Electron spin resonance and electron nuclear double resonance studies of cation radicals derived from tocopherol model compounds

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

• Publisher: Elsevier Science
• Year: 1984
• Tongue: English
• Weight: 385 KB
• Volume: 35
• Category: Article
• ISSN: 0009-3084
• DOI: 10.1016/0009-3084(84)90046-x

✦ Synopsis

Electron spin resonance (ESR) and electron nuclear double resonance (ENDOR) measurements were performed for the cation radicals obtained from the model compounds of c~-, #-, 3'and 6-tocopherol (vitamin E) by oxidizing the tocopherol precursors in an AICI3-CHaCI a solution. The proton hyperfine coupling constants and g-values were precisely determined. The ENDOR spectra of the cation radicals of a-, g-, 3'-and 6-tocopherol models in CH:CI 2 at -100°C clearly show 10, 6, 6 and 12 different proton hyperfine couplings, respectively. By varying the temperature, the ESR spectra of the a-and 6-tocopherol model cations exhibit line-width alternation phenomena characteristic of the hindered rotation of the OH group. However, neither the t3-nor the 3"-to~pherol model cation radical ESR spectra show any sign of an alternating line-width effect. These results are interpreted by assuming that the fl-and 7tocophelol model cations are stabilized in the trans and cis conformations, respectively. On the other hand, both the a-and 6-tocopherol model cations exist as cis and trans isomers.