Electron spin resonance studies. Part 71. Side-chain oxidation pathways in the reactions of ˙OH and SO4–˙ with some phenyl-substituted carboxylic acids, their anions, and some related compounds

Abstract

A series of arene radical-cations has been generated in situ by the reactions of methylbenzene, phenylethanoic acid, 3-phenylpropanoic acid, and some derivatives and cyclic analogues with both SO₄ ^–˙ and ˙OH (the latter in acid solution). The results are interpreted in terms of a variety of subsequent rapid reactions including hydration, deprotonation (to give benzylic radicals), and fragmentation (decarboxylation): for a series of radical-zwitterions ⁺˙Ar(CH₂)_nCO₂ ^–(n= 1–3) decarboxylation (k 10⁹ dm³ mol^–1 s^–1) appears to proceed via direct intramolecular electron-transfer, though in some cases formation of a discrete σ-bonded intermediate cannot be ruled out.