[oxygeniscoool]

How to know which intermediate that is formed in the first step (H -> J)? Which first steps are first in this mechanism?

[Mitch]

The thionyl chloride converts the carboxylic acid to an acid chloride. Can you attempt to draw the mechanism knowing that?

[oxygeniscoool]

So, the sulfur atom is attacked?

[oxygeniscoool]

The thionyl chloride converts the carboxylic acid to an acid chloride. Can you attempt to draw the mechanism knowing that?

I don't really understand the process after all. Is NH₂ attacked?

[Mitch]

No, the amine is not attacked first. I think you need to review SOCl₂ chemistry: https://www.masterorganicchemistry.com/2011/12/03/reagent-friday-thionyl-chloride-socl2/

[oxygeniscoool]

No, the amine is not attacked first. I think you need to review SOCl₂ chemistry: https://www.masterorganicchemistry.com/2011/12/03/reagent-friday-thionyl-chloride-socl2/

Okay, thanks!

[wildfyr]

I gotta say, it is a little weird to expect a acyl chloride and aniline to exist together. I guess the amine is protonated quite quickly but even so... I would have expected some amount of oligomer if you don't move fast.

[OrganicDan96]

wouldn't the aniline be protonated all along by the carboxylic acid?

[wildfyr]

Just a plain amine, yes. But the Wikipedia page of anthranilic acid suggests they are present in both forms in the absence of another acid or base.

Aniline is too weak a base to fully deprotonate a carboxylic acid at 1eq.

Edit: here's the paper wiki is referring to https://royalsocietypublishing.org/doi/10.1098/rspa.1968.0003

DOI:10.1098/rspa.1968.0003

[kriggy]

I think the aniline is not really THAT reactive (I had some problems making amides without additional base). I mean there is highly deactivating group on the ring (not in conjugation though) and methyl grop ortho to amine proceting some steric hinderance. Also, methanol is in high excess.

Also, its possible that the reaction procees via formation of methylchloride from methanol and then alkylation of the carboxylic acid?

[clarkstill]

I agree anilines aren't all that nucleophilic (certainly nowhere near as nucleophilic as alkyl amines). However, they are almost certainly more nucleophilic than carboxylic acids, which raises the question why does the SOCl2 react with the carboxylic acid not the aniline? Or does it react reversibly with the aniline? Maybe it's just early in the morning and I'm being dumb.

[wildfyr]

Usually a huge excess of thionyl chloride is used in chlorination reactions. I typically use it as the solvent along with a catalytic drop of DMF.

So yeah, probably some gets consumed making the ammonium chloride salt, but there's plenty left to make acid chloride.

Kirggy, under acidic conditions that methyl chloride reaction doesn't sound very good. It's a very ordinary way to make esters to make the acid chloride, not really isolate it, then dump in a bunch of your desired alcohol.