Determination of Reactivity by MO Theory (). MO Studies of Substituent Effects of Rates of Phenylthiyl Radical Additions to -Methylstyrene

摘要

The addition of thiophenol to ￥á-methylstyrene has been studied MO theoretically using CNDO/2 method. Although overall reaction proceeds in two steps i.e., (1) decomposition of thiophenol to give phenylthiyl radical and (2) addition of the radical to ￥á-methylstyrene to give a new monomer radical, theoretical results suggested that the phenylthiyl radical formation step, (1), was the dominant process in determining the rate of addition; this was the rationale behind the negative ￥? value obtained experimentally from the Hammett plots for substituents on the thiyl radicals. The departure from a linear Hammett plot for addition of p-chlorophenylthiyl and m-trifluoromethyl phenylthiyl to p-methoxy-￥á-methylstyrene could be explained as a result of an increased contribution of the addition step, (2) to the overall reaction rate.