Functional Groups: Study with Video Lessons, Practice Problems & Examples

Understanding functional groups is crucial in organic chemistry, as they categorize molecules based on their reactivity and properties. Key groups include hydrocarbons (alkanes, alkenes, alkynes), alcohols (ROH), amines (RNH₂), and carbonyls (C=O). The presence of carbonyls can transform alcohols into carboxylic acids (COOH) and amines into amides (C=O-NH₂). Additionally, ketones and aldehydes are differentiated by their structure, with ketones being internal and aldehydes being terminal. Recognizing these groups and their degrees (primary, secondary, tertiary) is essential for mastering organic reactions.

Why we need functional groups.

All right guys, so in the next few videos, I want to go over probably the most important concept of this chapter, which is recognizing functional groups. Now I know that you've all heard of this before, that you're going to have to memorize some stuff, you're going to have to memorize what some molecules look like. Hopefully, a few of you guys know some of these names from gen chem, but regardless, it's going to be fine. I'm going to give you guys enough practice so that by the end of today, you're going to feel pretty confident with these groups. Alright? So let's go ahead and get started.

So what is the entire concept of functional groups? It turns out that before functional groups were categorized, what was happening is that scientists were literally just finding out new molecules and naming them after whatever they wanted. So they'd name them after their cat, and they'd name them after their girlfriend. They break up with their girlfriend and then it doesn't even make sense anymore. And it was terrible. Basically, they had these entire books of millions of molecules that just had these random names. And you can imagine that if you hate chemistry now or if you think it's challenging, back then it even sucked way worse. So they decided, okay, in the early 1900s, let's actually make groups out of this. Let's figure out what these molecules do. Let's figure out if they do similar things so that we can group them together into similar sets of molecules. So now instead of me teaching you like a thousand different names, I'm only going to teach you like 10, 14, something like that. Depending on how many you need to know for your book, that's how many I'm going to teach you. Alright? So isn't that a lot better? You guys ready to start? Cool.

So what we group them into is groups of similar functionality. So go ahead and write that down. That just means we group them into what they do. Okay? So there are certain types of molecules that they just all do the same thing or they all react in very similar ways and that's how we group them.

Recognizing different types of hydrocarbons.

Let's go ahead and start off with hydrocarbons. Okay? We've talked about hydrocarbons before, and these would be your single bonds, double bonds, and triple bonds. Okay? There's actually more types of hydrocarbons than that, but these are the ones I want to focus on right now. Okay? So, we've been calling them single, double, triple. Now what I want you guys to refer to them as is alkanes, alkenes, and alkynes. The reason is that a double bond could exist between lots of different atoms. It could be a nitrogen-nitrogen double bond. That's not the same. So if you have a carbon-carbon double bond, you should be more specific, and you should say that is an alkene. Okay? So you can tell all that's changing is really one letter, a, e, y. Okay? So as you get further in the alphabet, you're adding more bonds. Not too bad.

So I want to just say a few things about carbon structures before we get into a lot of functional groups because if you understand the carbon structures really well, the others are going to be easy. First of all, it turns out that all carbon groups, regardless of their size, can be symbolized using what's called an R group. Okay? This is something that we use every single day in organic chemistry (Orgo). All it means is this: your R group means that you have a particular part of the molecule that you're focusing on. And everything else that you don't really care about, especially if this is a big molecule, you're just going to say that's an R. Okay? That just means it's a carbon group that could be a 100 carbons long. I don't care about that part of the molecule. I'm just going to write an R instead. Cool? We use that literally every single day in Orgo.

Alright? When an alkane is attached to a greater carbon chain, it's given a -yl suffix. Okay? So that means that an alkane, if it's a branch off of a bigger chain, actually becomes an alkyl. Okay? So here I've shown you an example where I have a 6-carbon chain with a one-carbon branch coming off of it. The biggest chain is going to be referred to as the alkane, whereas the smaller branch is going to be referred to as the alkyl. Okay? So that's something to keep in mind, you put that -yl whenever it's a branch. Okay?

