Electron nuclear double resonance studies of radicals produced by the PbO2 oxidation of α-tocopherol and its model compound in solution

✍ Scribed by Kazuo Mukai; Noriko Tsuzuki; Kazuhiko Ishizu; Setsuhiro Ouchi; Kenji Fukuzawa

• Publisher: Elsevier Science
• Year: 1981
• Tongue: English
• Weight: 325 KB
• Volume: 29
• Category: Article
• ISSN: 0009-3084
• DOI: 10.1016/0009-3084(81)90078-5

✦ Synopsis

The electron nuclear double resonance (ENDOR) spectra of chromanoxyl radicals obtained t,y the PbO2 oxidation of ~-tocopherol and its model compound were observed in t-butylbenzene, and the proton hyperfine coupling constants were correctly determined. Each of the two #-and 3,-methylene protons in the chromanoxyl ring shows an equivalent hyperfine splitting, suggesting that the heterocyclic ring attached to the aromatic ring axe coplanar with the plane of the aromatic system. A comparison of the hyperfine couplings in c~-tocopheroxyl radical and its model shows that the introduction of a long-isoprenoid-chain in the c~-tocopherol in place of a methyl group in the model compound has very little effect on the unpaired spin distribution or molecular structure of the chromanoxyl skeleton. The results of McLachlan molecular orbital (MO) calculations were found to be in satisfactory agreement with the 'experimental' spin densities evaluated from the hyperfine coupling constants.