Model copolymerization reactions: determination of the relative rates of addition of styrene and acrylonitrile to the benzyl radical

Reductive demercuration of benzylmercuric chloride in CH_2Cl_2 solutions affords toluene and as major products in a ratio of ca. 4:3. In similar solutions that contain styrene and acrylonitrile, obtains not only toluene and bibenzyl but also 1,3-diphenylpropane (ll), 1,2,4-triphenylbutane (12), 4-phenylbutyronitrile (13), and 2-benzyl-4-phenylbutyronitrile (14). Each of these products can be rationalized the basis of a reaction scheme in which addition of the benzyl radical to styrene or acrylonitrile is followed trapping of the adduct by transfer of a hydrogen atom or a benzyl fragment. The product ratios 11:12 13:14 were found to be independent of reaction conditions within the range of conditions employed in work. The relative rates of addition of styrene and acrylonitrile (k_s/k_A) were determined by analysis relative product yields as a function of the relative starting concentrations of styrene and acrylonitrile. find k_s/k_A = 0.33 ± 0.04, a result that is consistent with the known selectivity of the 1-phenylethyl radical that falls within the range of published reactivity ratios for styrene in its copolymerization with acrylonitrile. results support the use of the mercury method as a source of simple, reliable models for the macroradicals in the growth of copolymer chains.