PHASE-TRANSFER CATALYSIS IN SUPERCRITICAL CARBON-DIOXIDE - KINETIC AND MECHANISTIC INVESTIGATIONS OF CYANIDE DISPLACEMENT ON BENZYL-CHLORIDE

This work reports the first studies designed to examine the detailed m echanism of a phase-transfer catalyzed reaction between a supercritica l CO2 phase and a solid salt phase. The nucleophilic displacement of b enzyl chloride with potassium cyanide to form phenylacetonitrile and p otassium chloride was carried out with a tetraheptylammonium salt as t he phase-transfer catalyst, The effects of various reaction variables on the kinetics were investigated, including the amount of catalyst, t he amount of potassium cyanide, the presence of acetone cosolvent, and temperature. The kinetic data, along with catalyst solubility measure ments, indicate that. the operating reaction mechanism is a three-phas e system consisting of a supercritical CO2 phase, a catalyst-rich phas e, and a solid salt phase and that the reaction actually occurs in the catalyst-rich phase. Further, the reaction mechanism was investigated with two additional phase-transfer catalysts, 18-crown-6 and poly(eth ylene glycol), and these results are consistent with the postulated th ree-phase mechanism.