THE ELECTRON-SPIN RESONANCE SPECTRA OF SOME METHYLATED ANTHRASEMIQUINONES: EVIDENCE FOR RESTRICTED ROTATION

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Abstract
The hyperfine electron-spin resonance spectra of a number of methyl-substituted 9,10-anthrasemiquinones have been determined. The spectra have been analyzed by computer techniques, and splitting constants have been assigned for all protons. The results indicate that, while the parent quinones are essentially free of steric hindrance, the methyl groups in the α position of the reduced quinones are not free to rotate. The methyl groups in the β position of the semiquinones show normal hyperconjugative behavior. These results are consistent with the different redox potentials of these compounds revealed in a previous study.