How to assign degrees to carbons and hydrogens.

So then, lastly, we have to figure out giving degrees for carbons and hydrogens. Okay? And degrees just have to do with how many other things are attached to my object or to my target. Okay? So the carbon here is given a degree based on how many other carbons they are attached to. Okay? So what I do here is I say that not all carbons are the same. I care I'm going to differentiate my carbons based on how many other carbons they're attached to. Okay. So I'm going to show you an example of that in a second. So basically, the words that we use for that are primary, secondary, tertiary, and quaternary or these little degree symbols. All that means is it tells you how many other carbons are directly attached to that carbon. Okay? Then hydrogens, because hydrogens always have one bond, remember that hydrogens are only happy with 1, whereas carbons can have a lot of different they can have they always have 4 bonds, but they could be bonded to other things besides carbon. Okay? So hydrogens are just going to possess the same degree as the carbon that they're attached to. So that means is if I have a tertiary carbon, that means it's attached to 3 other carbons, the hydrogen that's on that tertiary carbon would be called a tertiary hydrogen as well because it's a hydrogen of a tertiary carbon. Does that make sense? So what I want us to do, I know that's kind of a lot to take in, I have these 5 circles. I want you guys to identify one at a time what types of degrees of hydrogens and carbons we're dealing with in this molecule. That's going to help a lot for the next page of functional groups.

Determine the degree of the indicated carbons and hydrogens.

So for example, let's go ahead and start off with this. Actually, you know what? Let's not start off with this. Let's start off with carbon. Let's start off with this carbon. What type of carbon is that? The answer is that it's a primary carbon. Why is that? Because it's only attached to one other atom and that's a carbon. And actually, I kind of said that wrong. It's only attached to one other carbon. That's the biggest thing. Okay? So let's move on to this H right there. What type of H is that? So this H is what we call a tertiary hydrogen. Okay? The reason is that the hydrogen is attached to a carbon, and I get the degree from the carbon it's attached to. And that carbon is attached to 3 other carbons. 1, 2, 3. Okay? So that means that that would be a tertiary hydrogen because it's on a tertiary carbon. Alright, let's move on. How about this bottom carbon down there? What would that be? So this would be a secondary carbon. Okay? Why? Because it's attached to 2 other carbon groups. Okay. What about this carbon right there? That would be what we call a quaternary carbon. Quaternary carbon means that all 4 of its bonds are single bonds to carbon. Cool? And then finally, what about this last one that I wanted to start with? This would be a primary hydrogen. Okay? Why primary? Because it's attached to a carbon that is attached to only one other carbon. See how that works? It's a little bit tricky. I can tell a lot of you guys thought that was going to be a quaternary hydrogen. But that is not a quaternary because it's not directly coming off of the quaternary carbon. Okay? It's a primary because it's coming off a carbon, that red one, that is only attached to one other carbon. Okay. Does that make sense? So it turns out that as we learn more functional groups, I'm going to teach you that as we name degrees for them, some of them are going to be named as hydrogens, meaning that some of them are going to have the same degree as if they were hydrogens. And some of them are going to have the same degree that they would as if they were carbons. And it's important for you guys to remember that distinction. That is one of the things that tricks people the most in functional groups. And I'm going to teach it to you, but I'm just giving you a heads-up. You need to think in terms of hydrogens and carbons so that the other functional groups will make sense to you. Alright? So with that said, let's go ahead and move on to the next page.

Recognizing alkyl halides.

So our next functional group is the alkyl halide, and the alkyl halide really tells you what it is right at the beginning. "Alkyl" has to do with carbon, so that would be an R. Remember that I said R can be used for any carbon group. And "halide" is a halogen. So remember that the letter that we use for halogen is X. So the abbreviation for an alkyl halide is RX. Anytime you see RX, we're talking about an alkyl halide. Okay? So like I say, right here, it's any R group that's directly attached to a halogen, alkyl halide. This is a very important functional group for Organic Chemistry 1 especially.

