Substituent effects on benzyl radical hyperfine coupling constants. Part 2. The effect of sulphur substituents

Abstract

Several 4-substituted benzyl radicals of the general form R(O_n)SC₆H₄CH₂•(n = 0, 1, 2; R = Me, Ph, Tol, COCH₃ OCH₃) have been investigated by electron spin resonance (esr) spectroscopy. In general, the ability to delocalize spin density onto the substituent decreases as n increases. The effect of R on the spin density depends on the oxidation state of the sulphur. These trends are explained by considering the sulphur to be either a spin donor or a spin acceptor, depending on the oxidation state. The σ^•_α values are determined.