Multifunctional hydrolytic catalysis. II. Hydrolysis of p-nitrophenyl acetate by a polymer catalyst which contains hydroxamate and imidazole functions

A water-soluble polymer catalyst was prepared by radical polymerization of a protected hydroxamate monomer, 1-methyl-2-vinylimidazole and acrylamide, and by the subsequent NH₂NH₂ treatment of the polymer. The hydrolysis of p-nitrophenyl acetate by the bifunctional copolymer obeyed typical burst kinetics: rapid accumulation of acetyl hydroxamate group and its slow decomposition. The acetylation rate of the hydroxamate group was rather close to that of a polymer which does not contain the imidazole unit. However, the deacylation was markedly accelerated by the presence of the imidazole unit, and the difference in rate constants amounted to 60- to 80-fold at pH 8-9. These results indicate that the overall catalytic efficiency of the bifunctional polymer is enhanced due to the complementary action of the imidazole and hydroxamate functions.