see it as different from the exams.  My hard-to-feeling opinion on homework is I want you to learn by doing the problems. Some people like to work problems alone. Some people like to work problems in group.  My primary feeling is learning. And so I've really set up the network. If you get a problem wrong, it poachers you. You get a chance to do it over. There's just a small penalty.  So for working in groups, my philosophy is it's okay to have real peer learning to be learned in every community. What's not okay is to just be approving a person's answers and then to be mindlessly typing them in to the standpoint.  That's not learning. That's not teaching. If you're actually communicating and understanding from a peer, you're learning how to communicate. You're better reinforcing the ideas in your mind and your peer, in turn, is actually learning.  And next, the attitude for working in groups that I would see on the homework problems. Alright. So, got to come to the lecture section. You're going to miss things if you don't.  I've set up this course on video. Videos for the course will be available if you have to miss the lecture or better still, if you want to miss the lecture. You can download them. We're going to get them on YouTube.  The open courseware site produces the I. The I tunes used so there will be lots of ways to access the material for review. But come to the class.  Alright. So, quizzes. We have six quizzes. As I've said, the quizzes are going to come directly from the homework assignments and from the discussion section problems. The quizzes are on the dates that I posted here.  We don't have make up quizzes. We drop the lowest quiz. Any quiz that's missed counts as your own. I think that we drop the lowest quizzes.  Quizzes are returned through the electronic thingamajig here. I think you're all familiar with electronic exam return. Yeah. Yeah. So, you'll get your quizzes back through that.  Quizzes count for 20% of the grade. The midterm exam, which is on Tuesday, May 8th and covers chapters 19 to 22, is on. Counts for 25% of the exam.  The final exam is on June 12th and counts for 45% of the course and the homeworks count for 10% of the course.  There'll be a seating assignment chart for the midterm and for the final exam. I won't have seating assignments for the quizzes, although I appreciate it if you try to spread out and choose an empty seat without a neighbor if possible.  You do need to bring a picture ID. The UCI ID is the best thing. A driver's license would be the alternative for the midterm and for the final exam.  You'll be passing them down the aisle and the DA's will be matching your face with the ID and the exam, you know, the assigned seat. And during the exams, you need to have that.  All right. All right. Academic honesty. You all know a cheating is copying off your neighbor, getting materials in an appropriate way. Don't do it. It is fatal.  You will get a zero in the course. A note will go into your file and you will be able to go on with things that require this.  Two students in my previous class of 1051 received a failing grade for cheating. And one friend of them who wasn't an enrolled student but colluded received a note from his class. So don't do it.  Cell phones. We all have them. We all love them. We check our email on them. We get text messages. Take them away in class. Away. Off. No buzzing.  You vibrate if it doesn't distract you. I find my own distracting if it vibrates because it means, oh, there's something in my pocket that I now need to know on. Just turn it off. Don't get me cell phone.  If you don't. If you're distracted by your cell phone, I will send you out.  All right. By now you probably know about enrollment in these large classes. The professors don't handle any of that. It's done online and through the undergraduate office and there's all the contact information.  Tutoring. Best place to get help. Me, Johnny, Cam, office hours, discussion section, their office hours coming by. If you want to get some help through tutoring, there's LARP.  Chemistry also makes tutoring services available for free and they'll have information that's posted. And then I already blasted you with an email. I thought this was actually pretty cool what the chemistry department was offering.  So while they're focusing on this particular homework or that particular homework they recovered and all the topics and I feel like that's pretty good. That's important here. So anyway, let's see if there's anything else that I want to talk about.  