Primary Photochemical Products of Dithioglycolic Acid in Aqueous Solution

Abstract

Abstract— The photochemistry of dithioglycolic acid at 254 nm was investigated in deaerated aqueous solutions in the pH range 1.4–7.3. Initial yields of the primary photochemical products H2S,–SH and aldehyde‐(probably glyoxylic acid) were determined. The complex pH dependence of these simultaneously formed first stable products is interpreted in terms of the ground‐state ionic equilibria, and in addition pH‐dependent processes occurring in the excited state and labile intermediate sequence. It is suggested that the photochemical mechanism involves two parallel pathways: one a hydrolytic splitting of S ‐ S leading to H2S formation (unaffected by the presence of O2 or isopropanol), the other a free radical mechanism via C–S breakage, which is affected by the presence of O2 or isopropanol.

The Photolysis of Penicillamine Disulphide in Acidic Aqueous Solution

“…It is, therefore, most unlikely that thiol has radical precursors. Feitelson et al (1973) obtained evidence for a non-radical mechanism for thiol production in the photolysis of dithiodiacetic acid. However, their proposed hydrogen atom transfer to form a thiol and Irercapto-acid is not possible in the case of penicillamine disulphide where the methylene hydrogens are substituted with methyl groups.…”