Free radical addition to olefins. Part 12. - Addition of bromodifluoromethyl radicals to fluoroethylenes

The kinetics of the photochemical addition of dibromodifluoromethane to vinyl fluoride, 1,1-difluoroethylene and tetrafluoroethylene has been examined in gas phase experiments. The mechanism involves the addition of CF ₂Br· radicals to the alkene in a chain reaction. In the accessible range of alkene concentrations the chains are terminated not only by dimerization of the CF₂Br· radicals but also by cross-terminations involving CF₂Br· radicals and adduct radicals. Relative rate constants and Arrhenius parameters for the addition of CF₂Br· radicals to specific sites in the alkenes have been measured from competitive experiments with ethylene. An estimate of the absolute Arrhenius parameters for the addition of CF₂Br· radicals to ethylene is also given.