And, the degree of the alkyl halide, because remember I told you we were talking about degrees here, is going to be determined in the same way as a hydrogen. Okay? So remember how do we determine degrees with hydrogen? We would look at the carbon it's attached to and say how many other carbons it is attached to. Okay? So here I have 3 different alkyl halides for you. You can tell these are all carbon groups. I'm going to call this one A, B, and C. These are all halogens directly attached to R. And now what I want you guys to do is tell me if they're primary, secondary, or tertiary. Okay? So go ahead and look at the first one. Tell me, what do you guys think?

Assigning Degrees to Alkyl Halides

So the way we determine this is by looking at the carbon it's attached to and asking, "How many other carbons is it attached to?" One. So this is going to be a primary alkyl halide. Okay? So now let's look at the second one. What kind of alkyl halide is that? That's going to be a tertiary alkyl halide. Why? Because I look at the carbon it's attached to and I say how many other carbons is it attached to? One, two, three; tertiary. Okay? Lastly, we have another example. Go ahead and figure out which one that is. So this one would be a secondary alkyl halide. Okay? The reason is that my Bromine is attached to a carbon that has three bonds, but only two of them are to carbons. That was the thing that might have gotten you a little bit tripped up. Maybe you said tertiary because you forgot that this is a hydrogen. Hydrogens don't count. All I look at is how many other carbons that carbon is attached to. See? So this is actually not that hard. Once you learn how to do it for hydrogens, alkyl halides are the same exact thing. Now what's cool is that by naming the degree, we actually group these together in terms of their functionality. It turns out that primary alkyl halides react in a much different way from tertiary alkyl halides. And by grouping them like this, we can have very predictable reactions that we can run based on saying, "Okay, we want a primary here, we want a tertiary there," it's going to change it.

How to recognize alcohols, amines and ethers.

So for the next 6 functional groups, I want to clarify something. Have you guys heard the word carbonyl? Maybe your professor calls it carbonyl. That's totally fine. However you want to say it, that's fine. In fact, you're probably going to notice this semester that I say some things very differently from the way your professor says them. Maybe because your professor speaks a different language primarily, or just because people have different ways of saying these molecules. But, I'm just going to say carbonyl. Carbonyl looks like this: it's a C double bond O. And a carbonyl is not a functional group. It is only a component of many functional groups. So if I say the word carbonyl, it doesn't mean that that's a functional group; it just means that it's part of the functional group. I'm going to talk first about functional groups without carbonyls and then we're going to add some carbonyls and see how that changes them.

The third functional group we're going to talk about today is alcohols. Alcohols are defined as ROH, any carbon group that's attached to an OH. There are lots of different alcohols, but the important thing to know is that the way you name the degree on them is the same as with hydrogens. So now we know that alkyl halides and alcohols are both named exactly the same in terms of degrees. Here I have an alcohol for you—please don't try to drink this alcohol. It would probably kill you. The only alcohol that's safe for drinking is ethanol. Even if you remove one carbon to make it methanol, it's toxic. Like, 50 grams of that and you're dead. So, they're not all fun and games. We actually use these in the lab a lot. What type of alcohol would this be, though? What do you guys think? So it's attached to one carbon. Remember that we say you always look at the carbon that carbon is attached to. That carbon is attached to only 1 carbon. This is the same as hydrogen, so this is going to be a primary alcohol.

Then let's talk about the next functional group, amines. Amines work in a way that they actually have carbon groups directly attached to the N. There are a lot of different types of amines you could have. One of the most common would just be having NH₃. But if you add R groups to it, that's also an amine. So if I had RNH₂, that is also an amine. If I switched out hydrogens for R's, that would still be an amine. So let's say that I had R₂NH. That just means I'm replacing one of the H's with an R. And then finally, I could even have R₃N. All of these would be types of amines. As long as it's basically a carbon group, carbons or hydrogens attached to a nitrogen, it would be an amine. The degree of the amine is actually determined the same way as with carbon. So in this case, what type of amine would this be, this ring structure? It would be a secondary amine because the N is directly attached to 1, 2 carbons. That's a huge distinction.

