Solid-solid-liquid reaction systems. A mechanistic study

The mechanism of the alkylation of phenoxide with benzyl bromide, catalysed by polymer-bound phase-transfer catalysts, has been studied as a model for solid-solid-liquid reaction systems. A 'typical triphase catalyst' has been compared with a commercial ion-exchange resin. The reactions proceed by a mechanism which is similar to the extraction mechanism of classical phase-transfer catalysis. Depending on the reaction conditions, the reaction rates are either mass-transfer controlled or chemical-reaction controlled. In some cases the C/O-alkylation ratio is found to depend on the water content of the system. The possible mechanisms for the transport of the phenoxide ion to the catalytic site are discussed.