PREFERENTIAL SOLVATION CONTROLLED BY CLUSTERING CONDITIONS OF ACETONITRILE-WATER MIXTURES

Experimental evidence for the preferential solvation of phenol in a mixed solvent of acetonitrile and water has been obtained by mass spectrometric analysis of the clusters isolated from liquid droplets by the adiabatic expansion. The effect of temperature on the formation of phenol-hydrate clusters, (C6H5OH)(H2O)(n): n = 1, 2, 3, ..., showed that phenol molecules are solvated preferentially by acetonitrile molecules at x(w)(water mole fraction) < 0.85, the phenol-hydrate clusters were hardly observed at temperatures lower than 50 degrees C but appeared at higher temperatures. On the contrary, at x(w) greater than or equal to 0.85, hydrate formation became preferable at lower temperatures. The observed temperature effect confirmed microscopically inhomogeneous clustering of the solvent and solute molecules in the mixtures. A similar temperature effect was also observed in the emission spectra of 2-naphthol in thesame mixtures.