Optical rotatory dispersion and circular dichroism. Part LXXII. (2R)-Mercaptopropionic acid and related compounds

Abstract

C.d. curves have been recorded for (2R)-mercaptopropionic acid and related compounds, including disulphides, and derivatives containing an acetylthio- or benzoylthio-chromophore. The curves for S-alkylmercaptopropionic acids and esters each show a maximum at 238 nm corresponding to the n→σ* transition of the sulphur atom and an additional small maximum at 271 nm which may be attributed to a less-stable conformer in which coupling occurs between the carboxy-chromophore and a non-bonding orbital of the hetero-atom. There is a very large percentage increase in Δε at low temperature, consistent with the flexibility of the acyclic molecules.