I think that pretty much covers it. Oh yeah. I'll be giving you some software. I paid about 700 bucks for this software. It's great for visualizing molecules and they said I could give it to all my students and they said they could use it for research.  It's really cool for looking at molecules. We'll use it later on to look at sugars and understand some of your theory of chemistry. And so during one of the discussion sections, the TAs will be working with you to help teach you how to set that software.  Who has a laptop computer or portable device in the class? Good number of you. Bring those to that discussion section. That will be the week of, they will help you set up on your computer. That will be the week of April 17th through April 23rd.  Then we will remind you again. Alrighty. Well, I think that about covers it.  So, questions on the syllabus. So of course.  So our discussions are running. The questions went through the discussions starts. So we'll start on a Tuesday and run through Monday. So Tuesday, Wednesday, Thursday, Friday, Monday will be the same as the first half of the course.  Up through the midterm and then after the midterm will have three Wednesdays and midterms on a Tuesday. So Wednesday, Thursday, Friday will be the same as the first half of the course.  So the quiz schedule. The quiz is, check the syllabus I believe there on Thursday, the first half of the quarter and Tuesday the second.  Alright. Other questions? Well, I'm really enthusiastic about teaching this particular course. This is in my opinion the most exciting quarter of organic chemistry because we get to learn all the good stuff.  All the stuff. We've got to leave all this groundwork in place. You've learned about stereopenistry. You've learned about alkane, and alkene, and alcohol, and texting on our cell phone.  So you've learned about all of this incredibly, incredibly cool stuff. And now we've come to what in my opinion is the richest, the most wonderful stuff in organic chemistry.  And most of the class, seven weeks, is going to focus on carbonyl chemistry. Broadly defined.  We are going to start off with carboxylic acids. And the carboxylic acid family. We're then going to work on to aldehydes and to ketones.  Aldehydes and ketones have just a fantastically rich chemistry. They have chemistry of reactivity at the carbonyl group. They have chemistry of reactivity at the adjacent carbon.  Alphabetum saturated carbonyl compounds have chemistry of reactivity of the alkene part of the molecule. Carboxylic acids. We're going to start off.  Chapter 19 is kind of funny. It's sort of just a little book of throwaway chapter in carboxylic acids. Just the taste of it.  But carboxylic acids constitute a big and important family. And so we're going to learn about members of the family. We're going to learn about esters and amygs.  And then we're going to move on in about the eighth week of the course to talk about amines.  And then we're going to spend the ninth week of the course talking about carbohydrates, sugars.  And finally, if everything goes according to schedule in the tenth week of the class, we'll have some selected topics from chapter 28.  Chapter 28 is on amino acids. And so it's sort of a refrain of carboxylic acid chemistry. And amine chemistry. We'll talk a little bit about peptides and their synthesis.  And if everything goes according to plan, we'll spend maybe our last lecture talking about chapter 26 and some really cool organometallic chemistry that I want to show you.  We won't have too much emphasis on this material, but there'll be one homework assignment from Saffling that's due to help reinforce that material.  We're not going to need to clean for the intensity of that because we won't get a discussion section on it.  All right.  Well, on that note, I think what I'd like to do is to plunge right into chapter 19 carboxylic acids.  So carboxylic acids are really important compounds. You encounter them literally every day.  One of the simplest carboxylic acids is acetic acid.  You encounter that on your salad dressing from vinegar.  You get to taste your chemicals. You know that carboxylic acids are kind of tart, kind of sour, that some of them have some strong aromas to them.  They're volatile. You encounter them also perhaps in the morning in your orange juice,  or citric acid.  Citric acid is actually a tricarboxylic acid.  Citric acid has three carboxylic acid groups, two on the end of the five-part exchange,  and one off of the middle along with the hydroxy group, so that's what we would call an alpha-hydroxy acid.  You might have heard of alpha-hydroxy acids.  Anyone?  