A study of collective motions in liquid tert‐butanol from low‐wavenumber Raman scattering

Abstract

AbstractThe collective properties of liquid tert‐butyl alcohol (TBA) were analysed by low‐wavenumber Raman (LWR) scattering spectroscopy. Vibrational and relaxation phenomena of this H‐bonding system were assessed in pure liquid phase at different temperatures in the 15–70 °C range, and in solution with 2,2′‐dimethyl butane (2,2′‐DMB) and water as a function of composition in the 0.7⩽xTBA⩽0.9 range at constant temperature (T = 25 °C). The LWR spectrum of pure TBA (below 150 cm−1) was expressed by the dynamical (or Raman) susceptibility ???? and reproduced by curve fitting using three functional forms. The high‐wavenumber band, whose intensity is poorly dependent on the temperature, was assigned to the ultrafast librational mode; the remaining components with an intensity that increased with temperature were attributed to relaxation dynamics in the range of picosecond (‘slow’ 3 ps) and sub‐picosecond (‘fast’, 0.4 ps) timescales. Adding 2,2′‐DMB to TBA had no significant effect on the intermolecular interactions in alcohol‐rich solutions, with almost unchanged LWR scattering features. On the other hand, water added to TBA determined an increase in interactions, similar to the effect of a temperature decrease in pure liquid alcohol; this was clearly depicted by the LWR profiles. Moreover, through the analysis of the OH stretching bands of water in solution, the confinement of aqueous pools in the hydrophilic spaces of alcohol‐rich solutions was confirmed. Copyright © 2009 John Wiley & Sons, Ltd.