[bri3432]

Hi, I am Working on a practice problem right now and can't figure out a key mechanistic step which converts the Ester into an Acyl chloride. The only thing we have been taught is to convert carboxylic acids into Acyl Chlorides using SOCl2. Could anybody provide some help as to how the Ammonium Chloride would convert the Ester into an Acyl chloride? Thank you! The problem is attached

[Babcock_Hall]

It is a forum rule that you must show your attempt or give your thoughts before we can help you.  Nevertheless, I will provide a suggestion.  Why is the reaction very, very slow in the absence of ammonium chloride?  What sort of chemistry can the ammonium ion perform?

[bri3432]

Esters are not very reactive. That is why I suggested that somehow it needed to be converted to an Acyl chloride. The NH4+ counter ion could act as an Acid catalyst for the reaction, and the Cl- could possibly attack the Ester to form an Acid halide. This is what I think occurs, but from everything I have learned, the Chloride anion is not nucleophilic enough to attack an Ester due to its low reactivity.

[wildfyr]

I disagree that this passes through an acid chloride

[bri3432]

The only other possibility that I have come up with is the NH4Cl's catalytic role being to convert the Ester to a Carboxylic acid, which then reacts with the Amine to form the product.

[bri3432]

actually that isn't possible because there is no water present in the reaction.... I'm at a dead end.

[bri3432]

I drew out a mechanism. Can Someone let me know if it is correct? I have to turn in this problem in the next 30 minutes...

[bri3432]

How does this look

[Babcock_Hall]

I think what you now have is on the right track, but the details may not be all in place.  What do you think the identity of "B" is?  One might also ask whether or not the leaving group could be protonated before or during its departure.

[aya ghonim]

Hello, I think NH4 will act as a base catalyst, what I cant understand is that the whole NH4Cl is actually slightly acidic. This brings me back to point zero. any suggestions about the exact mechanism ?