Tadashi Mishina

ESR studies of Yang’s biradical

Yang’s biradical (I), its mono‐ and di‐deuterated derivatives, (II) and (III) were generated by PbO2 oxidation in toluene of corresponding bisphenol precursors and investigated by means of ESR spectroscopy. The frozen toluene ESR spectrum of Yang’s biradical (I) at 77 °K has been analyzed, and the g‐ and D‐tensor values have been determined. The results suggest that the threefold symmetry of Yang’s biradical has disappeared in the frozen rigid matrix. Essentially the same g‐ and D‐tensor values are observed for its mono‐ and di‐deuterated derivatives (II) and (III). On the other hand, the toluene solution ESR spectra of these three biradicals at 20 °C appear to correspond to hyperfine interaction with equivalent six, five, and four meta ring protons, respectively. The expected inequivalence of the proton splittings of these biradicals is less than the linewidths.

Nitration of fully methylated acylbenzenes and 1,3-diacylbenzenes bearing bulky acyl groups. Side-chain attack occurring exclusively on the methyl group at the most hindered site

On treatment with concentrated nitric acid, the title compounds undergo attack on the side-chain which occurs exclusively on the methyl group at the most hindered site, giving 6-acyl-2,3,4,5-tetramethylbenzyl nitrate, and 2,6-diacyl-3,4,5-trimethylphenylnitromethane and/or 2,6-diacyl-3,4,5-trimethylbenzyl nitrate as the respective major side-chain substitution products.