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.