3
$\begingroup$

Can carboxylic acids like formic acid act as nucleophile in $\mathrm{S_N2}$ or $\mathrm{S_N1}$ reactions?

For example can formic acid react with an alkyl/aryl halide like benzyl bromide?

I'm asking because I found a very similar question while going through some old organic chemistry test papers. However none of the book's I have read says that carboxylic acids can act as nucleophile in such cases.

$\endgroup$
2
$\begingroup$

Carboxylic acids can act as nucleophiles of course. Consider reactions with isobutene or thionyl chloride (although base certainly helps in this latter case). However, whether it's in $\mathrm{S_N2}$ or $\mathrm{S_N1}$ reaction mechanisms is another matter. If you beast something with enough heat it will usually react. I would not be surprised if a carboxylic acid reacted with triflouromethanesulfonic anhydride without base. It's still $\mathrm{S_N2}$ as mechanistic studies have shown the S=O bonds do not open up like acyl electrophiles. I suspect you would need to resort to a continuous as opposed to a batch approach to push a reaction between the acid and an alkyl halide without using any base. Expose the reaction to high temperature (I'm thinking 250C and higher) for 5 seconds or less under continuous liquid flow.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy