Electron spin resonance studies. Part XL. A kinetic investigation of the oxidation of oxygen-substituted carbon radicals by hydrogen peroxide

Abstract

E.s.r. spectroscopy has been employed to investigate the reaction of the hydroxyl radical with some alcohols and ethers, and the oxidation of hydroxy- and alkoxy-conjugated radicals by hydrogen peroxide. The Ti^III–H₂O₂ couple has been used to generate radicals, and application of a competitive kinetic method involving the steady-state approximation leads to the estimation of rate constants for some of these reactions. For example, reaction of diethyl ether with ·OH leads to the radicals ·CHMeOEt and ·CH₂CH₂OEt; the observed steady-state concentrations at low [H₂O₂] are in the ratio ca. 13 : 1. At higher concentrations of hydrogen peroxide, this ratio is reduced and we estimate that the rate constant for oxidation of ·CHMeOEt by H₂O₂ is 5·5 × 10⁴ l mol^–1 s^–1. The influence of structural features on the oxidation of related radicals has been investigated. Evidence is also presented for oxidation and reduction processes involving radicals generated during the oxidation of 2-methoxyethanol in aqueous solution.