11. Interfacial Mechanism and Kinetics of Phase-Transfer Catalysis

FIG. 5Mechanism of the triphasic reaction (a) and the swollen type of resin (b).the substitution reaction of potassium acetate and benzyl bromide using 18-crown-6 asthe catalyst under solid–liquid PT conditions. This phenomenon of high conversion andproduct yield using SLPTC promotes more research work in investigating this type ofreaction.The most important step in PT-catalyzed reactions is that the catalyst must have theability to transfer the reacting anion into the organic phase to react with the organicsubstrate. In an aqueous–organic two-phase system, the reacting nucleophile is locatedin the aqueous phase and is usually insoluble or slightly soluble in the organic phase underthe operating conditions. In the situation of the absence of water, the anion nucleophileshould be given by the solid salt reactant, such that the unfavorable side reaction isprobably inhibited. In addition, SLPTC can promote the weak nucleophiles, such assalts of acetate, to have much higher reactivity by eliminating the hydrolysis effect.Hence, for SLPTC, it has the advantages of easy separation of products from reactants,easy selection of organic solvents, easy recovery of catalysts, the inhibition or preventionof unfavorable side reactions, etc., and shows great potential for commercial applicationsCopyright © 2003 by Taylor & Francis Group, LLC