Finally, we have ether. Ether is abbreviated ROR. An easy way that I always remembered it is "I'm an ether. Roar." That was awkward, right? So anyway, I'm an ether, you're scary, blow up. Ethers actually do blow up. So maybe that helps you remember. All it is, is an oxygen between 2 carbon groups. Honestly, we don't need to name degrees for these because there's only one type. Just remember ROR, and you're good to go.

How to recognize carboxylic acids, amides and esters.

Now what I want to do is I want to add carbonyls next to all of these and see how that changes them. So I'm going to add a carbonyl to my alcohol, amine, and I'm going to add a carbonyl to my ether and I'm going to show you guys how that changes the functional group. So if I add a carbonyl to my alcohol, that means what it's going to look like is now C=O with an OH next to it. Do you guys see that? So basically, I'm taking the OH from here and I'm just adding it next to my carbonyl. Alright? It turns out that this is going to react way differently from a regular alcohol because of that carbonyl, and we're actually going to find out a lot more about that in the acids and bases chapter. Okay? So what that means is that, this is going to turn into what's called an acid. This is the main acid of organic chemistry. So most of the acids that we deal with, a lot of them are carboxylic acids. And what I'm going to do for these is I'm also going to show you guys the condensed form of writing it because this is very common. So the way that it's written is as COOH. So if you see COOH, that's to do with carboxylic acid. Another way that it's written is COO2H. These are condensed abbreviations that confuse a lot of students, so it's important that you guys keep in your memory. This is the memorization part. It's important that you guys memorize that COOH is a carboxylic acid. It makes sense just by looking at it, but still, you need to make sure you know it.

Then we've got, so basically, alcohol plus a carbonyl, you get a carboxylic acid. Then let's do amine plus a carbonyl. Well, in this case, what I would get is I would get my carbonyl and then I would add NH2 next to it. Okay? So I'm just taking my amine from here and I'm adding it here. Alright? Well, the condensed formula for this is going to be CONH2 or whatever, however many H's that nitrogen has. And this is going to go from being an amine to what we call either you could call it an amide or amide. Both I've heard both pronunciations several times from different professors. I say amide, but there will be some ways, sometimes I'll even say amide. It just depends on what's in front of it. Sometimes if the name is really long, it sounds better to say amide. Alright. So whatever. I'm just trying to say don't be strict about the pronunciation, just be strict about knowing what it is. So that's kind of easy. Notice that I go from amine, add a carbonyl and it goes to an amide. Easy. Okay? The degree of the amide is determined the same way as a carbon. Okay? So if I gave you the following amide, okay, this is actually going to be, yeah, I'll give you that amide. This is actually what's called a cyclic amide and later on in Orgo 2, we're going to learn that these are very important. It gets the name of a lactam. So now I'm totally just jumping ahead just to make this interesting. Okay? You do not need to know about lactams yet. But I just want you guys to know that a lactam is a type of amide and what's the degree of it? What would be the degree of this amide? It would also be a secondary amide. So you could call it a lactam or you could call it a secondary amide. Why? Because this nitrogen here is attached to 2 carbon groups. See how that works? So it's just the same as we were using for the amine and also the same as we were using for carbon. Cool.

And then we've got this last one. I'll try to move out of the way a little bit. So we've got ester. Ester is what forms when you add a carbonyl, and then you just take the OR from the ether group. So isn't that cool? We get when you take an amine, add a carbonyl, turns into an amide. Ether plus a carbonyl turns into an ester. So these names are very similar, and that's one of the ways that helps to remember that you can just say, hey, add a carbonyl and it becomes the one that sounds like it. So in ester, the functional group or the condensed formula is going to be COOR. Anytime you see COOR, that is an ester. There's nothing else that you really need to know about this. Oh, also it could be CO2R. But other than that, I just want you to be able to recognize these.

