Reactions in Mixed Non-aqueous Solutions containing Sulphur Dioxide. Part 7.' A Raman Spectroscopic Study of Adduct Formation between Sulphur Dioxide and Dimethyl Sulphoxide

Details are given of the v ( S O ) ~ ~ ~ ~ stretching (dmso = dimethyl sulphoxide), v,(SO,), v,(SO,), and v,(SO,) regions of the Raman spectra of SO,-dmso mixtures at 293 K and sub-ambient temperatures. Analysis of the v( SO)dmso region, which contains at least seven component bands, provides evidence of several component species. Bands at 1 067,l 057, and 1 044 cm-l are due to monomers and associates of dmso, and a band whose frequency varies between 1 029 and 1 025 cm-' is due to a methyl-rocking mode of dmso. Bands at 1 01 3 , l 006, and 997 cm-l are attributed to the adducts S02.2dmso, SO,-dmso, and 2SO,-dmso respectively. A n example of the use of band fitting to a difference spectrum supports these assignments.