SPECTROSCOPIC STUDY OF THE SOLVATION OF DIMETHYL-SULFOXIDE IN AQUEOUSACETONITRILE AND ACETONE SOLVENT SYSTEMS

Results of IR studies of dimethyl sulfoxide (DMSO) in water and aqueou s acetonitrile and aqueous acetone mixtures are reported. These data, along with those reported previously for a series of amides in mixed s olvents, yield information about the composition of the first solvatio n shell of the S=O or C=O chromophore in the mixed solvent. It is show n that, for each of the systems considered, the composition of the chr omophore's first solvation shell can be reproduced quantitatively by a simple mass action treatment, using only one adjustable parameter. Th is is the mean equilibrium constant, K, for the replacement of one co mponent of the mixed solvent by the other in the coordination shelf of the chromophore. It is also shown that DMSO, Like amides, can form tw o hydrogen bonds at the S=O oxygen.