The difference between aldehydes and ketones.

So now let's talk about strict carbonyl groups. These are going to be groups, specifically carbonyls, C=O, that do not have oxygens, nitrogens next to them, or stuff like that. All they have is carbons. Okay? And in that case, it's still not appropriate to call them carbonyl. Instead, we're going to use the words or the names ketone and aldehyde. Okay? So what I'm going to do here is I'm going to give you guys the explanation of the difference between them because a lot of students get stuck on what's a ketone and what's an aldehyde. Alright? So I'm just going to show you guys really quick. A ketone is going to be a carbonyl that has 2 R groups on both sides. Okay? Whereas an aldehyde is going to have 1 or more H's on one of the sides. Okay? So right there, there's the difference. An aldehyde is going to have an H, whereas a ketone will never have an H directly coming off of the carbonyl. Okay? But another way that I like to think about these, because I think it helps, is if you're looking just at a structure like I have right here, just a really big structure, another way that I would think of it is that a ketone is an internal carbonyl group, whereas an aldehyde is a terminal carbonyl group. Now, what are these words internal and terminal? They're location words. They're actually words that we use a lot in Orgo (Organic Chemistry). It means it's something in the middle of a chain or of a ring or something at the very end. Okay? And you can guess that terminal would be the end. So here what I have is I have 3 carbonyls. Okay? And instead of thinking of H's and R's, we could think about internal and terminal. So right away, how many of these carbonyls are terminal? Meaning that they are on the very last carbon of whatever chain they're on. And the answer is 2 of them are terminal. This one is terminal because it's at the end of that long chain, and this one is actually also terminal because it's at the end of that branch. Does that make sense? Both of these also have an H that's not drawn. Okay? If they both have an H that's not drawn, what types of carbonyls are these? Aldehydes. Isn't that cool? So I really don't care which definition you use. I'm just trying to give you guys multiple ways of thinking about it. Alright? But I, a lot of times, used to get confused which one was which, and then I started just thinking aldehydes are on the end. I would always say that aldehydes are on the end, and that would help me. Alright? So lastly, what about this carbonyl here? This one's not terminal because it has more, it has an R group right there, so it has more carbon coming off of one of the sides. So basically, this carbon would be internal because it's surrounded by carbon on both sides, so this would be my only ketone on this molecule. Alright. So I've got my ketone. I've got my aldehydes. Learn to recognize them. I'll give you guys practice with this. Now notice that these are only ketones and aldehydes because they don't have other types of atoms next to them. If they had an oxygen or if they had nitrogen, then they would become the other functional groups that we talked about like amides and stuff like that.

How to write the condensed structures for aldehydes and ketones.

So now I want to talk about the condensed structures. The abbreviations for these can be a little confusing. For ketone, it's actually just going to be and this can get confusing sometimes. It's gonna be COC. And what that means is that sometimes your professor is going to be nice enough and give you C double bond OC. That means that it helps you understand that this is a carbonyl. But sometimes, they're just going to say COC and they're going to expect you to know that there's a double bond O in between. Now, some of you guys might be wondering, well, how is that different from an ether then? Because an ether is ROR, remember? So how is COC different from ROR? Because if it were an ether, it would be CH₂OCH₂ and then the rest of the R group. R here and R here. Notice that both of those carbons would have 2 H's coming off of them. Whereas, for the carbon right here, that carbon is never going to have H's coming off of it. That means that the R group is going to be directly attached to a carbon that does not have any hydrogens on it. So basically, the carbon that I'm looking at is right here. I tried to use a different color. That carbon right there is never gonna have hydrogen, so that's the difference. Instead of saying CH₂O, it's just gonna say CO. And when you see the CO, that tells you that this is a ketone and not an ether. This would be an ether down here, by the way. I'm not trying to confuse you. It would be ROR, it would be an ether. Okay? So like I said, I'm kind of going above and beyond here. Hopefully, your professor gives it to you like this. If they give it to you like that, then we're fine because you have the double bond there, it's very easy. But if they give it to you like this, then you need to look at the fact that it's CO, meaning C double bond O.

