What is the first step in the general mechanism for nucleophilic acyl substitution?

Question

Quizplus · Accepted Answer

The first step in nucleophilic acyl substitution is the addition of a nucleophile to the carbonyl carbon. This creates an unstable tetrahedral intermediate. The remaining steps involve loss of the leaving group and restoration of the carbonyl functionality. Protonation of the carbonyl (A) may occur later in the mechanism to facilitate loss of the leaving group, but it is not the first step. Removal of an α-proton (B) is a step in some related mechanisms, but not in nucleophilic acyl substitution.

What Is the First Step in the General Mechanism for Nucleophilic