Hydrogen bonding behavior of ethanol-trifluoroethanol binary mixtures and its effects on the water structure and dynamics in ternary aqueous-ethanol-trifluoroethanol solutions

Abstract

The hydrogen bonding structure and dynamics of binary ethanol (EtOH) – trifluoroethanol (TFE) mixtures and in ternary aqueous-EtOH-TFE solutions are investigated by classical molecular dynamics simulations. Presence of water reduces hydrogen bonds between EtOH and TFE due to formation of new alcohol-water hydrogen bonds. In aqueous-EtOH-TFE mixtures, the tetrahedral order of water increases as we move from water-EtOH to water-TFE solution. Our calculated translational and rotational data suggests a slower dynamic of the species in their binary as well as in the ternary mixtures. The steep rise of the orientational relaxation times for TFE indicates a stronger aggregation among TFE molecules in both binary and ternary mixtures. A faster anisotropic decay of water is also observed with increasing TFE concentrations in the ternary solutions. The hydrogen bond lifetime associated with the hydrogen of TFE (HT⋯OT/OE/OW) is multiple times higher than that of H-bonds formed by the hydrogen of EtOH (HE)/water (HW).