Mixtures of Diethyl Sulfoxide and Methanol: Structure and Thermodynamics

TL;DR

This study investigates the molecular structure and thermodynamic properties of diethyl sulfoxide and methanol mixtures, revealing hydrogen bonding interactions that explain their non-ideal mixing behavior.

Contribution

It provides a detailed quantum chemical analysis of DESO-MeOH mixtures, identifying hydrogen bonds and explaining their thermodynamic deviations from ideality.

Findings

Identification of a strong hydrogen bond between DESO and MeOH

Explanation of negative deviations from ideal mixing behavior

Structural and spectral evidence supporting hydrogen bonding

Abstract

Mixtures of sulfoxides with molecular solvents possess interesting physical-chemical properties and may have applications in chemical synthesis. Hereby we confirm and rationalize the previously reported excellent miscibility of diethyl sulfoxide (DESO) with methanol (MeOH). By performing a comprehensive potential energy surface investigation we identified a global minimum for each system and a significant number of local minima described at the hybrid density functional level of theory. A strong 0.18-nm-long hydrogen bond forming between the oxygen atom of DESO and the polarized hydrogen atom of MeOH was evidenced both via the structural and spectral analyses. Our results robustly explain negative deviations in the DESO-MeOH mixtures from ideal behavior and interpret the experimental observations with microscopic precision.