Microwave dielectric properties of aqueous trifluoroacetic acid solutions

Microwave dielectric properties of aqueous trifluoroacetic acid solutions are determined in the region of maximal permittivity dispersion of water (10–26 GHz) at temperatures of 288, 298, and 308 K. Static dielectric permittivities and dielectric relaxation times and activation parameters are calculated. The molecular-kinetic stabilization of water is observed in the solutions under study at a lowered temperature (288 K). Increases in degree of connectivity and in degree of structuring of the H-bond network of water in aqueous trifluoroacetic acid solutions are inferred from an analysis of temperature-induced changes of the relaxation effects, which are dictated by the hydrophobic hydration of trifluoroacetate ion, in turn associated with the effect of its low-polarity CF3 group.