A vibrational spectroscopic study of water confined in benzene from ambient conditions up to high temperature and pressure

Mid-infrared and Raman spectroscopies have been used to characterise the evolution of the structure and the nature of the molecular interactions in benzene-water mixtures in the temperature range 25-305 degrees C and at constant pressure P = 160 bar. At ambient conditions, the fundamental transitions, namely, nu(1), nu(2), and nu(3), of water diluted in benzene, have been recorded. It is found from the analysis of the peak position and intensity that solitary water forms a weak pi-hydrogen bond with benzene. At constant pressure (160 bar) and constant water concentration (C-H2O = 0.2 mol l(-1)), it is shown from the evolution of the Raman profile associated with the nu(1) mode that the hydrogen bond between water and benzene is weakened upon an increase of the temperature. Furthermore, in the same temperature range and as the concentration of water increases in the mixture, the analysis of the nu(1) mode band shape shows that hydrogen-bonded dimers appear in the solution at the expense of the water-benzene complex. (C) 2000 Elsevier Science B.V. All rights reserved.