| Abstract: | Tert-butoxy radicals generated in the photolysis of di-tert-butyl peroxide in benzene at 25°C react with vinyl monomers by double-bond addition and, in most cases, also by competitive hydrogen abstraction. The rate constant for the double-bond addition changes by a factor of 17 between isoprene, which shows the highest reactivity, and the methacrylate derivatives, which are the least reactive of the monomers considered. The fraction of tert-butoxy radicals that react by hydrogen abstraction varies considerably with the monomer structure, ranging from 0.9 (cyclohexyl methacrylate) to less than 0.05 (styrene and conjugated diolefins). In the methacrylate derivatives, most of the hydrogen abstraction takes place, not in the α-methyl group, but in the alkyl chain. |
