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Published January 1989 | public
Journal Article

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

Abstract

Reductive demercuration of benzylmercuric chloride in CH_2Cl_2 solutions affords toluene and bibenzyl as major products in a ratio of ca. 4:3. In similar solutions that contain styrene and acrylonitrile, one 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 on the basis of a reaction scheme in which addition of the benzyl radical to styrene or acrylonitrile is followed by trapping of the adduct by transfer of a hydrogen atom or a benzyl fragment. The product ratios 11:12 and 13:14 were found to be independent of reaction conditions within the range of conditions employed in this work. The relative rates of addition of styrene and acrylonitrile (k_s/k_A) were determined by analysis of relative product yields as a function of the relative starting concentrations of styrene and acrylonitrile. We find k_s/k_A = 0.33 ± 0.04, a result that is consistent with the known selectivity of the 1-phenylethyl radical and that falls within the range of published reactivity ratios for styrene in its copolymerization with acrylonitrile. These results support the use of the mercury method as a source of simple, reliable models for the macroradicals involved in the growth of copolymer chains.

Additional Information

© 1989 American Chemical Society. Received March 25, 1988. Acknowledgment is made to the donors of the Petroleum Research Fund, administered by the American Chemical Society, for support of this work. Support of our research programs by a Presidential Young Investigator Award of the National Science Foundation is also gratefully acknowledged. NMR spectra were recorded in the University of Massachusetts NMR Laboratory, which is supported in part by the NSF Materials Research Laboratory at the university. Registry No. 1,3-Diphenylpropane, 1081-75-0; 1,3-di- (12) phenlacetone, 102-04-5; 1,3,4-triphenyl-2-butanone, 62640-72-6; benzyl bromide, 100-39-0; 1,2,4-triphenylbutane9 116374-60-8; 2-benzyl-4-phenylbutyronitrile, 89873-50-7; hydrocinnamonitrile, 645-59-0; 2-(bromoethyl)benzene, 103-63-9; styrene, 100-42-5; acrylonitrile, 107-13-1; 4-phenylbutyronitrile, 2046-18-6; benzylmercuric chloride, 2117-39-7.

Additional details

Created:
August 19, 2023
Modified:
October 19, 2023