Study of tetraalkylammonium salts in acetonitrile solutions: Transport properties, density, thermal expansion and phase transitions

The electrical conductivity of binary solutions of tetraethylammonium trifluoromethanesulfonate ([TEA] [OTf]), tetraethylammonium tetrafluoroborate ([TEA][BF4]) and spiro-(1,1')-bipyrrolidinium tetrafluorob-orate ([SBP][BF4]) in acetonitrile was measured at atmospheric pressure in the temperature range of 293.15-348.15 K for different salt mole fractions. The highest electrical conductivities of the acetonitrile solutions of [TEA][BF4], [SBP][BF4] and [TEA][OTf] were 96 +/- 7, 94.5 +/- 0.5 and 71.6 +/- 0.5 mS center dot cm-1, respec-tively, at 348.15 K. The activation energy of the conductivity for nonassociating electrolytes was calcu-lated using the Arrhenius equation, and the activation energy of the ionic conductivity of glass -forming liquids was calculated using the Vogel-Fulcher-Tamman equation. The cation and anion diffusion coefficients in the [TEA][OTf], [TEA][BF4] and [SBP][BF4] solutions in acetonitrile were determined by the robust pulsed-gradient stimulated echo sequence technique. Experimental density data were used to cal-culate the isobaric thermal expansion coefficients in the temperature range of 293.15-348.15 K. The ther-mophysical properties (the temperatures and heats of the phase transitions and the melting temperatures) of the pure salts and their binary solutions in acetonitrile were determined by differential scanning calorimetry. (c) 2022 Elsevier B.V. All rights reserved.

Automated summary

This study measured the electrical conductivity of three ammonium salts in acetonitrile with different salt mole fractions. The study calculated the conductivity and diffusion coefficients of the salts, as well as the thermal expansion coefficients and thermophysical properties at different temperatures.