Face cream, stuff that you put on your face to go ahead, maybe you will peel or something for your skin.  But you see it advertised in the cosmetic chart with alpha-hydroxy acids.  Lactic acid and milk is another alpha-hydroxy acid. Due to the inductive effect, they're a little stronger than regular carboxylic acids.  The amino acids are also carboxylic acids. Your chapter gives a nice coverage of them,  and as I said, we'll be coming back to them in chapter 28 in the last week.  So I'll just draw one of these here. I will draw the simple amino acid alanine.  I used to turn alpha-hydroxy acid. Alpha means the position next to the carboxylic acid.  You'll also hear amino acids refer to as alpha-amino acids, that's because the amino acids are alpha-amino acids.  So carboxylic acids are important, and they're ubiquitous.  And the defining feature of carboxylic acids is the carboxyl group.  So we have a general structure. I'll kind of write out all of the lone pairs of electrons and all of the atoms here.  In fact, let me be even more explicit. I have trouble getting in the habit.  I'm so used to writing skeletal structures, but I will write all of the atoms here.  So this is a carboxy group, the functional group that defines the carboxylic acid.  The carboxy group is sometimes referred to as a carboxyl group.  So you'll probably hear me referred to it both ways in this class.  Now, you've already seen that I can write carboxylic acids in a number of ways.  I wrote it as CO2H over here.  So in addition to seeing structures explicitly spelled out like this with or without the carbon,  you can see them written as RCO2H or RCOOH.  These are all representations of the same thing.  Compounds containing the carboxyl group fall into the broader family of carbonyl compounds,  which includes ketones and aldehydes and so forth.  So this is the broader family.  Much of the reactivity that we see in the carbonyl group of the ketones and aldehydes,  which we'll be talking about later, you get in the reactivity of carboxylic acids  in their family members.  So one of the things that I think students get awfully caught up on is this whole issue.  And it's really important to be able to understand the anatomy of something.  In other words, to recognize when we look at a molecule like citric acid that I just added up,  oh, there's a carboxy group in the molecule.  It contains a carboxy group.  It is that looking at a greater level of depth.  And the way I will also point out comes from drawing it,  which is why I said writing out the whole word, act as we were, is so important.  And yet it is so easy to lose the forest from the trees and naming molecules  and just start to say, oh my God, I remember, do I alphabetize di-methyl under D for di or M for methyl?  Do I put methyl before methyl because it has an ear and after because it's bigger?  It's so easy to get caught up in that.  And the fact that one thing goes on for pages and pages of gums lecture  that it's difficult to see the forest from the trees.  So I'm going to talk about what I see as the forest from the trees on the nomenclature carboxyl.  You name them as the name of the alkane chopping off the E plus OIC acid.  So very simple. If I have a carboxylic acid that has six carbons in it,  one, two, three, four, five, six, the alkane that it would have been derived from is hexane.  And so this molecule becomes hexanoic acid.  The molecule that I drew on the blackboard before and said its common name is azetic acid  is formally known as anethanoic acid.  So I got a great question by email last night.  And the question was how much do we have to know about it?  Now some acids have names that are so widely used that you're going to never hear anyone referring to their binauristic anatomy.  I doubt anethanoic acid would ever roll off of my tongue voluntarily or at least outside of the context of the vandectic situation  because everybody calls it acid.  Another one is a perfect example where just about nobody would refer to it by the common name is this guy.  Now on the underpact name, what is a one-carbon?  Acid one-carbon is methan.  So its systematic name is methanoic acid.  And yet you will invariably hear it referred to as formic acid.  And it's its name from ants because ants have formic acid in their pipes.  And if you distill and indeed the way it was first isolated was to put it in a place much like UCI which is loaded with ants,  the first way that it isolated formic acid was to throw ants in water and steam the still out the formic acid.  And since ants in Latin are formis, they ended up calling the after-tortions formic acid.  