The michaelisߝmenten-type hydrolysis of an anionic phenyl ester by partly quaternized poly(1-vinyl-2-methylimidazole) and its copolymers

The catalytic hydrolysis of 3-nitro-4-acetoxy-benzoic acid was carried out mainly at 30°C, pH 8.0 in 1.0-M aqueous KCl. The polymer catalysts used were prepared by partial quaternization of the homopolymer and copolymers of 1-vinyl-2-methylimidazole with methyl iodide. Michaelis–Men ten kinetics were observed for all the catalysts, reaction constants being K_m=3–12 mM and k_cat=0.01–0.002 min⁻¹. Both K_m and k_cat values were maximal when the extent of quaternization of MVI polymer was 5–20%. This was probably attributable to the conformational change of the catalytic site in this region. Otherwise, the catalytic activity was explicable in terms of hydrophobic and electrostatic interactions between catalyst and substrate. In the partly quaternized polymers, the binding capacity and the intracomplex reactivity, in general, were increased or decreased simultaneously by varying the polymer composition. However, the binding and intracomplex reaction were compensatory in the case of uncharged polymer catalysts.