Concentration‐Dependent Hydrogen‐Bonding Effects on the Dimethyl Sulfoxide Vibrational Structure in the Presence of Water, Methanol, and Ethanol

Abstract

The effects of hydrogen bonding between dimethyl sulfoxide (DMSO) and the co-solvents water, methanol, and ethanol on the symmetric and antisymmetric CSC stretching vibrations of DMSO are investigated by means of Raman spectroscopy. The Raman spectra are recorded as a function of co-solvent concentration and reflect changes in structure and polarizability as well as hydrogen-bond donor and acceptor ability. In all cases studied a nonideal mixing behavior is observed. The spectra of the DMSO/water system show blue-shifted CSC stretching modes. The antisymmetric frequencies are always further blue-shifted than the symmetric stretching ones. The DMSO/methanol system also features blue-shifted CSC stretching frequencies but at high mole fractions a pronounced red shifting is observed. In the binary DMSO/ethanol system, the co-solvent also gives rise to blue shifts of the CSC stretching frequencies but restricted to mole fractions between x=0.38 and 0.45. The different magnitudes and occurrences of both blue- and red-shifted spectral lines are comprehensively and critically discussed with respect to the existing literature concerning wavenumbers and Raman intensities in both absolute and normalized values. In particular, the normalized Raman intensities show a higher sensitivity for the nonideal mixing behavior because they are independent of the mole fraction.

Origin of 5‐Hydroxymethylfurfural Stability in Water/Dimethyl Sulfoxide Mixtures

“…The low frequency part of the OÀH stretching band at~3300 cm À1 is caused by the vibrations of OÀH groups with stronger HBs than those that have their OÀH stretching band in the vicinity of~3400 cm À1 . [24] Thus, we observe a blueshift in the CÀSÀC symmetric and asymmetric vibrations and a redshift in the S=O stretching vibration. Based on our calculations, the HMF OÀH stretching vibration appears at lower wavenumbers (~3290-3350 cm À1 ) if it is an HB donor to a DMSO molecule than to a water O atom (~3470-3520 cm À1 ), which indicates stronger binding with DMSO.…”

The local environment of the molecules in water–DMSO mixtures, as seen from computer simulations and Voronoi polyhedra analysis

“…In fact, there is a convergence in the literature that in the DMSO mole percentage range of 30-40 % the water-DMSO interactions due to hydrogen bonds are at maximum. 18 Indeed, DMSO:water complexes of the stoichiometry of 2:1 at high DMSO mole fraction, 24,26,30,32 as well as of 1:2, 6,8,24,[26][27][28] 2:3, 27 and 1:3 33 at low DMSO content were proposed in the literature, although the existence of the latter has also been questioned. 27 However, such complexes were rather scarcely observed directly, e.g., through a detailed multiparticle spatial distribution analysis, 27 instead, their existence was merely hypothesized in explaining anomalous dynamical and thermodynamic properties of the mixture and other experimental data, or concluded on the basis of indirect evidences, such as radial distribution functions.…”

Recent Advances in the Characterization of Gaseous and Liquid Fuels by Vibrational Spectroscopy

“…A prominent example of such non-ideal mixing behavior is the solution of one part dimethyl sulfoxide (DMSO) and two parts of water. While the pure substance melting points are +18 °C and 0 °C, respectively, the mixture melts at −70 °C [8,9]. Therefore, it is important to characterize a mixture, in particular when it is a multi-component system like most commercial fuels are.…”