00:01
Okay, this problem is asking us to show the mechanism of a hydrolysis reaction followed by a nucleophilic asyl substitution reaction.
00:06
Okay, so my starting material is this.
00:09
I have two methyl groups and then my two oxygens, and that is going to form a collective acetatelle.
00:15
And then attached to here, i have a methyl group, and attached to there i have a carboxylic acid.
00:21
Okay, so as stated in the problem, this is going to undergo a hydrolysis reaction.
00:26
So using h3 or hydronium ion, i'm going to pre -edin the problem.
00:30
Protonate one of these oxygens.
00:33
And i'm actually going to protonate this oxygen.
00:35
And the reason because of that, the reason i'm doing that is because right now i have an acetal.
00:40
An acetyl is basically something that looks like this.
00:43
Okay.
00:43
An acetyl can actually convert into a ketone using hydrolysis.
00:48
And this is a totally reversible reaction so i can convert my ketone into an acetyl and i can convert my acetyl into a ketone.
00:55
Okay.
00:55
So i'm going to accomplish just that.
00:57
And this is as, this is the, how the mechanism goes.
00:59
So i'm going to protonate my oxygen as part of the acetal first and after that i will end up with this product in which i have same thing except now i have a protonated oxygen and of course i have my methyl group and my carboxylic acid there okay so now that that is protonated that means that that oxygen has a positive charge because in organic chemistry we usually don't like to see things with positive or negative charges we're going to want to relieve that immediately so i'm going to move the electrons from this bond onto the that oxygen to relieve of its positive charge, and in the process of doing that, this carbon has, well, will have a positive charge after that, this electron movement.
01:42
So if this carbon has a positive charge, i want to try to avoid that too.
01:45
So i'm going to move the electrons from this oxygen down to make a double bond there.
01:48
Okay, so we can actually have that positive charge there on the carbon, but this is just a resonance form just so we can see the next step more clearly, okay, because this auction is going to have a positive charge too.
01:58
Okay, so after that, i'm going to have this product in which i have the leaving group leave, my alcohol leave, and i have this.
02:06
Okay, so now i have to work with this.
02:09
And if we remember back to my starting material, i had hydronium ion, and then i deprotonated it to make water.
02:16
So that means that i have water currently.
02:19
My water is going to behave as a nucleophile to attack my carbonyl.
02:24
Okay, when i attack my carbonyl, the electrons are going to move up to my oxygen to relieve the oxygen of its positive charge, resulting in.
02:30
This compound.
02:32
So almost the same thing, but now i just have an extended chain.
02:39
Okay, so methyl group, and then my carboxylic acid, and then i have the newly added water.
02:47
So i'm going to write down an alcohol that is protonated.
02:51
Okay, so because that, that i have that water there, and because it is protonated, it has a positive charge.
02:57
I don't want that there.
02:58
I don't want to have a positive charge in general, but i'm going to want to make this group leave eventually.
03:02
And in the state that it is right now, it is not a particularly good leaving group, so i want to make it into a better leaving group.
03:07
And the best way to do that is to protonate it.
03:10
And luckily right here, i do have an extra proton, proton, so i'm going to use a proton transfer.
03:15
And this is where difference in teaching might happen, because some teachers might teach it in which an intra -molecular reaction happens, in which this oxygen directly takes that proton.
03:24
Others will teach an intermolecular reaction, but nearly all will just teach a proton transfer in general.
03:32
Okay, so after that, i get the following compound, which i have a matter.
03:36
Methyl group there, carboxylac acid, etc.
03:40
Okay, so now that this has a proton, this group has a positive charge.
03:45
That means it is vulnerable to leaving.
03:46
So i'm going to make it leave.
03:48
Okay, and then as i do that, this carbon has a positive charge, so i want to avoid that.
03:53
In fact, i'm going to bring the electrons down from this oxygen to relieve that carbon of its positive charge, but i'm also going to make a positive charge on that oxygen in the process.
04:01
So i'm going to have this protonated ketone, and then i'm going to have the result of my leaven group.
04:08
So my two alcohols, diol, and then the result, the carboxyl acid.
04:15
Okay, so because i have this protonated ketone, that means it has a positive charge.
04:19
I'm just going to utilize a base, such as water, so i still do have water in the solution.
04:26
My water is going to come in and deprotonate that protonated ketone, resulting in the following.
04:32
I just have this as my final product for this part of the reaction.
04:36
Okay, so i just end up with a ketone.
04:37
That is, because of the hydrolysis of my acetyl.
04:40
And then i still have this compound to work with, this one right here.
04:44
Because this is going to undergo a nucleophilic acal substitution.
04:48
Okay, so working with this now, in fact, i'll just move this down so i know i'm working with it.
04:56
Okay, so moving this down and erasing this circle, i'm still in acidic conditions.
05:01
The reason i'm in acidic conditions is because after the deprotonation of this ketone, i ended up with hydronium because i protonated water...