And of course it's often the simplest compounds that have these historically driven common names  because they were discovered so long ago.  Alright.  So the carboxylic acid is one of the highest ranking functional groups in naming.  In other words, it ends up dictating the name of many compounds.  For example, if we have a carboxylic acid that also has a hydroxy group on it,  we don't name it as the carboxylic, as the alcohol, we name it as the carboxylic acid.  So this is for hydroxybutanoic acid.  If you have a ketone group on the chain, like so, we would call this three oxo-butanoic acid.  And we would name it after the 1, 2, 3, 4 carbon chain molecule before carbon chain acid.  Like so many molecules, this has a common name. That common name happens to be acetoacetic acid.  If you have two carboxylic acid groups at the ends of a chain, we call it a dioy acid.  Since there are two.  So this six carbon chain molecule is hexane dioy acid.  You're going to encounter it in the discussion section this week.  So hexane dioy acid is also referred to as diphtheic acid. It's a component of nylon.  Question?  Yeah, sorry. Is that dioy acid or dioy acid?  Di-o-wick. So it's H-E-X-A-N-E-D-I-O-C acid.  D-o-wick. Pardon me, thank you. D-I-O-I-C acid. Thank you.  Good catch. All right. The last sort of class that I'll just talk about in general is if you have benzene,  then it's a benzoic acid. And so I'll just give you one last example.  If we put a chlorine off of our benzene, this would be P-chloro-power-chlorobenzene, I would guess.  Okay.  I have a question.  Do carboxylic acid make really good hydrogen bonds?  Great, great question. They do indeed. And thank you so much for leading us into our next topic,  which will be the physical properties of carboxylic acid.  So carboxylic acids boil a little higher than you might expect for compounds of their size.  Acetic acid is a little molecule. It just has two carbon atoms and a couple of oxygen atoms.  And yet it's got a high boiling point. It has a boiling point of 118 degrees.  And I borrowed this example from your textbook because I thought they did a really nice job of explaining things.  So if you look at a comparison, so it's a liquid, I think we would all expect something with a boiling point of 118 degrees to be a liquid.  Unless of course it were solid that might melt below 118.  If you compare a molecule about the same size, let's say butane, butane is a gas.  And it goes at zero.  Molecules have boiling points above absolute zero because there are forces that make them stick together.  But on your hand, liquid helium boils pretty darn close to absolute zero.  And the only thing that helium has are Van der Waals interactions.  Remember spontaneous dipole-induced dipole interactions that make the molecules stick together.  But in terms of get up to hexane, to butane, of course you've got a lot more molecule and a lot more polarizability that can give rise to interaction.  So butane has Van der Waals interactions holding it together.  It's about the same size and yet the boiling point is a lot lower.  If you go to a molecule like butanol, or let's go to propanol, for example,  they get about the same size, about the same number of heavy atoms, about the same molecular weight as a seedic acid.  Butanol, propanol, has a boiling point of 97 degrees, so it's lower, 97 of course these are all Celsius,  so it's lower than a seedic acid.  You've got Van der Waals interactions.  You've got dipole-dipole interactions.  In other words, you've got a dipole and the CO bond within the OH bond and that can make the molecule stick together.  And you've got hydrogen bonding because the OH groups can hydrogen bond the molecules.  And so, collectively those interactions bring the boiling point of propanol way above almost 100 degrees above the boiling point of butanol.  And yet, not as high as a seedic acid.  So hydrogen bonds are clearly worth something.  How long do you think about separating them from, say, the dipole-dipole component?  Well, we can look at an example of a similar molecule that doesn't have any hydrogen bonding.  So we can look at propanol.  Propanol, again, is about the same molecular weight.  It's got the same basic number of heavy atoms for heavy atoms.  It has a dipole in it and again it has an hydrogen bond.  The dipole in point is 48. It's a length, just like propanol.  And yet, without the hydrogen bonding, the dipole in point is about 50 degrees lower.  So we have annuals of 9.9.  So there's something really, really special about the hydrogen bonds in the seedic acid and in carboxylic acids in general.  