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

Org Biomol Chem. 2003 Nov 21;1(22):4085-8. doi: 10.1039/b306758k.

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.

MeSH terms

  • Anions
  • Chromans / chemistry
  • Electron Spin Resonance Spectroscopy
  • Electrons
  • Free Radicals
  • Kinetics
  • Models, Chemical
  • Oxygen / chemistry*
  • Phenol / chemistry*
  • Spectrophotometry
  • Superoxides / chemistry
  • Temperature
  • Vitamin E / chemistry*

Substances

  • 2,2,5,7,8-pentamethylchroman
  • Anions
  • Chromans
  • Free Radicals
  • Superoxides
  • Vitamin E
  • Phenol
  • Oxygen