Spectroscopic and Related Properties of Thiols

Spectroscopic and Related Properties of Thiols.— The n.m.r. absorption of the thiol proton moves to lower field in the order PhCHa SH, PhjCH SH, PhaC SH corresponding hydrotrisulphides RSS SH show the opposite sequence, due to over-riding inductive and anisotropic effects within the cumulative sulphur chain. 

The ultraviolet c.d. of 2-(iJ)-mercaptopropionic acid is dominated by the n IT Cotton effect (near 220 mn) of the carboxy-group, while the S -methyl homologue shows, in addition to the positive n r thioether Cotton effect at 238 nm, a weak negative c.d. maximum at 271 nm, ascribed to electrostatic coupling of the carboxyl and thioether transitions.  

Kawamura, T. Horii, and J. Tsurugi, Bull. Ghent. Soc. Japan, 1971, 44, 2878. 

Pulse radiolysis of penicillamine in aqueous solution gives thiyl radicals RS% Amax 330 nm, and the radical anion RSSR-, Amax 450 nm, formed from RS and RS / Photolysis of propanethiol tritiated at SH, in the presence of a hydrogen donor, results in tritium scrambling in the propyl group and in the hydro n donor, suggesting that such a system is a useful source of H atoms in solution. In eased yields of the products of sensitized photodecarboxylation of R X CHj COaH (X = O, S, or NH) are obtained in the presence of thiophenol as hydrogen donor. Butane-thiol quenches triplet acetophenone only slowly (At = 1.4 x 10 1 mol s ), and it can be included in the reaction systems of ketone photo-reactions as a radical trap without interfering with the photo-excited substrate.  

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