ESR studies of alkyl aryl ketyl radicals

Abstract

Reactions of R1-substituted benzenecarboxylic acids (R1 = H, Me, Et, and t-Bu) with R2MgX (R2 = Et and n-Pr) in the presence of nickel produce ketyl radicals R1-Ar-CO.-R2. Average values of splitting constants of the protons in the aromatic nucleus are a2 = a6 = 0.48 mT, a4 = 0.53 mT, and a3, a5 < 0.12 mT. In some cases for R2 = n-Pr interaction of gamma protons is also observed with a2 = 0.04 mT. The investigated substituents R1, R2 have no marked influence on distribution of spin density of the unpaired electron.