Heterogeneous Acid-base Catalysis: Part 2—Catalysis of the Hydrolysis of Ethyl Vinyl Ether (ethoxyethene) by Methacrylic Acid-divinylbenzene Copolymer Weak-acid Ion Exchange Resins

Abstract

Methacrylic acid-divinylbenzene copolymer is a more powerful catalyst for the hydrolysis of ethyl vinyl ether than for the hydrolysis of dimethyl acetal. Comparison of the reactions indicates that for ethyl vinyl ether catalysis by undissociated carboxylic acid groups on the resin is the predominant effect. The variation of the observed catalytic constant with the degree of neutralisation of the resin is shown to be explicable on the assumption that carboxylic acid groups flanked by two undissociated carboxylic acid groups have a higher acidity and catalytic activity than those flanked by one or two (ionised) carboxylate groups. The corresponding local dissociation quotients are evaluated from titration curves by a simple application of the transfer matrix method for a chain. The entire kinetic analysis is based on the simple two-phase model of catalysis, but there are indications that gel diffusion effects may not be entirely absent in the case of this reaction