Carboxylic acids love the hydrogen bond together because they can form a very nice hydrogen bond really dynamic.  In the hydrogen bond in dimer, you have one carboxylic acid facing another carboxylic acid.  And the oxygen of one hydrogen bond to the hydrogen of the other and vice versa.  And this makes the molecules stick together extra well.  If you in your laboratory course ever run thin layer chromatography, TLC, like carboxylic acid, you will see that typically they streak in the TLC.  By streaking, I mean that they have a spot with a tail on it, like a comet.  Because at the front of the band and the TLC, as your solvent moves up the TLC, your sample is really concentrated and it's hydrogen bond moving to itself.  So it doesn't hydrogen bond to the silica of the TLC plate. It moves quickly up the plate.  But at the tail, as it gets more dilute, you have less hydrogen bonded dimer, less in the molecule sticking to itself, and more of it available to stick to the silica gel of the TLC plate.  And so it lags, the more it lags, the more diluted it becomes, the more diluted it becomes, the more you have, the more you have, the more it lags.  So TLC-wise, you see very characteristic behavior of this.  You see some really interesting features spectroscopically for carboxylic acid.  So for example, in the infrared spectrum, you have an OH stretch at a characteristic position.  It's really, really unusual.  You see this very, very characteristic band from about 3,500 to 2,500 wave numbers.  It's one of the ugliest features that you'll ever see in the IR spectrum.  It's very broad. And the best way I can sketch it out would look something like this.  If your IR spectrum sort of starts at 4,000 wave numbers, by about 3,500, you start to see this band come up and it's sort of misshapen, and then it kind of comes down at about 2,500.  So it's a very hard, hard, and spelling.  It usually obscures the C8 stretches at about 3,000.  And then as you come along in the carbonyl region at about 1,700 or 1,725, you'll also see the CO stretch, the carbonyl stretch.  So let's say about 1725 to 17300 wave numbers.  It's a really, really characteristic, just staring you in the face when you look at these.  So NMR and IR spectra also have characteristic features of carboxylic acids.  And a lot of this is the best way. You'll get to see some of these compounds in the lab class if you haven't already.  The best way is to actually see spectra question.  It's still pretty ugly.  And so the question that's being asked is about concentration.  And if you want it, concentrated would be say the liquid sandwich between two salt plates would be typical.  Or if it's a solid in a potassium bromide pellet.  And those tend to be really ugly in my experience.  In solution, I haven't looked personally recently.  I would think of anything you possibly, very dilute, see a little warm autumn or it should be more well-bending.  So I'm not sure if that's true, but if you see an example, I'd look to see what you're reading there.  It's the other thing that's interesting in the IR spectrum.  Some of it depends on how big the molecule is.  After all, if you've got a small carboxylic acid like butanoic acid or acetic acid, that molecule has a ton of carboxyl compared to other stuff.  So when you're sandwiching a drop of acetic acid between two salt plates, there's a ton of carboxyl groups.  If you had a molecule with 20 carpins in there and just one carboxyl group, you'd see a much smaller stretch for the carboxyl group.  So what I'm saying here and for that spectrum is sort of characteristic of a smaller molecule.  For like an amyloid molecule, like a steroid, like a cholesterol molecule, the carboxylic acid will be smaller and a little bit less obvious.  But there's still you to the obvious.  Good question.  Other questions?  Sorry, how can we differentiate a carboxylic acid from just an alcohol?  Ah, great question.  Carboxylic acid from just an alcohol peak.  So typically an alcohol peak, and again I'll refer to one concentrated,  kind of picks up at about 3500 and kind of comes down by about 3000.  So this would be a typical alcohol and you'd see it more sort of centered at 3300.  Whereas the carboxyl is pretty featureless.  It may have some small features over here or over here.  And it's just sort of this blob that encompasses the CH region of about 3000.  Oh, sorry, I'm on questions like, so how can we see the CH peaks in the carboxylic acid?  You may not.  The question is how do we see the CH peaks?  And the answer is you might not see them, but guess what?  