00:01
All right, in this problem, we're looking at this molecule for aspartame, and the first part of the question is asking about chiral centers and stereoisomers.
00:10
So, let's identify our chiral centers.
00:14
Remember that a chiral center is a sp3 carbon with four different groups attached to it.
00:20
So to identify these, we're going to look at all of our sp3 carbons.
00:24
So this one is sp2, so we ignore that one.
00:27
This one is sp3, but remember that this has two hydrogen.
00:31
Attached to it.
00:33
So two of the same groups.
00:34
So this is not chiral.
00:36
We go to this one.
00:38
There's one on this one.
00:41
So we have hydrogen, an amid group, an mean, and then another carbon.
00:48
So this one is a chiro center.
00:50
We're going to indicate that with a little dot.
00:53
This next one is sp2.
00:55
And then this one is also sp3.
00:58
So we'll look at this guy.
01:00
This has one hydrogen on it.
01:01
So if it has a hydrogen, a carbon with an oxygen, a carbon not with an oxygen, and a nitrogen.
01:09
So this guy is chiral.
01:13
This one is sp2, so we ignore that one.
01:17
This guy down here, two hydrogens, two the same, not chiral.
01:23
So we have total of two chiral centers.
01:29
And to figure out how many stereo isomers we have from that, we can do our little formula, 2 to the number of stereosomers.
01:37
So 2 to the 2, which equals 4.
01:40
So we have 4 stereoisomers.
01:47
Now we're looking at functional groups.
01:50
So let's highlight those.
01:54
So over here on the end, we've got a carboxylate ion.
01:59
Right here, we have an amine.
02:01
Whoops.
02:03
Right here we've got an amid.
02:05
And then over here is an ester.
02:10
So remember an amid is a carbonyl with an n next to it, an ester is a carbonyl with an o.
02:16
So we have a carboxylate, an amine, an amid, and an ester for our functional groups.
02:34
Now the next part asks us to identify the net charge of the molecule at ph 7.
02:40
So let's take a look.
02:42
At the spots of this molecule that we have to pay attention to.
02:48
So here is a carboxylate and here is an amine.
02:52
These are the only two places on this molecule that would, sorry, and there's another, and right here.
02:57
These are the places on this molecule that would be charged or uncharged, depending on ph.
03:03
So a carboxylic acid has a pca of about five.
03:14
And since we're at ph 7, the ph is higher than the pca.
03:20
So this would keep its negative charge as shown here...