The Influence of Trifluoromethyl Groups on the Miscibility of Fluorinated Alcohols with Water: A Molecular Dynamics Simulation Study of 1,1,1-Trifluoropropan-2-ol in Aqueous Solution

Abstract

1,1,1-Trifluoro-propan-2-ol (TFIP) alcohol has been used to study the influence of trifluoromethyl groups (CF3) on the physicochemical properties of fluorinated organic molecules. TFIP contains both a CF3 and a methyl (CH3) group. An atomistic study of TFIP thus can provide insight into the behavior of the two groups in water. First, an all-atom model of TFIP was parametrized to reproduce the experimental density, pressure, and enthalpy of vaporization of the pure racemic liquid at 298 K. Mixtures of TFIP with water were then simulated at 298 K, and the structural, thermodynamic, and kinetic properties obtained were compared with the available experimental data. The structure of the hydratation shell of the CF3 group was found to be concentration-dependent. At concentrations at which TFIP and water are miscible, the organization of water around the CF3 groups was similar to that found around the CH3 groups. At concentrations at which TFIP and water are not miscible, the water around the CF3 group was highly disordered. The structure of the water cage around the CH3 groups was found to be similar for all of the water concentrations. This difference in organization of the hydratation shell around the CF3 and CH3 groups may play a key role in determining the unusual miscibility behavior of TFIP as compared with other fluorinated compounds such as 2,2,2-trifluoroethanol and 1,1,1,3,3,3-hexafluoropropan-2-ol.