Characterization of 1-alkanol + strongly polar compound mixtures from thermophysical data and the application of the Kirkwood-Buff integrals and Kirkwood-Fröhlich formalisms

Abstract

Mixtures formed by 1-alkanol and one strongly polar compound (nitromethane (NM), ethanenitrile (EtN), dimethyl sulfoxide (DMSO), sulfolane (SULF), nitrobenzene (NTBz) or benzonitrile (BzCN)) have been investigated on the basis of a set of thermophysical data, which includes: excess molar functions (enthalpies, $H_{\text{m}}^{\text{E}}$, Gibbs energies, $G_{\text{m}}^{\text{E}}$, entropies, $T S_{\text{m}}^{\text{E}}$, isobaric heat capacities, $C_{p \text{m}}^{\text{E}}$, volumes, $V_{\text{m}}^{\text{E}}$); liquid-liquid equilibria (LLE), excess permittivities and deviations from the linearity of dynamic viscosities. In addition, calculations have been conducted to determine the Kirkwood-Buff integrals and the Kirkwood correlations factors, $g_{\text{K}}$, of the investigated mixtures. In the former case, DISQUAC has been employed for modeling the needed vapour-liquid equilibria data. Many systems under consideration are characterized by dipolar interactions between like molecules and have positive values of $H_{\text{m}}^{\text{E}}$, $C_{p \text{m}}^{\text{E}}$ and $T S_{\text{m}}^{\text{E}}$. On the other hand, alkanol-solvent interactions, for mixtures with a fixed 1-alkanol, become weakened in the sequence: DMSO $\approx$ SULF > EtN > NM > BzCN > NTBz. In systems with a given solvent, such interactions become also weaker when the chain length of the 1-alkanol is increased. Interestingly, the considered mixtures also show strong structural effects. Results on Kirkwood-Buff integrals reveal that nitriles are more preferred than nitroalkanes around a central alcohol molecule. Calculations on $g_{\text{K}}$ show that, in terms of the mixture polarization, the systems are rather unstructured, and that this trend becomes more important when the 1-alkanol size increases in solutions with a given solvent.