Naming Amines - Online Tutor, Practice Problems & Exam Prep

Amines are classified into primary, secondary, tertiary, and quaternary based on the number of alkyl groups attached to nitrogen. Primary amines are named by adding the suffix "amine" to the alkyl group, while secondary and tertiary amines require notation for substituents directly off nitrogen, denoted as N-substituents. When higher priority functional groups like carbonyls are present, "amine" is replaced with "amino." Understanding these naming conventions is crucial for accurately identifying and communicating about amines in organic chemistry.

Naming Primary Amines

Hey guys. In these next few videos, we're going to focus on how to name amines. So you might recall from prior videos that amines can exist as several different degree states. You can have primary, secondary, tertiary, and even quaternary amines. And unlike other functional groups where you pretty much always have the same naming system for all of the molecules in that functional group, amines are different because the type of name that you assign is going to depend on the degree of the amine.

Before we can even talk about IUPAC names, let's refresh on what the different degree systems for amines are. Remember that the degree of the amine is going to be dependent on directly how many R groups are attached to the nitrogen. So in this case, this first amine that we're looking at would be a primary amine because it is attached to only 1 R group. As you look at the second example, the second example is now a secondary amine because I've got an R here. I've got an R here. That is a secondary amine. So then we go up to tertiary. Tertiary amines, as you guys remember, they don't have any hydrogens because it's just all R groups. And then finally, we have quaternary amines. Now quaternary amine by definition is always going to have a positive charge. Why? Because that nitrogen does not like to have 4 bonds. This is going to have a formal charge and we're not going to focus on these for this lesson since it's in an ionized state. We're only going to focus on the neutral versions of nitrogen.

Let's go ahead and talk about the simplest type of amine which is a primary amine. The way to name primary amines is pretty straightforward. What we're going to do is we're going to add the suffix amine to the name of the alkyl substituent. We'd look at the alkyl group and like we did for other functional groups, we say this is a modifier. So we change the E in the alkane for amine at the end. Other than that, it's like naming a regular alkane.

So we could look at this first version here, this first molecule and we could say, okay, how do we name that R group just as the R group itself and then we just have to add amine towards the end. Let's just go ahead and do this one together. What we're going to notice is that the longest chain is 3 carbons. What we notice is that there's really no preference for 1, 2, and 3 here in terms of the locations because it's symmetrical. I'm just going to make this one 1, this one 2, and this one 3. What that means is that we have 2 things going on on that 2. We have a methyl group. That's a methyl. And we have the amine. If we put that all together, what is that name going to be? Well, we would just name it as an R group then with the amine at the end. So what you would say is that this is going to be a 2-methyl-2-propanamine.

This name got a little bit longer than the line underneath it but I hope you guys were able to fit that in. Basically, what we're doing is we're just naming the longest carbon chain. We're naming the methyl as a substituent and then I'm adding the amine part at the end. I'm taking out the E. I'm adding amine because it's on the second carbon, so that's why it's a 2-propanamine. Alright, got it? So let's go ahead and do the next one. Let's look at the next one. So this next one, the R group is in this case a ring. How is that going to change the name?

Well, we're going to have to name it as a cycloalkane substituent 1. In this case, if I were just to kind of ignore the nitrogen, what would I be looking at? I'd be looking at a methyl group again. But in this case, my R group is cyclobutane. Now in terms of priority, we do have to ask ourselves a question here. If you were looking at the ring, which one have the higher priority? Would the one go on the methyl amine? That's because you could either name it as the amino group or whatever the amine on the 1 and the methyl on 2 or you can name the methyl on the 1 and the amine on the 2. What's your suspicion? Which one do you think is going to get the higher priority? You got it. Amine is a modifier and as a general rule, anything that modifies the root name is going to have higher priority than a methyl group. That means that I'm going to choose to have my amine as my 1 and my methyl as my 2.

Putting that all together, what would we get? Well again, I think I'm going to run out of a little space here. I'll try to write it a little smaller. But what I'm going to get is something that looks like this. 2-Methyl-1-cyclobutanamine. Why is that? Let's just break that down a little bit. The reason for that name is that we've got the methyl group on the 2. We've got a cyclobutane. Oh, I'm sorry. It should have been butanamine. That is my bad because we're only supposed to exchange the last E. So what I should have actually written was let's get our erasers out, butanamine. 1-Cyclobutanamine because I'm taking out the last E and I'm replacing it with amine. And why is there a one there? Because I'm giving priority to the amino group.

Awesome. Then we've got one last example. You guys might remember this molecule from our aromatics chapter. What do you guys think the name of this one is? This one doesn't get an IUPAC name because it is one of the common names for benzene that you guys are supposed to be familiar with already. I'll just go ahead and write it down. The name for this one is going to be aniline. Aniline is also a primary amine but it's one that we're going to prefer to use the common name for because it's benzene. And we know that benzene molecule is some of the oldest ones in organic chemistry, so we always tend to go with those common names.

So guys, I hope that made sense how to name primary amines. Now let's go ahead and flip the page and talk about secondary and tertiary amines.

