Question

Why are acid chlorides so reactive?

Answer 1

Because they contain an unsaturated carbonyl centre that is attached to a leaving group, the chloride ion.

Explanation:

The ipso carbon in `RC(=O)Cl` is electron deficient and unsaturated. The reaction with a nucleophile is facile. If the nucleophile contains an active hydrogen, i.e. If the nucleophile were `HOR`, the `HCl` generated could be removed by the addition of 1 equiv of non-nucleophilic base:

`RC(=O)Cl + HOR' + NEt_3 rarr RC(=O)OR' + Et_3N•HCl`