These days in organic chemistry there are so many ways to tell a molecule as CH is in it.  For example, NMR spectroscopy that in general is a molecule.  And in the scientific journal called Journal of Organic Chemistry,  back many years ago when NMR was the primary way of describing molecules,  you were supposed to describe every band in the spectrum and list like 20 or 30 peaks.  Nowadays, the instructions, since there are so many good ways of looking at molecules,  the instructions aren't list the main peaks as they're shooting at functional groups.  These days if Johnny or Kim prepared a carboxylic acid and described it in the Journal of Organic Chemistry  or in the laboratory report, they would probably say 3,500 to 2,500 wave numbers of broad peaks  and 17, let's say 10 wave numbers of another peak.  So you may not see them.  In the NMR spectrum, you of course get to see lots and lots of hydrogen.  The carboxyl hydrogen, ironically you don't always see.  Generally it's about at 10 to 13 ppm.  Your textbook says 10 to 12, neither knows its part.  Often it's broad. Its position depends a little bit on the solvent,  if you're looking at it in chloroform, if you're looking at it in dimethyl sulfoxide,  and sometimes you actually won't see it.  Your textbook, in a lot of ways, would never give you an example of an NMR spectrum  where you didn't see the carboxylic acid or wave,  but if Johnny or Kim went into the laboratory and prepared a carboxylic acid  and tried to determine a carboxylic acid and took an NMR spectrum in chloroform  and said, I don't see the carboxyl OH, even though it looks like a carboxylic acid,  the infrared spectrum, I don't know if I have a carboxylic acid,  I'd say, you know, sometimes you don't see the OH because it can be very broad  due to exchange with water. Why don't you go back and run the NMR in a different solid  like dimethyl sulfoxide and you try to come back and say, ah, I see it.  But your textbook would never give you that much reality, or I wouldn't,  because it's way beyond the scope of this book.  But that's the reality.  Now, the other thing is okay, what do you think about when you think about the hydrogen,  the carboxyl group is electron withdrawing, in doubtful way.  And so the CH that's next to a carboxylic acid generally appears at about 2 to 3 ppm.  The textbook says 2 to 2.5, either is fine.  If it's a methyl group, it'll be at about 2.  If it's a methylene, a CH, 2 group, it'll be about 2.5.  If it's a methine group, a CH group, it'll be at about 3.  And if there are other electron withdrawing groups, it'll be further down fuel.  The NMR spectrum, the carbon-13 NMR of carboxylic acids,  your carboxyl carbon generally appears at about 170 to 180 ppm.  That general region of about 170 and further down fuel is generally referred to as the carbonyl region.  So generally, carbonyl compounds are generally about 170 to 220.  The textbook said for carboxylic acids, 170 to 210,  but they were really trying to encompass all of the carbonyl region.  So generally, it'd be about 170 to 180 ppm.  I'm going to write in general here.  So, I'm going to write in general here.  So, carboxylic acids, carboxyl groups of carboxyl groups,  of carboxylic acids, is in a high oxidation state.  In fact, they are the highest oxidation state of any organic compound,  with the exception of things that are in the carbon dioxide oxidation state.  So, if you in general have a carboxylic acid like acetic acid or hexanoic acid or benzoic acid,  the oxidation state is plus three for the carbon.  Informic acid, if you count your oxidation state, it's plus two.  But what that immediately tells us is they're generally synthesized by oxidation reactions,  because in general, a lot of organic compounds you encounter have carbon in lower oxidation states.  So, alcohols, for example, depending on the substitution,  will have oxidation state of if it's a primary alcohol, negative one,  if it's secondary it'll be one different.  And so, primary alcohols can be converted to carboxylic acids by oxidation.  And you've already encountered oxidation reactions in the 51B course.  So, for example, with chromium-6 reagents.  Let's say EG with chromium-VI.  So, what I mean is potassium dichromate and sulfuric acid,  or sodium dichromate and sulfuric acid, or chromium trioxide and sulfuric acid.  They're all about the same in their reactivity.  There are other oxidizing agents.  In general, chromium-6 is a really bad actor.  It's personogenic, it's toxic.  In general, organic chemists try to use safer oxidizing reagents these days,  ones that are more environmentally friendly and don't generate waste.  