ABSTRACT
Molecular dynamics simulations have been performed to investigate the thermodynamic and structural properties as well as the self diffusion coefficients and hydrogen bonding in aqueous (binary) mixtures containing the aprotic solvents acetone, acetonitrile, dimethyl sulfoxide (DMSO) and dimethylformamide (DMF). The self diffusion coefficients of both components in the mixtures were calculated and compared. The results show a non-linear dependence with composition. In each case, this property also reveal a peculiar minimum at mole fraction in the range xAS=0.35 −0.40 (AS=aprotic solvent). The diffusion coefficients of water-acetone are found to be anomalous and, the diffusion coefficients of water show a different behavior in this mixture compared with that in the other two mixtures. The intermolecular structure of each mixture was investigated and a number of interesting structural effects have been noted. In the case of acetone and acetonitrile water mixtures, there is a loss of tetrahedral water coordination in the systems In the case of DMSO and DMF water mixtures, the analysis of several site – site pair distribution functions reveals that the average tetrahedral coordination of water is preserved for mole fractions of DMSO or DMF, up to 0.4. Finally, the hydrogen bonding statistics are obtained and compared with available experimental results.
