33.3.3—Mechanism: acyl chlorides in reactions

A nucleophile adds to the electrophilic carbonyl carbon of an acyl chloride, forming a tetrahedral intermediate. The intermediate then eliminates chloride and reforms the C=O bond.

This mechanism explains why several nucleophiles give different products while the acyl carbon remains the reaction centre.

In ethanolysis, ethanol attacks CH₃COCl, the tetrahedral intermediate collapses, and ethyl ethanoate forms with HCl as the by-product.

The mechanism is not direct displacement without an intermediate, and the carbonyl bond is temporarily changed rather than permanently lost.