KINETICS OF GALLIUM CHLORIDE CATALYZED METHYLATION OF BENZENE IN EXCESS METHYL CHLORIDE

The kinetics of the reaction of methyl chloride with benzene and hexadeuteriobenzene, using methyl chloride as the solvent and gallium chloride as the catalyst, were determined at –35.6°, utilizing gas chromatography to follow the reaction. The reactions occur at the same rate and are first order in the aromatic and second order in gallium chloride. Product xylene isomerization was observed. The third-order rate constant decreases markedly with increasing reaction time from its zero-time value of 1.6 × 10−4I.2 mol−2 min−1. Disproportionate and catalytic inhibition due to σ-complex formation are suggested as causes of this effect. Data analysis eliminates disproportionation as its sole cause. Reaction mechanisms are proposed for alkylation in methyl chloride and 1,2,4-trichlorobenzene. © 1969, American Chemical Society. All rights reserved.