Kinetic study of the electron-transfer oxidation of the phenolate anion of a vitamin E model by molecular oxygen generating superoxide anion in an aprotic medium

Abstract

Electron-transfer reduction of molecular oxygen (O₂) by the phenolate anion (1⁻) of a vitamin E model, 2,2,5,7,8-pentamethylchroman-6-ol (1H), occurred to produce superoxide anion, which could be directly detected by a low-temperature EPR measurement. The rate of electron transfer from 1⁻ to O₂ was relatively slow, since this process is energetically unfavourable. The one-electron oxidation potential of 1⁻ determined by cyclic voltammetric measurements is sufficiently negative to reduce 2,2-bis(4-tert-octylphenyl)-1-picrylhydrazyl radical (DOPPH˙) to the corresponding one-electron reduced anion, DOPPH⁻, suggesting that 1⁻ can also act as an efficient radical scavenger.