00:01
Okay, this problem is essentially asking us to explain why we break the acyl carbon oxygen bond as opposed to the alkyal carbon oxygen bond in the hydroxide -promoted hydrolysis of this ester.
00:10
Okay, so the whole purpose of isotopically labeling in oxygen is simply to keep track of where the oxygen goes as far as my products go to make sense of the mechanism that occurs.
00:20
Okay, so why am i breaking this carbon oxygen bond on the acetyl side as opposed to my alkyal carbon oxygen bond? okay, so let's go through the mechanism.
00:28
So if i had hydroxide promoted hydrolysis, i would have a situation in which my hydroxide performs as a nucleophile.
00:36
It's going to go ahead and perform as a nucleophile and attack this carbon of my carbonyl.
00:40
Okay, that is the most electrophilic site.
00:42
After i do that, i'm going to have to move the electrons up to that oxygen.
00:45
Okay, so as far as my product goes, i'm going to get my ph 3, my carbon with its oxygen connection.
00:53
So that oxygen has a negative charge.
00:54
That oxygen that i just drew out is this oxygen right there.
00:58
Okay, also attached to that carbon, we have the connection to my incoming hydroxide as the former nucleophile.
01:03
So this one right here corresponds to this one.
01:05
Okay, and then last but not least, we have the connection to my isotopically labeled oxygen.
01:10
So oxygen connected to ch2, ch3.
01:14
Okay, and of course that oxygen is number 18.
01:18
Okay, so now what? now we have to demonstrate why will we break this bond? okay, so after i form my carboxylac acid, so side note on this, anytime we have hydrolysis of a carboxylac acid derivative, for right now we have an ester, we could also have an acyl chloride, an hydride, etc.
01:36
But basically, anytime i have the hydrolysis of a carboxylic acid derivative, i'm going to transform it into either a carboxylic acid or a carboxylate ion.
01:46
In this case, because i am in basic medium, i'm going to transform it into a carboxylate ion.
01:51
So with that in mind, what group do i need to get rid of? i can either get rid of this group to transform.
01:57
Into my eventual ester, or i can get rid of this group to transform it into my eventual carboxlate.
02:05
Okay, so i need to get rid of this group in order to turn it into a carboxlate because, again, in hydrolysis, i turn my carboxylac acid derivatives into carboxylacet or carboxylac acids, never esters.
02:17
Okay, so after i get rid of this group, the whole purpose i got rid of that group was because i was able to move the electrons down from this oxygen to make my carbonyl.
02:26
Okay, so these are two simultaneous occurring steps.
02:29
I move down the electrons from my oxygen.
02:31
As i do that, i'm going to have to make my leaving group leave.
02:34
Okay, so as far as my product goes, i'm going to get my ch3, ch2, carbonyl with my oh.
02:41
So this is my carboxylac acid, and then i have the o connected to my ch2, and of course this oxygen is considered to be isotopically labeled.
02:51
Okay, so that's going to be my 18.
02:52
Okay, and we're going to have a negative charge on the oxygen...