Infra-red spectra of some organic sulphur-oxygen compounds

Infra-red spectra were obtained from anhydrous and hydrated sulphonic acids, as well as of the deuterated benzenesulphonic acid. Following assignments of bands characteristic of the sulphonic acid group are proposed: ν(OH) 2900 and 2350 cm1, νa(SO2) 1350 cm1, νs(SO2) 1160 cm1, ν(SO) 900 cm1, with very small deviations. The spectra of hydrated sulphonic acids are interpreted in terms of superposition of the spectra of the SO3 group and the H3O+ ion. The positions of the νa(SO2) and the νs(SO2) bands in sulphonic acids and their derivatives are briefly discussed. The bands due to the stretching of the single S-O bonds in aliphatic sulphites were found to appear between 690 and 760 cm1 whereas the analogous bands in the spectra of the corresponding sulphates were found at slightly higher frequencies, but were difficult to separate from the bands due to the aliphatic part of the molecule.