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 ν(SO)dmso stretching (dmso = dimethyl sulphoxide), ν1(SO2), ν3(SO2), and ν2(SO2) regions of the Raman spectra of SO2–dmso mixtures at 293 K and sub-ambient temperatures. Analysis of the ν(SO)dmso region, which contains at least seven component bands, provides evidence of several component species. Bands at 1 067, 1 057, and 1 044 cm–1 are due to monomers and associates of dmso, and a band whose frequency varies between 1 029 and 1 025 cm–1 is due to a methyl-rocking mode of dmso. Bands at 1 013, 1 006, and 997 cm–1 are attributed to the adducts SO2·2dmso, SO2·dmso, and 2SO2·dmso respectively. An example of the use of band fitting to a difference spectrum supports these assignments.