Interpretation of the Electron-Spin Resonance Spectrum of the Methyl Radical

A valence-bond calculation of the proton hyperfine splitting in the electron-spin resonance spectrum of the methyl radical has been performed. The splitting was computed as a function of the angular configuration of the molecule. For the planar radical a splitting of 27±5 gauss was found, in agreement with experimental measurements on irradiated solids. However, the functional dependence of the splitting on angular configuration and the uncertainty in certain of the molecular integrals are such that deviations from planarity of 10–15° cannot be definitely excluded.