Synthesis of polymer catalysts containing vinyl-imidazolehydroxamic acid and their ester hydrolysis catalytic activity

The hydrolysis of p-nitrophenyl acetate catalyzed by polymers containing imidazole-4-carbohydroxamic acid has been studied. Radical homo-and copolymerization of the protected vinyl monomer, _N-methyl-(1-vinyl-imidazole-4)-carbohydroxamic acid benzyl ester (3a), and the subsequent removal of the benzyl group, produced water-soluble polymers containing the imidazole-4-carbohydroxamic acid group. The hydrolysis of p-nitro-phenylacetate catalyzed by the imidazole-4-carbohydroxamic acid derivatives was analyzed by burst kinetics and proceeded faster than did that catalyzed by imidazoles or carbohydroxamic acid. The catalytic activity of the polymer was less than that of the monomeric analogue. The observed rate constant of acylation was proportional to the dissociation degree of the carbohydroxamic acid group and was especially low in the negatively charged polymer 13a. On the other hand, the acylation was favourable to the positively charged polymer catalyst 13c due to its lower pK_a value, but the de-acylation process was retarded.