Electron spin resonance spectra and hyperfine coupling constants of the α-tocopheroxyl and 2,2,5,7,8-pentamethyl-chroman-6-oxyl radicals derived from vitamin E and its model and deuterated model compounds

Highly resolved electron spin resonance spectra of the α-tocopheroxyl or 2,2,5,7,8-pentamethylchroman-6-oxyl radicals were obtained from the oxidation of α-tocopherol (vitamin E) or its model compound, 2,2,5,7,8-pentamethylchroman-6-ol, with 2,2-diphenyl-1-picrylhydrazyl or superoxide ion. Complete assignments of the hyperfine coupling constants of these radicals were made on the basis of the spectra of the deuterated isotopomers of the 2,2,5,7,8-pentamethylchroman-6-oxyl radical. The large coupling constant due to the methyl group at C-5 in the α-tocopheroxyl radical may have implications for the high reactivity toward radicals of C-5 in α-tocopherol.