Heterogeneous Polymeric Catalysts: Their Synthesis And Esterolytic Reactions (imidazole, Polystyrene).

Abstract

Heterogeneous insoluble catalysts were prepared by grafting nucleophilic imidazole groups onto a crosslinked polystyrene resin and their esterolytic activity toward the solvolysis of 3-nitro-4-acyloxybenzoic acid substrates in aqueous ethanol solutions was investigated. A continuous flow stirred batch reactor was developed and used to produce reproducible data successfully in this kinetic study. The thermodynamic parameters, isokinetic relationship, and isoequilibrium relationships were investigated. The overall rates of solvolysis of S(,n)('-) substrates catalyzed by heterogeneous catalysts were compared with the reactions catalyzed by monomeric imidazole. The hydrophobic effects of substrates with long side chains, saturation phenomena due to the formation of catalyst-substrate complexes, and rate enhancements induced by the heterogeneous catalysts in water-ethanol solvent were investigated. Such variables as temperature, pH, solvent composition and crosslinking density were also studied.