VIBRATIONAL SPECTROSCOPIC STUDIES ON THE STATE OF AGGREGATION OF WATER IN CARBON-TETRACHLORIDE, IN DIOXANE AND IN THE MIXED-SOLVENTS

A detailed infrared study of the vibrational modes of water in dioxane, carbon tetrachloride and a mixed solvent as a function of concentration is reported. H2O/D2O mixtures have been used in order to isolate the uncoupled v(OH) and v(OD) modes. The data have been interpreted in terms of the state of aggregation of water molecules in a hydrophobic solvent and in a solvent to which hydrogen bonding can occur. It is shown that at very low concentrations (x(H2O) = 5x10(4)) water exists in the monomeric form and can rotate rather freely. However, water is strongly self aggregated in a hydrophobic organic solvent for concentrations greater than x(H2O) = 5x10(-3) (ie if there are more than 5 water molecules in a 1000 solvent molecule 'bath'). Evidence of distinct (dioxane)(m)(water)(n) complexes is found in dioxane solution and in the mixed solvent. However, as the water concentration is increased it is clear that a water/solvent 'network' is formed. The aggregation processes involving water depend critically, however, on the hydrophobicity of the solvent mixture.