Mechanism for acetic acid-catalyzed ester aminolysis

A computational study is described to elucidate the mechanism for acetic acid-catalyzed ester aminolysis to produce amides. A concerted acyl substitution mechanism is proposed to involve concurrent acylO bond cleavage and acylN bond formation where acetic acid acts as a bifunctional catalyst connecting to both the alkoxide and the amino moieties. This mechanism does not involve the intermediacy of a tetraheral adduct nor the rehybridization of acyl carbon, in sharp contrast to classic stepwise acyl substitution mechanism.