Non-Ideal Behaviour and Solution Interactions in Binary DMSO Solutions.

The structure and dynamics of hydrogen-bonded structures are of significant importance in understanding many binary mixtures. Since self-diffusion is very sensitive to changes in the molecular weight and shape of the diffusing species, hydrogen-bonded associated structures in dimethylsulfoxide-methanol (DMSO-MeOH) and DMSO-ethanol (DMSO-EtOH) mixtures are investigated using nuclear magnetic resonance (NMR) diffusion experiments and molecular dynamics (MD) simulations over the entire composition range at 298 K. The self-diffusion coefficients of DMSO-MeOH and DMSO-EtOH mixtures decrease by up to 15% and 10%, respectively, with DMSO concentration, indicating weaker association as compared to DMSO-water mixtures. The calculated heat of mixing and radial distribution functions reveal that the intermolecular structures of DMSO-MeOH and DMSO-EtOH mixtures do not change on mixing. DMSO-alcohol hydrogen-bonded dimers are the dominant species in mixtures. Direct comparison of the simulated and experimental data afford greater insights into the structural properties of binary mixtures.