Multifunctional Hydrolytic Catalyses. III. Catalytic Hydrolysis of p-Nitrophenyl Acetate by Imidazole-4-carbohydroxamic Acids

Imidazole-4-carbohydroxamic acids (I) and its N-methylhydroxamic acid derivative (II) were synthesized from imidazolecarboxylic acid and hydroxylamines, and the catalytic hydrolysis of p-nitrophenyl acetate was studied. The reaction was analyzed by the pseudo-first-order kinetics and the burst kinetics. The hydrolysis proceeds via the formation and the subsequent decomposition of the acetyl hydroxamate intermediate. The acylation rate with these catalysts were comparable to those observed with other simple hydroxamic acids. On the other hand, the deacylation of the acetyl intermediate of II was greater than expected and increased with pH. This suggests that the intramolecular imidazole group (neutral and/or anionic species) assists deacylation, thus increasing the overall efficiency of catalysis.