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.