GAS-PHASE REACTIONS OF SILICON-CENTERED INTERMEDIATES WITH CHLOROFLUOROCARBONS

Pyrolysis of pentamethyldisilane in the presence of a CFC, dichlorodif luoromethane, efficiently replaced chlorine by hydrogen in the CFC, wi th concomitant formation of chlorosilanes. Although the primary interm ediate in this pyrolysis is dimethylsilylene, there was strong evidenc e that conversions resulted from reactions of organosilyl and alkyl ra dicals. Experiments to confirm this conclusion are described, and mech anisms are discussed. Two independent measurements of the activation e nergy difference between chlorine- and fluorine-abstraction from dichl orodifluoromethane by trimethylsilyl radicals gave concordant values o f 52 +/- 5 kJ mol(-1). The reactions described are of interest in rela tion to the environmental importance of dechlorinating CFCs.