MULTIFUNCTIONAL HYDROLYTIC CATALYSES - 9. HYDROLYSIS OF p-NITROPHENYL ACETATE BY BIFUNCTIONAL POLYMER CATALYSTS CONTAINING ZWITTERIONIC (HYDROXAMATE) NUCLEOPHILES.

In the reported experiments, the hydrolysis of p-nitrophenyl acetate by bifunctional polymer catalysts was studied in 28. 9% EtOH-H//2O at 30 degree C. Partial (ca. 10 mole%) quaternization of poly(4-vinylpyridine) and poly(1-vinyl-2-ethylimidazole) with benzyl N-benzyl chloroacetohydroxamate and the subsequent removal of the benzyl group produced water-soluble polymers containing zwitterionic hydroxamate groups and free pyridine (or imidazole) groups. The zwitterionic hydroxamate was a nucleophile more than 10 times as effective as simple hydroxamate anions, and the acetyl hydroxamate intermediate was efficiently hydrolyzed by the intrapolymeric pyridine (or imidazole) group. Thus, the catalytic efficiency of these bifunctional polymers was much better than monofunctional polymers which contain either hydroxamate or imidazole, and amounted to 10-20% of that of alpha -chymotrypsin under a comparable condition.