HYDROGEN BONDING IN BINARY MIXTURES OF TETRAHYDROFURAN AND WATER: A CONCENTRATION DEPENDENT RAMAN STUDY AND AB-INITIO CALCULATIONS

Abstract: This contribution reports on the wavenumber shifts and linewidth changes observed for the Raman bands of the C-O and C-C stretching vibrations of tetrahydrofuran (THF) in a series of binary mixtures with water. Experimental results are compared with ab-initio calculations on THF and hydrogen-bonded THF-water complexes. The Raman spectroscopic analysis of vibrational relaxation processes such as vibrational dephasing is a powerful approach of investigating dynamical processes in liquids. It is possible to identify two principal mechanisms for interpreting the relaxation process. The first process involves a change in the quantum state of the relevant normal mode, while the second process is related to the phase decay of the vibrational wavefunction [1-2]. Both processes can contribute to the spectral band shape and thereby to the vibrational correlation function obtained from them. In most cases, however, vibrational band profiles are determined predominantly by vibrational dephasing. Raman spectra of neat tetrahydrofuran (THF) and its binary mixtures with water were investigated in the wavenumber intervals 1000 – 800 cm-1 and 1100 – 975 cm-1; mixtures with mole fractions of 0.1, 0.3, 0.5, 0.7 and 0.9 of the reference system THF were analyzed. Figure 1 shows the Raman spectra of neat THF and two binary mixtures with THF mole fractions of 0.5 an