Issue 4, 2005
From the journal:

Organic & Biomolecular Chemistry

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

Ikuo Nakanishi,*ab   Tomonori Kawashima,ac   Kei Ohkubo,b   Hideko Kanazawa,c   Keiko Inami,d   Masataka Mochizuki,d   Kiyoshi Fukuhara,e   Haruhiro Okuda,e   Toshihiko Ozawa,a   Shinobu Itoh,f   Shunichi Fukuzumi*b  and  Nobuo Ikota*a  

* Corresponding authors

a Redox Regulation Research Group, Research Center for Radiation Safety, National Institute of Radiological Sciences, Inage-ku, Chiba, Japan
E-mail: nakanis@nirs.go.jp
Fax: +81-43-255-6819
Tel: +81-43-206-3131

b Department of Material and Life Science, Graduate School of Engineering, Osaka University, SORST, Japan Science and Technology Agency (JST), Suita, Osaka, Japan

c Department of Physical Pharmaceutical Chemistry, Kyoritsu University of Pharmacy, Minato-ku, Tokyo, Japan

d Division of Organic and Bioorganic Chemistry, Kyoritsu University of Pharmacy, Minato-ku, Tokyo, Japan

e Division of Organic Chemistry, National Institute of Health Sciences, Setagaya-ku, Tokyo, Japan

f Department of Chemistry, Graduate School of Science, Osaka City University, Sumiyoshi-ku, Osaka, Japan

Abstract

The scavenging reaction of 2,2-diphenyl-1-picrylhydrazyl radical (DPPH˙) or galvinoxyl radical (GO˙) by a vitamin E model, 2,2,5,7,8-pentamethylchroman-6-ol (1H), was significantly accelerated by the presence of Mg(ClO4)2 in de-aerated methanol (MeOH). Such an acceleration indicates that the radical-scavenging reaction of 1H in MeOH proceeds via an electron transfer from 1H to the radical, followed by a proton transfer, rather than the one-step hydrogen atom transfer which has been observed in acetonitrile (MeCN). A significant negative shift of the one-electron oxidation potential of 1H in MeOH (0.63 V vs. SCE), due to strong solvation as compared to that in MeCN (0.97 V vs. SCE), may result in change of the radical-scavenging mechanisms between protic and aprotic media.

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

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Article information

DOI
https://doi.org/10.1039/B416572A
Article type
Paper
Submitted
11 Nov 2004
Accepted
29 Nov 2004
First published
11 Jan 2005

Org. Biomol. Chem., 2005,3, 626-629

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

I. Nakanishi, T. Kawashima, K. Ohkubo, H. Kanazawa, K. Inami, M. Mochizuki, K. Fukuhara, H. Okuda, T. Ozawa, S. Itoh, S. Fukuzumi and N. Ikota, Org. Biomol. Chem., 2005, 3, 626 DOI: 10.1039/B416572A

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