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 mediumElectronic supplementary information (ESI) available: the cyclic voltammogram of 1? and the experimental EPR spectrum of 1? with the computer simulation spectrum. See http://www.rsc.org/suppdata/ob/b3/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.

Electron-transfer mechanism in radical-scavenging reactions by a vitamin E model in a protic medium

“…In protic media, such as alcohols and water, 1H may be in equilibrium with the corresponding phenolate anion 1 − , which is a much stronger electron donor as compared to the parent 1H. 20 In such a case, 1 − may act as an electron donor rather than the parent 1H in MeOH.…”

Scavenging of dpph• Radicals by Vitamin E Is Accelerated by Its Partial Ionization: the Role of Sequential Proton Loss Electron Transfer

“…The SPLET mechanism has been independently discovered by Foti et al Moreover, the phenolate anion of the vitamin E model compound, PMHC (Figure ), has been shown to react with a dpph • more rapidly than its parent phenol …”

Electrochemistry of phenol in bis{(trifluoromethyl)sulfonyl}amide ([NTf2]−) based ionic liquids

“…(3) has also been proposed for the reaction of the phenolate anion of a vitamin E model with molecular oxygen in an aprotic medium [22]. Scheme 1 illustrates a potential mechanism by which the phenoxy radical can react with the [NTf 2 ] À anion to form the phenyl triflate derivative.…”