A wide range of thiols have been exposed to ⁶⁰Co γ-rays at 77 K both in the pure state and in dilute methanolic or aqueous glasses. Spectra assigned to RS· radicals had g_z values (z is along the C–S bond) which varied with the environment, but which were all close to 2.158 in methanol. Dissociative electron capture at sulphur (RSH + e^–→ R·+ SH^–) was only observed in methanolic or aqueous glasses, and it is postulated that solvation of the ejected SH^– ion plays an important role. The structure of a species (X) containing two sulphur atoms and having g values close to 2.058, 2.025, and 2.001 is discussed. Two rival structures, RS·–SR₂ and RSS· are considered in depth and it is concluded that the former is most probable unless both species have very similar properties. Electron loss to give RSH⁺ followed by reaction to give R(H)S·–S(H)R⁺ cations is postulated to explain certain features in the e.s.r. spectra, as an alternative to proton loss to give RS· radicals.

Various organic sulphides, including dimethyl and di-t-butyl sulphide and methionine, together with disulphides, including dimethyl and dibutyl disulphides, cystine and lipoic acid have been exposed to ⁶⁰Co γ-rays at 77 K, both in the pure state and in various solvents. E.s.r. and, in selected cases, optical spectra of the resulting intermediates are reported and discussed. In particular, the reaction R₂S˙⁺+ R₂S → R₂S–SR₂ ⁺ is considered and it is suggested that certain species, previously identified as R₂S˙⁺, are better identified as R₂S–SR₂ ⁺. The structure of species having g values close to 2.058, 2.025, and 2.001 is also discussed.

A range of mono-, di-, and tri-alkyl phosphates have been exposed to ⁶⁰Co γ-rays at 77 K and at ambient temperature, together with their solutions in CD₃OD at 77 K. Monoalkyl phosphates (as the sodium, potassium, magnesium, or calcium salts) gave alkyl radicals on electron capture at 77 K, but a low yield of ·PO₃ ^2– was detected after irradiation at ambient temperature. The major electron loss centre was formed by loss of α-hydrogen (R₂ĊOPO₃ ^2–). In general, the ³¹P hyperfine coupling for these radicals was in the range 0–10 G, but for the radical MeĊHOPO₃ ^2– in the calcium salt a coupling of 45 G indicated considerable hyperconjugative interaction. Dialkyl phosphates gave the phosphoryl radicals ROPO₂ ^– on irradiation at 77 K, together with alkyl radicals. Some sodium and potassium salts also gave relatively low yields of the parent anions, (RO)₂PO₂ ^2–(phosphoranyl radicals). These were not obtained from CD₃OD solutions, but the phosphoryl radicals and alkyl radicals were detected. Only phosphoryl radicals were obtained on irradiation at ambient temperature. The major electron-loss centres were again R₂ĊOPO₂(OR)^–. Trialkyl phosphates at 77 K gave predominant yields of the parent phosphoranyl anions, (RO)₃PO^–, although phosphoryl radicals were also detected. On annealing, there was no evidence for the conversion of phosphoranyl radicals into phosphoryl radicals. Solutions in CD₃OD gave the same species, but the phosphoryl radicals were obtained in relatively greater yields. Again, the major electron-loss centres seemed to be R₂ĊOPO(OR)₂ radicals. A doublet species having A∥ 237 and A⊥ 179 G was also obtained from MeOPO₃Na₂, MeOPO₃Mg, and other methyl esters after irradiating at 77 K and slight annealing. In some cases, an extra 8 G splitting was observed on these features. Possible structures for this species are discussed.