A-Level Carboxylic acids, acyl chlorides and esters: worked solution

Question

Acetylcholine, [CH3COOCH2CH2N(CH3)3]+, is easy to prepare from cheaply available starting materials, yet it is not given directly to patients because it breaks down readily in water, even when no acid or base catalyst is present. Propose a reason why acetylcholine is hydrolysed more easily than a typical ester.

Acetylcholine carries a positively charged quaternary ammonium group, -N(CH3)3+, close to the ester carbonyl. This electron-withdrawing positive charge makes the carbonyl carbon more electron-deficient (more electrophilic) than in a typical ester, so it is more readily attacked by a water nucleophile, speeding up hydrolysis.