Electron spin resonance studies. Part 69. Oxidation of some aliphatic carboxylic acids, carboxylate anions, and related compounds by the sulphate radical anion (SO4–˙)

Abstract

The results of e.s.r experiments involving in situ photochemical generation of the sulphate radical anion in the presence of some aliphatic carboxylic acids and their anions are interpreted in terms of attack at the carboxy group (to give alkyl radicals via decarboxylation) and hydrogen-atom abstraction from carbon atoms in the chain. The general order of reactivity of different sites is CO2– > β-H, γ-H, etc. > CO2H > α-H. For example, reaction with EtCO2H gives ˙CH2CH2CO2H (k 2 × 105 dm3 mol–1 s–1) and Et˙(k 7 × 104 dm3 mol–1 s–1). Radicals formed by abstraction of α-H (e.g.˙CH2CO2H from ethanoic acid) are shown to result usually from further reactions of first-formed alkyl radicals. The reactions of SO4–˙ with some amides, nitriles, and esters have also been investigated.