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

• Published in: Organic & biomolecular chemistry Vol. 1; no. 22; p. 4085
• Main Authors: Nakanishi, Ikuo, Miyazaki, Kentaro, Shimada, Tomokazu, Iizuka, Yuko, Inami, Keiko, Mochizuki, Masataka, Urano, Shiro, Okuda, Haruhiro, Ozawa, Toshihiko, Fukuzumi, Shunichi, Ikota, Nobuo, Fukuhara, Kiyoshi
• Format: Journal Article
• Language: English
• Published: England 21-11-2003
• Subjects: Anions; Chromans - chemistry; Electron Spin Resonance Spectroscopy; Electrons; Free Radicals; Kinetics; Models, Chemical; Oxygen - chemistry; Phenol - chemistry; Spectrophotometry; Superoxides - chemistry; Temperature; Vitamin E - chemistry
• ISSN: 1477-0520
• DOI: 10.1039/b306758k

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.