So, other sorts of oxidation systems that get used involve things like bleach,  sodium hydrochloride, and various catalysts.  Anyway, the general gist is there are many oxidation reactions  that can make, can synthesize the carboxylic acid group.  So, for example, you're also familiar with oxidative cleavage.  Alkynes, ozone.  That's a little bit of an oddball in some way  because alkynes aren't that commonly occurring.  Alkenes are a lot more common.  So, I also included in the example in this week's discussion section,  alkynes, and you'll see a reagent system for the oxidative cleavage of alkynes.  Your textbook provides a nice review,  and so you'll also see in your textbook oxidation of aromatic compounds.  So, you'll see that in the next slide.  With an n-zillic CH group.  So, these are all things that you've encountered in your previous course.  And in that case, you'll see, for example, potassium permanganate KM04 as a reagent.  All right.  As the name carboxylic acid implies, carboxylic acids are acidic.  They're not strong acids, like sulfuric acid, like battery acid or hydroporic acid.  Those acids, if you dissolve them in water, completely ionize.  One molar solution of sulfuric acid is pKa, or one molar solution of hydroporic acid,  is pKa of zero to ver, is pA, pardon me, zero.  The ver is strong acid, and if you splash it in your eye, it's going to cause real damage.  Vinegar is a weak acid.  Vinegar or acetic acid is a weak acid.  It's a 5% solution, which is close to one moment.  If you splash vinegar in your eye, it's going to hurt, but you'll wash your eye after,  and that's only to be blind or to be emergency-proof.  Weak acids and strong acids, of course, react with strong bases.  So for example, acidic acid reacts with hydroxide aniline to give you acetate aniline in water.  And I've sort of focused here on the ions.  You can't just buy or find a bottle of ions.  If you go to the stock room and you say, maybe some hydroxide, they're going to say,  well, I can't just give you any hydroxide.  We've got to add a particular hydroxide.  I can give you sodium hydroxide.  I can give you calcium hydroxide.  But you can't get hydroxide ions just to sit with each other without metal counteron,  as they're for each other apart.  And so we could write a real balanced chemical equation for, say,  the acidic acid plus sodium hydroxide goes to sodium acetate, CH3, CO2, all right,  with minus NH plus.  So acidic chemists are not good people who are horrible about balancing equations,  but now I'll be a good person and balance my equation.  Sodium acetate in water.  Yes?  Oh, sorry.  Sodium acetate should be CH3, CO2 minus.  CH3, CO2 minus.  Thank you.  I'm going to front row every class.  And I want everyone else to help out with this.  Yes.  Wow.  So I haven't written an equilibrium there,  because that reaction just lies so bloody far to the right  that for all intents and purposes, if I throw sodium hydroxide, one mole of sodium hydroxide,  together with a mole of acidic acid, there is no acidic acid left.  I've got a mole of sodium acetate.  That equilibrium lies fantastically far.  Sulfuric acid has a pKa, so a way an indicator of acidity is pKa.  The pKa of acidic acid is 4.76.  That's typical of a weak acid.  The strong acid, like sulfuric acid, is negative.  Hydronium ion is negative, I believe, 1.7.  In this equilibrium, water is acting as a base, or rather hydroxide is acting as a base.  Water is the conjugate acid.  We often compare equilibria by comparing the conjugate acid on the two sides of the equation.  Water has a pKa of 15.7 acting as an acid.  In other words, it's a much, much weaker acid, much, much weaker acid than acetic acid.  That equilibrium lies to the way, way, way to the right.  So far to the right, then we barely consider it as an equilibrium.  Organic chemists often think about water and alcohols together.  They're kind of in the same family.  They both have hydroxyl groups.  They have many similar properties.  The pKa of alcohols is very similar to the pKa of water.  Alcohols are about, if you want to keep one number in your head, about 17.  If you can't keep one number, just say, oh, they're about the same as water.  We call them both 16.  So these are weaker acids.  Their conjugate acid, conjugate base is RO minus or OH minus.  And so if we think about why they're weaker acids, one way, one model in which to understand this  is when we look at acetate anion, we can spread that negative charge around.  