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.
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.
Nakanishi
Ikuo
I
Redox Regulation Research Group, Research Center for Radiation Safety, National Institute of Radiological Sciences, Inage-ku, Chiba 263-8555, Japan. nakanis@nirs.go.jp
Miyazaki
Kentaro
K
Shimada
Tomokazu
T
Iizuka
Yuko
Y
Inami
Keiko
K
Mochizuki
Masataka
M
Urano
Shiro
S
Okuda
Haruhiro
H
Ozawa
Toshihiko
T
Fukuzumi
Shunichi
S
Ikota
Nobuo
N
Fukuhara
Kiyoshi
K
D000838:Anions; D002839:Chromans / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy; D004583:Electrons; D005609:Free Radicals; D007700:Kinetics; D008956:Models, Chemical; D010100:Oxygen / Q000737:chemistry*; D019800:Phenol / Q000737:chemistry*; D013053:Spectrophotometry; D013481:Superoxides / Q000737:chemistry; D013696:Temperature; D014810:Vitamin E / Q000737:chemistry*
C048427:2,2,5,7,8-pentamethylchroman; D000838:Anions; D002839:Chromans; D005609:Free Radicals; D013481:Superoxides; D014810:Vitamin E; D019800:Phenol; D010100:Oxygen