Finally, aldehyde kind of sucks too. The abbreviation for aldehyde is probably one of the worst ones in organic chemistry, and it's CHO. How does that make sense? I do not even know. I think of it like a choo choo train. Like, it's CHO. There's really not a good way to remember it other than just to memorize it. I still have students in Orgo 2 that will forget that CHO is an aldehyde. So I would just say commit it to memory, make sure you don't get confused. Make sure that you just give extra special attention to aldehydes.

How to recognize nitriles.

So Nitrile, this is a functional group that I really never have problems teaching because it's so weird. Basically, it's so much different from the others. It's just going to be C≡N. It starts with N and it has an N in it, so it's a Nitrile. And, the abbreviation for this in condensed formula is just CN. Okay? So that makes it really easy. If you see CN, that just means C≡N.

The difference between phenyl and benzyl groups.

Then finally, we have benzene. I've been avoiding benzene for a while now. I haven't really talked a lot about it. But now I want to give it some attention. So, benzene is a type of aromatic compound. Okay? We will not learn about aromatic compounds until Organic Chemistry 2. So I'm not going to explain what that means. I'm just going to ask you to know that it exists. Okay? That's when we actually get to the fun in Organic Chemistry 2. Right? But, for right now just note, be able to recognize it.

And it actually has 2 different names when it's a branch on a larger chain. Okay? If it's just by itself, like the Clutch logo. Okay? If you just see it by itself, that's Benzene. Just say that that's Benzene or you can also call it aromatic.

But when it's part of a larger chain, it gets its own types of branch names. So, for example, when it's directly attached to an R group, the name isn't benzene anymore, it turns into Phenyl. Okay? And Phenyl indicates that I have a benzene directly coming off of a chain. The way that we write it in condensed formula, a lot of times it's as C₆H₅. Okay? Because it has one hydrogen missing because it's directly attached to a large R group. Okay? And then also it can be abbreviated as Ph. Okay? But this isn't the pH that you saw in acids and bases where you have like a lowercase p and a big H. This is like both of them are lowercase. Okay? Cool.

And then, if there happens to be an extra CH₂ group, just like in between the benzene and the ring, then it gets even a different name, and that name is Benzyl. Now this one, to me, is counterintuitive because if I were writing organic chemistry from the very beginning and I saw a benzene group on a chain, I would say, oh, that's a benzyl group because alkyl alkyl, like alkane alkyl. So I would say benzene benzyl.

That makes sense. But it turns out that, for some reason, they decided to name the one attached to it as Phenyl and the one that's one carbon away as Benzyl. So it's kind of flipped from what you would think. And that's why I want to point out that Benzyl always has that CH₂ in the middle. The way that we would abbreviate it is as CH₂C₆H₅. So notice that there's that CH₂ in there. And then it's also abbreviated as Bn. Okay? Not often, but I have seen that before.

So I've got this long chain with 2 benzenes on it and I want you guys to tell me which one is the phenyl, which one is the benzyl. So go ahead and look at it for a second and then let me know. So this one would be the phenyl because it's directly attached right here. And then this one would be the benzyl because it has one carbon in the middle. It has an extra CH₂. Does that make sense?

So that's a benzyl and a phenyl, and that's the way we're going to use them when we're naming benzenes on rings.

