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.
So 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.
In this case, this first amine that we're looking at would be a primary amine because
it is attached to only one 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 means, 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 a quaternary amine by definition is always going to have a positive charge.
Why?
Because that nitrogen does not like to have four 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.
They way to name primary amines is pretty straight forward.
What we're going to do is we're going to add the suffix -amine to the name of the alkyl
substituent.
So we look at the alkyl group, and like we did for other functional groups, we'd say
this is a modifier.
So we'd change the 'e' in the alkene for amine at the end.
Other than that it's like naming a regular alkane.
So we can look at this first version here, this first molecule, and we could say 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 three 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.
So I'm just going to make this one 1, this one 2, and this one 3.
What that means is that we have two things going on on that 2.
We have a methyl group.
That's a methyl.
And we have the amine.
Right?
Awesome.
So 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-methyl and then 2-propanamine.
So 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 off the 'e.'
I'm adding amine because it's on the second carbon so that's why it's a 2-propanamine.
All right.
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.
So how is that going to change the name?
Well, we're going to have to name it as a cycloalkane substituent.
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 would have the higher priority.
Would the 1 go on the methyl or would the 1 go on the amine.
That's because you could either name it as the amino group, whatever, the amine on the
1 and the methyl on 2 or you could 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've 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 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?
Again, I think I'm going to run out of 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-cyclobutamine.
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 two.
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 1 there?
Because I'm giving priority to the amino group.
Awesome guys.
So 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?
All right, so 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.
So I'll just go ahead and write it down.
The name for this one is going to be aniline.
So aniline is also a primary amine, guys.
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 molecules are some of the oldest ones in organic chemistry, so
we always tend to go with those common names.
All right?
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.