Effect of copolymers of 4(5)-vinylimidazole and quaternary imidazolium salts on the hydrolysis rates of charged and neutral esters. II

Abstract

The effects of copolymeric catalysts containing hydrophobic binding sites (quaternary imidazolium salts) and catalytically active nucleophilic sites (imidazole) on the hydrolysis of long-chain anionic esters were investigated. The quaternary imidazolium salt groups contained hydrocarbon chains of varying length. Their solubility relationships and viscosity measurements followed a trend governed by the hydrocarbon chain length of the quaternary imidazolium salt. These investigations revealed that increasing the hydrocarbon chain length of the quaternary imidazole groups along the copolymer chain or the chain length of the ester substrate resulted in an increase of the catalytic rate of ester hydrolysis. Increasing the ethanol content decreased the catalytic activity and greatly reduced the apolar binding between the catalyst and substrate. For the cases of low ethanol content and high chain length of the substrate, the ester hydrolysis reactions in the presence of the copolymeric catalysts preceeded by a Michaelis-Menten kinetic scheme.