Publication costs assisted by the University of Alberta Arrhenius parameters have been measured for the hydrogen transfer reactions of methyl radicals with silane, methylsilanes, and their deuterated counterparts. The A factors all lie in the range of log A = 11.4 12.4 and the activation energies do not follow the trends in the Si-H bond energies. The bond-energy-bondorder method of estimating the potential energies of activation cannot be directly applied to these reac-

Publication costs assisted by the University of Alberta Arrhenius parameters have been measured for the hydrogen abstraction reactions of the ethyl radical with silane, silane-dé, disilane, and disilane-de and for the reactions of the re-propyl and isopropyl radicals with silane and silane-dé molecules. The A factors exhibit little variation and the activation energies follow the trend predicted by BEBO calculations only if it is assumed that the combination-disproportionation reactions of these radicals possess a small activation energy, ~3.6 kcal/mol for the ethyl, repropyl, and the isopropyl radicals.

. Can. J. Chem. 52,3158 (1974). The thermal decomposition of ,-, where x = 0-3) is described by the reactionThe Arrhenius parameters for the series of silanes studied are as follows:

Variational transition state theory calculations of the reaction rates of F with H2, D2, and HD and the intermolecular and intramolecular kinetic isotope effects Primary and secondary kinetic isotope effects for the reactions of trifluoromethyl radicals with SiH, and SiD, have been calculated within the framework of transition-state theory using a complete nineatom model for the activated complex. The effect of variation of the applied force field has been investigated. Comparison of the results with the experimentally measured values suggests the occurrence of quantum mechanical tunneling in the reactions.

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