“…Steric repulsion of substituents can cause the k, to decrease which would increase the kdlk,, all other factors remaining constant. At room temperature, the most reliable k, measurements show a decline in kc's with increasing halogenation with Cl's having a much greater effect than fluorine; 3.6 X 10'" M -' s -' for two CH3 radicals [21,22], 0.5 X lo1" M-ls-' and 1.4 X 10"' M-ls-' f or two CF3 radicals [23,24], <0.6 X 10'" M-'s-I for CH3 + CC13 radicals [25] and 0.2 X 10'' M-'s-' for CC13 radicals [27]. The smaller k,.…”