Identifying Functional Groups

So what I want to do is just a worked example just between you and me, free response. Go ahead and try to identify all the functional groups in this molecule. So first of all, tell me how many functional groups are there. Is it 3? Is it 5? Is it 7? Go ahead and tell me. Then go ahead and try to identify each one and if applicable, tell me what the degrees are. So tell me if it's an amine, tell me that it's secondary or whatever. So go ahead and try to do that. Pause the video and then let's go ahead and talk about how many functional groups and what they are. Alright. So that was a little tricky. I think that it was even more tricky because I gave you some condensed formula in there, so it kind of threw you off a little bit. Students typically hate to work with condensed formulas. So if you didn't mind it, then good. So first of all, how many functional groups did you guys find? And the answer was 3. Okay? Because I had this double bond, I had this oxygen over here and then finally I had that iodine. Okay? Now some of you guys might be wondering what about alkane? We learned that alkanes single bonds between carbons and carbons are functional groups. We talked about it. Actually, it turns out that alkane, I should have mentioned earlier, is the only one that we don't consider a functional group because alkanes are the backbones for all of organic chemistry. So and they happen to not be very functional. In fact, they barely do anything. So when we're talking about functional groups, we're talking about things that are different from alkane. So that would be these three things. So what was the name of this first one? This would be an alkene. Okay. What was the name of this one right there? This one actually gets tricky because I want you to name degrees too. So this would be an alkyl halide and particularly, it would be a secondary alkyl halide. Why is that? Because it's attached to 2 carbon groups. The iodine, it would be named as a hydrogen. So I would count 1 carbon, 2 carbons. Cool? And then finally, what did you guys get for this last one? This would be ether. K? Because this falls into the ROR category, where I have ${\text{R}-\text{O}-\text{R}}$ and there's no carbonyls around, so this would not be like an ester or anything like that. Cool? So does that make sense to you guys so far? Hopefully, this is helping you guys to reinforce all the groups that we just learned. So, let's go ahead and go to the next page.

Recognizing acyl chlorides and anhydrides.

So now we're going to work on some groups that not all books make you know, but your book does. So we're going to go ahead and go over them just to be safe. Alright? So, acyl chloride. Acyl chloride, you can think of it like an aldehyde, but instead of having an H, it has a Cl. Okay? And the acyl chloride has a condensed structure of basically RCOCl. Okay, so if you ever see that, that's an acyl chloride. We're not going to work with these a lot in Organic 1. Okay? We're actually not going to see these again until Organic 2. We're going to work with them a lot. Okay? But it's cool. It's good that you guys know these ahead of time.

Then you've got another one that has to do with carbonyls and that's anhydride. An anhydride is a little bit tricky. Think of it almost like an ether, ROR, but instead of having just R groups, it has carbonyls on both sides. Okay? So it turns out that the way to name an anhydride, through condensed structure is pretty tricky. The way that, I mean sometimes it's just listed out exactly the way it looks, so that would be, let's just write that out, CH3COCOCH3. Okay. So you can see that was a little bit tricky. Alright? But sometimes it's also written with the O in the middle leading off and that's the one that I happen to see a little bit more. So that would just be that you take the O and then you have everything on both sides, since they're the same in this case, in parenthesis. C, O and then R, whatever R group you have, but that would be this R group right here and this R group right here times 2. And that basically tells you that you have we're splitting this thing down the middle and we've got one of these things and we've got the second one there and both of them are COR. Alright. So there you go. Acyl chloride and anhydride. You're not going to have to work with these too much, but maybe just recognize them for the test.

