Free radical addition to olefins. Part 14.—Addition to trifluoromethyl radicals to fluoroethylenes

A competitive method has been used to determine the relative Arrhenius parameters for the addition of trifluoromethyl radicals to specific sites in fluoroethylenes taking the addition to one end of ethylene as standard.[graphic omitted]The relative activation energies correlate well with those for the addition of other halogenoalkyl radicals to the same olefins. The A-factors have been calculated from absolute rate theory using two models of the transition state, one resembling the products and the other resembling the reactants. Comparison of the calculated and experimental A-factors suggests that formation of the bond between the trifluoro-methyl radical and the alkene has proceeded sufficiently far, in the transition state, to cause significant breaking of the alkene double bond.