Mechanism of phase-transfer catalysis using glycidyl methacrylate-ethylene dimethacrylate copolymers modified with tributylammonium groups in nucleophilic displacement reactions

Abstract

The kinetics of phase-transfer catalysis using glycidyl methacrylate-ethylene dimethacrylate resins modified with pendant quaternary butylammonium groups have been studied. In contrast to expectations based on currently proposed mechanisms, the activity of polymeric catalysts is not improved through modifications that balance the hydrophilic and hydrophobic properties of the material. It is believed that much of the activity of the polymeric catalysts derives from the swelling of the polymer in both aqueous and organic phases. This enhances not only the rate of diffusion of both reagents to the vicinity of the catalytically active groups but also the ability of reactive groups to oscillate between the two phases. Both swelling and diffusion are restricted severely as the percentage of crosslinking is increased. This restriction is of particular importance with macroporous resins. Comparison of kinetic data obtained with various polymers suggests that gel polymers with very small bead sizes and therefore high external surface areas provide much higher reactivities than their macroporous counterparts.