AN INFRARED SPECTROSCOPIC STUDY OF THE PREFERENTIAL SOLVATION IN WATER ACETONITRILE MIXTURES

Mixtures of water and acetonitrile in the full concentration range have been studied by infrared spectroscopy. OD and CN stretching vibrations of HDO and CD3CN molecules have been used as probes of the structural environments. Acetonitrile molecules which are unaffected by water molecules are found for a broad concentration range (0.1 less-than-or-equal-to x(H2O) less-than-or-equal-to 0.8), showing that a preferential solvation occurs. The strong tendency for self-association of water molecules is evident from the occurrence of a broad OD stretching band. Chains of water molecules linked by hydrogen bonds are suggested to be formed rather than spherical clusters.