00:02
Okay, we're asked to show a mechanism for the acid -catalyzed reaction of salicylic acid with acetic -anhydrate.
00:10
So let's begin with the structures of salicylic acid, then acetic anhydride.
00:36
Now, to begin with, we could simplify things greatly when we recognize that the reactivity of acetic anhydrides is with alcohols, especially in acid acidic solutions.
00:49
And that the bulk of this structure here, the only thing.
00:53
That matters is that we've got r -o -h.
00:57
So we can essentially ignore everything going on there.
01:00
We don't have to draw it each time.
01:02
But when we're done, we'll redraw the entire structure back in.
01:06
But for now, this is to stand in for the rest of our salicylic acid.
01:10
R -o -h is all that matters.
01:14
So what is the first step in the acid -catalyzed reaction of salicylic acid of acetic anhydride? it's going to be protonation of one of these carbonyls on acetic anhydride.
01:25
That's a very common first step in the acid -catalyzed reaction of any carbonyl species.
01:33
So this will pick up a proton yielding what is essentially a supercharged form of acetic anhydride.
01:46
That's because it is in residence with this form.
02:07
So the proton has effectively made this carbon more electrophilic than it would be otherwise.
02:17
That's basically the point of the acid catalysis is to make this carbon right here more reactive than it otherwise would be...