On the Relations between ESR-Hyperfine Splittings and Spin Densities in Simple Substituted Alkyl Radicals

Abstract

A simple treatment of spin densities and ESR-coupling constants of substituted alkylradicals is developed. It is shown that the spin densities ρ_a in the α-carbon 2 p_z-functions may be calculated by use of a product rule from substituent parameters 1 (X_i). Furtheron it is found, that the parameters Q in the well known relations a = Q-ρ_a are unique constants for rotating methylgroups, whereas for α-protons they depend on the electron withdrawing forces of the substituents. Values of Δ (X_i) and QH_H ^CH are tabulated and discussed. The ESR-coupling constants of four new transient alkyl radicals are also given.