There isn't a negative charge on one oxygen and a neutral charge on the other.  So there isn't a double bond to one oxygen and a single bond to the other.  It's sort of half and half.  There are two resonance structures that are equivalent that together represent a more complete picture  of the structure of the anion.  We can say that the negative charge is stabilized by resonance.  And that special stabilization that doesn't occur in hydroxide anion or in alkoxide anion  makes this a weaker base, makes acetic acid a stronger acid than water or then in alcohol.  Organic chemists aren't big calculators.  Organic chemists are big estimators.  We tend to think about things in sweeping terms.  So when you're taking general chemistry, you're typically focusing on calculating in detailed positions of equivalent.  When you're thinking about organic chemistry, often you're thinking about acid-base reactions and asking,  what is this equilibrium like?  Is it light in the middle? Does it light to the right? Does it light way to the right?  Does it light way to the left? Does it light or way to the left?  And that's how I like to use these days in my thinking.  So when I think about equilibrium in an acid-base reaction,  I sort of think about broad estimates in terms of pKa.  And I think I write equations because that's not how I think,  but I'll show you how I get to my thinking.  So the equilibrium constant is 10 to the delta pKa.  So what do I mean? I mean, if you have an acid or COO8, and its pKa is about 5,  see I'm not even going to worry about extra digits here because basically I'm thinking in broad terms,  carboxylic acids have pKa and 4 or 5.  So I have a base like alkoxide or hydroxide, and I have an equilibrium.  I've already said this equilibrium line is way, way, way to the right,  and I'm so far to the right, I'm not even bothering to think about why it's where it is.  So here's my equilibrium, and the pKa of my alcohol, my hydroxide, is 17.  My estimate, the thing that's going on in the back of my head is oh,  kEq is equal to 10 to the 17 minus 5 is 10 to the 12.  That equilibrium is so far to the right that it's hardly an equilibrium.  It's just there, it's just reactive.  10 to the 10th is a big number, right?  It's 10 to the 1, 10 to the 2, maybe even 10 to the 5,  even maybe sort of up a little bit above that, like 10 to the 8th.  You can say, okay, there's kind of sort of an equilibrium,  but this is way, way, way to the right, which is why I didn't even bother to think about it.  So most carboxylic acids are pKa of 4 or 5.  We saw it with acetic acid 4.76.  Benzoic acid is a little bit worse.  But sometimes you have big effects.  Sometimes you have big effects that lead to inductive stabilization,  it becomes a good base.  And that's going to lead to a stronger acid.  So as I said, typical carboxylic acid is 4 to 5,  but if you take something like trifluoroacetic acid,  trifluoroacetic acid has a pKa of 0.23.  Johnny and Kim work with trifluoroacetic acid all the time in the laboratory.  They use it as a relatively strong acid,  and it's right on that equilibrium between strong meaning,  reported water at all ionizing, and weak meaning, it doesn't ionize a lot.  Ionizing is a lot in that group.  If you get it in your eyes, there, you should worry about it.  If you get it on your skin, there you should worry about it.  What's going on?  Those fluorines are super, super electron-induined,  and we got three of them.  They all have these night poles pulling negative charge away from the conjugate base,  stabilizing the conjugate base.  And so we get five orders of magnitude more acidic than a regular carboxylic acid.  If you put fewer electron withdrawing groups, like one or two fluorines,  like less acidic, if you go ahead and you move your halogens down the chain,  like 4-chlorobutanoic acid versus 4-chlorobutanoic acid,  out 2-chlorobutanoic acid, they're both more acidic than but 4-chlorobutanoic acid,  but 4-chlorobutanoic acid, but 2-chlorobutanoic acid is a little more acidic,  whereas 2-chlorobutanoic acid is a good idea, Laura.  And you get the same effect, I'll give you one last example to close here.  You get the same type of effects with benzoic acid,  and you can think of this in terms of the reductive effects that you've learned.  So benzoic acid has a pKa of 4.19.  If you take parenitrobenzoic acid, you can have reductive and resonance effects  pulling electron density away from the carboxyl group,  and its pKa is 3.19.  So you get effects there.  Alright, I think that wraps it up for today.
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