DEUTERIUM KINETIC ISOTOPE EFFECTS AND THEIR TEMPERATURE-DEPENDENCE INTHE GAS-PHASE S(N)2 REACTIONS X(-)-]CH(3)X+Y- (X, Y=CL, BR, I)(CH3Y)

Extended-basis-set calculations with electron correlation have been ca rried out for the reactant and transition state properties of the gas- phase S(N)2 reactions Cl- + CH3Br --> CH3Cl + Br-, Cl- + CH3I --> CH3C l + I-, and Br- CH3I --> CH3Br + I-. The resulting force fields are us ed for canonical unified statistical theory calculations of the rate c onstants of these reactions and their perdeuterated analogs. Kinetic i sotope effects (KIEs) and their temperature dependences have been calc ulated and analyzed, and they are compared to available experimental d ata. We find only small deviations of the generalized transition state theory results from conventional transition state theory, and we obta in reasonable agreement (similar to 10%) with experimental results for the KIEs of the first two reactions, but the KIEs that we predict for the third reaction are up to 26% higher than experiment.