The high-frequency dielectric spectroscopy of the aqueous solutions of tetrabutylammonium carboxylates

The studies of complex permittivity and low-frequency conductivity of aqueous tetrabutylammonium formate and propionate solutions were carried out in the frequency region of maximum dispersion of dielectric permittivity of water. The measurements were made over a wide range of concentrations, in the temperature interval 288–308 K. The dielectric relaxation time (τ  ) and activation enthalpy (ΔHε++) were calculated. There is an increase in these parameters in aqueous tetrabutylammonium formate and propionate solutions in comparison with pure water. The concentration dependences of τ   and ΔHε++ relate to the structure-forming effect of tetrabutylammonium and propionate ions on water through hydrogen bonding. The stabilization of the water structure is determined by the hydrophobic hydration of these ions. The hydrophobic hydration increases in going from tetrabutylammonium formate to tetrabutylammonium propionate aqueous solutions.