Reaction of polymeric radicals with organometallic compounds

Abstract

AbstractThe reactivities of polystyryl, polymethyl methacrylyl and polyacrylonitryl radicals with thirteen organometallic substrates were measured and correlated at 60°C. The organometallics chosen were saturated, aliphatic derivatives of elements from Groups 2b, 3a, 4a, and 5a of the Periodic Table. Correlation was accomplished by the method proposed by Bamford, Jenkins, and Johnston. The correlation based on the above three monomers allowed the prediction of the chain transfer constant C of four of the tested substrates with an untested radical, the polymethyl acrylyl, with an accuracy of better than 101. Since the correlation was based on absolute values of C which covered the range of 106 and which were accurate to within 100.8, it was concluded that the correlation was a valid one and was useful for predictive purposes. Values of C for untested substrates can be predicted with only a low order of accuracy because data are not available on the polarizability of most compounds. The introduction of oxygen into the vicinity of the metal–carbon bond reduces the values of C drastically and confirms that C is very sensitive to polar factors. There appears to be a correlation between β (the polarizability of the substrate) and β (the intrinsic reactivity of the substrate) within a given group of the Periodic Table. The fact that there is not a general correlation between α and α for the whole Periodic Table suggests that the mechanism of the transfer reaction is different from group to group.