KINETICS OF CHLORINE-36 EXCHANGE REACTION BETWEEN GALLIUM CHLORIDE AND METHYL CHLORIDE . DIMETHYLCHLORONIUM ION AS A POSSIBLE INTERMEDIATE IN EXCHANGE REACTION

A kinetic study has been made of the chlorine-36 exchange reaction between gallium chloride and methyl chloride in excess methyl chloride. The reaction is second order in gallium chloride, with a second-order rate constant equal to 7.8 ± 0.6 × 10−4l. mol−1 min−1. From a comparison of the rate of chlorine exchange and methylation under identical conditions, it is concluded that the alkylation and exchange reactions cannot involve the same rate-determining intermediate. It is proposed that the mechanism for chlorine exchange involves the formation of the dimethylchloronium ion as an unstable intermediate. The applicability of this mechanism to other alkyl halide-metal exchange reactions is discussed. An equation is derived for homogeneous solution exchange reactions involving one volatile exchanging species. © 1969, American Chemical Society. All rights reserved.