Primary Amines as Substituents

Alright guys, one more thing before we move on to secondary and tertiary. What happens if you have a primary amine? We've got a primary amine here, but it is not the highest priority group. What if a higher priority functional group is present? Because we just talked about how amines are higher than alkyl groups. But you guys might recall that carbonyls are some of the highest priority groups in nomenclature. What happens if I have a primary amine, but I have a carboxylic acid or some other kind of carbonyl, aldehyde, ketone, etc? Well then, how would we name this? When that happens, you're going to change the suffix amine. You're not going to use that anymore, and you're going to replace it with the prefix amino. You're going to name it as a substituent because the root is now going to be given to the higher priority group. So that means that now this is your root, this is your modifier. Remember that we keep referring to a modifier as anything that changes the parent chain name. The amine is now going to be the substituent. How do you name an amine as a substituent? Well, you don't name it amine anymore. Now you call it amino. If you ever heard of an amino acid, an amino acid is going to be a carboxylic acid with an amine as a substituent. That's why it's called amino. That's beyond the scope of this lesson, but just letting you know that you've heard of this term before. So in this case, what's going to be the root name for this molecule? The root name or the common name would actually be benzoic acid. This is going to be benzoic acid. You guys might recall from our aromatics chapter.

Benzoic acid. That means that my NH₂ is going to be named as an Amino. And it's going to be on which position? What number? 3. This would be on the 3 position. What you could call this is you could say that this is 3-amino benzoic acid. You guys might recall that we actually have other types of nomenclature to denote these 1, 2; 1, 3; and 1, 4 relationships. This would also be probably more commonly referred to as meta-aminobenzoic acid. Remember that when you say when you use the words meta, ortho, and para, they're just stand-ins for 1,2; 1,3; 1,4.

Awesome guys. So I hope that made sense. So now let's go ahead and talk about secondaries and tertiaries.

Naming Secondary and Tertiary Amines

So for secondary and tertiary amines, the naming gets a little bit different, and that's because we have to account for two different types of substituents. Remember that you can always have just an extra alkyl substituent coming off of your parent chain. Sure. But now, since it's a secondary or a tertiary amine, that means that we're opening up to the possibility of other R groups coming directly off of the nitrogen. How do we distinguish between an R group coming off of the parent chain and an R group coming off of the nitrogen? That's where the notation of N substituents comes into play. N substituents are the ones that are directly coming off of nitrogen, so it's going to be a big part of this name. Now the way we do this is we just take the longest alkyl group, the largest alkyl group and we make that our parent. Anything that's not on that parent chain, anything that's coming directly off of the N is going to be an N substituent. We can go ahead and do this first one as a worked example since I know it's a little bit weird to look at, and then I'll give you guys the second one as practice. First of all, what's the longest carbon chain? The longest carbon chain is 3, so I would choose it to make this my parent. As my parent, that means that this is going to be instead of propane, how does the name change? It's obviously not just propane. It's going to be propanamine. One more thing we're missing, the location. The nitrogen is coming off of which atom on that 3 carbon chain? 1. This is going to be a one-propanamine. Cool. Now we have to talk about all the other stuff. Well, I've got 2 other R groups and they're both directly coming off of my nitrogen. That means these are going to be denoted as an N substituent, meaning that this is an N-methyl and this is also an N-methyl. So I've got all my components, guys. I've got everything I need. I just have to put it together. Now instead of naming this as N-Methyl N-Methyl 1-propanamine, we can combine that. That's what we usually do. If you have the same substituent twice, you could just write it like this. So N,N-Dimethyl 1-propanamine. There you have it. That's the whole name. Great job on that first one. You guys followed along just great. Now let's see if you guys can put that together and get the totally correct name for the second one. It's all up to you. Go.

Name the following amines

All right guys. The first thing we had to analyze here was which one is the largest alkyl group, and that undoubtedly was my cyclopentane. Cyclopentane becomes what name does an amine? That would be now cyclopentanamine. Now there's a little bit of a debate here. Do we name it as one cyclopentanamine, like we did with the parent chain over on the other one, or do we just name it as cyclopentanamine? Well, it turns out, guys, that you might remember that if you only have one thing attached to a ring, you don't need to name the location. The reason is because every single location on that ring is exactly the same. So it doesn't matter. Putting the one there is just kind of pointless. Now what if you do add the 1? If you make it one cyclopentamine, you're not going to get any marks off your grade. But just letting you know that in real life, you're not going to see the one there because it's just extra ink. That being said, I'm just going to keep it as cyclopentanamine. What are the substituents? Like my other example, I've got an N-methyl here. But now this one's a little different because this substituent is different. This is an N-ethyl. So I've got an N-methyl, N-ethyl. How do I put all this together? Well, guys, when in doubt, alphabetical order. This final name is going to be N-ethyl-N-methylcyclopentanamine. Almost off the page here. As you can see, I put it in alphabetical order. You might be saying, Johnny, why did you not make it N,N like in the last example? Because guys, you only use N,N notation when you're using a di, when you have 2 of the same substituent. In this case, we have to put it in alphabetical order, so we'd have N,E and then N,M or whatever because we have the alphabetical order of E coming before M. If in your answer, you had an N-methyl-one cyclopentanamine, again, unnecessary but not wrong. Your professor wouldn't take off any points for that. That is how you name pretty much every amine that you'll need to name in this course. Let's move on to the next topic.