Recognizing sulfur compounds

Then finally we've got sulfur compounds. Now why am I listing oxygen again? Because sulfur happens to be right below oxygen on the periodic table, so it's going to make very similar structures to oxygen. Okay? So what I want you to think of is what would this structure be like if it was oxygen? What would it be called? And then what is it called if it's sulfur? So let's start off with the oxygen ones because I know you guys can help me with these. What type of group do we make if it's terminal? Basically, if the O is at the end of a carbon chain, what is it called? Good job. That's called an alcohol. You got this. All right. How if it's internal, meaning that the O is sandwiched between 2 carbons? We just talked about this. Ether, R-O-R, scary stuff. Right? So there we go. We have our terminal is an alcohol. Internal is an ether. Okay? So now let's talk about the sulfur. Sulfur, like I said, right underneath O, so it still wants to have 2 bonds, so it's going to make very similar compounds. If the S is terminal, it's going to instead be called instead of alcohol, it's going to be called a thiol. Okay? So thiol instead of alcohol. Then instead of an ether, if it's on the inside, meaning it has carbons on both sides, it's going to be called a sulfide. Okay? So these are just names that you literally need to memorize. You don't necessarily need to know degrees for these. But if you were asked the degree of a thiol, it would be the same way as an alcohol. So this would be what we would actually call a primary thiol because it has only one carbon attached to that carbon.

PRACTICE:The following molecule contains several functional groups. Of the choices given, select the most appropriate answer (not all functional groups may be listed). 

• A. Amide, Carboxylic Acid, Ether, Alkene
• B. Ketone, Alcohol, Ester, Nitrile
• C. Ether, Alkyne, Aldehyde, Carboxylic Acid
• D. Nitrile, Alcohol, Alkene, Ether

PRACTICE:Identifying functional groups. Select the most appropriate answer. 

• A. Ketone, Alcohol, Ester, Nitrile
• B. Amine, Carboxylic Acid, Ether, Alkyl Halide
• C. Alkyl Halide, Ester, Ether, Aldehyde
• D. Ketone, Alcohol, Alkene, Amine

PRACTICE:Identifying functional groups. Select the most appropriate answer. 

• A. Alkyl Halide, Ester, Ether, Aldehyde
• B. Aldehyde, Ketone, Amine, Alcohol
• C. Alcohol, Alkyne, Amide, Carboxylic Acid
• D. Amide, Aldehyde, Carboxylic Acid, Alkyne

Here’s what students ask on this topic:

What are functional groups in organic chemistry?

Functional groups in organic chemistry are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. They are the key to understanding the reactivity and properties of organic compounds. Examples include hydroxyl groups (OH) in alcohols, carbonyl groups (C=O) in ketones and aldehydes, and amino groups (NH2) in amines. Recognizing these groups helps predict how molecules will react in different chemical environments.

How do you differentiate between alkanes, alkenes, and alkynes?

Alkanes, alkenes, and alkynes are types of hydrocarbons differentiated by the types of bonds between carbon atoms. Alkanes have only single bonds (C-C), alkenes have at least one double bond (C=C), and alkynes have at least one triple bond (C≡C). These differences in bonding affect their reactivity and physical properties. For example, alkenes and alkynes are more reactive than alkanes due to the presence of multiple bonds.

What is the difference between a ketone and an aldehyde?

Ketones and aldehydes both contain a carbonyl group (C=O), but they differ in their placement within the molecule. In ketones, the carbonyl group is bonded to two carbon atoms, making it an internal group. In aldehydes, the carbonyl group is bonded to at least one hydrogen atom, making it a terminal group. This structural difference influences their reactivity and the types of reactions they undergo.

How are primary, secondary, and tertiary alcohols classified?

Alcohols are classified as primary, secondary, or tertiary based on the number of carbon atoms bonded to the carbon atom that is attached to the hydroxyl group (OH). A primary alcohol has the hydroxyl-bearing carbon attached to one other carbon, a secondary alcohol has it attached to two other carbons, and a tertiary alcohol has it attached to three other carbons. This classification affects their reactivity and the types of reactions they can undergo.

What is a carboxylic acid and how is it formed?

A carboxylic acid is an organic compound containing a carboxyl group (COOH). It is formed when a carbonyl group (C=O) is bonded to a hydroxyl group (OH). Carboxylic acids are known for their acidic properties and are commonly found in various biological and chemical processes. They can be synthesized through the oxidation of primary alcohols or aldehydes.