Electron spin resonance spectra of carboxylic acid radical anions at 77°K

Abstract

Sodium atoms have been deposited on a series of monocarboxylic acids, R—COOH, at 77° K in the rotating cryostat and the deposits examined by electron spin resonance (e.s.r.) spectroscopy. The spectra show that the primary paramagnetic species in each case is the corresponding radical O– anion, [graphic omitted]. The spectra are similar to those observed for the primary radicals formed by X-, β- or γ- irradiation of mono-or di-carboxylic acids at 77° K and thus confirm that these radicals are the radical anions, and not cations, of the corresponding acids. The carbon-13 hyperfine coupling constants have been determined for the radical anion, [graphic omitted], of fully deuterated acetic acid. The results show that the free valence centre has a pyramidal configuration, in contrast to the planar structure found in many alkyl radicals.