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

Abstract

The 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 ≤ x TBA ≤ 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 χ (ν) 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.

Aqueous solvation of amphiphilic solutes: concentration and temperature dependent study of the ultrafast polarisability relaxation dynamics

“…The Raman spectra of TBA solutions (which contain data analogous to the Im [D 0 (o)]) have been reported before by Tominaga et al 72 and Sassi et al, 16 although their data were collected at relatively high concentrations (>2.3 M 72 and >9.5 M 16 ). Tominaga et al 72 showed that the spectra of TBA-water solutions could be decomposed into linear combinations of water and neat TBA spectra in the frequency range 80-400 cm À1 .…”

“…Tominaga et al 72 showed that the spectra of TBA-water solutions could be decomposed into linear combinations of water and neat TBA spectra in the frequency range 80-400 cm À1 . Sassi et al 16 reported that the spectral evolution observed by varying the concentration from pure TBA down to 9.5 M was similar to the effect produced by lowering the temperature of neat TBA. The Im [D 0 (o)] obtained from OHD-OKE measurements are shown in Fig.…”

“…[1][2][3][4][5][6][7] A large number of studies concerned aqueous solutions of TMAO (trimethylamine N-oxide) and TBA (t-butyl alcohol). [8][9][10][11][12][13][14][15][16][17][18][19] The hydrophobic part of both consists of three methyl groups, while their hydrophilic parts differ, with that of TMAO consisting of a polar N + O À group and that of TBA a hydroxyl group (Fig. 1).…”

Hydrophobic Hydration in Water–tert-Butyl Alcohol Solutions by Extended Depolarized Light Scattering

“…The asymmetric band at ca. 50 cm −1 is typical of many hydrogen-bonding liquids, 60 including aliphatic alcohols 61 , 62 and is generally ascribed to librational motions of the solute molecules. 61 Here, the comparison with the spectrum of pure TBA (Figure 7) confirms this assignment.…”

Recent advances in linear and nonlinear Raman spectroscopy. Part IV

“…Dong et al [250] used spatially resolved Raman scattering together with in situ microscopy to study mixed Na 2 SO 4 /MgSO 4 aerosol particles with molar ratios of 1 : 1 and 2 : 1 deposited on a quartz substrate to gain a better understanding of their evaporation processes. Sassi et al [251] used low-frequency Raman scattering to study the collective motions in liquid tert-butanol. Vibrational and relaxation phenomena of this H-bonding system were assessed in pure liquid phase at different temperatures and in solution with 2,2-dimethylbutane and water as a function of composition.…”