Thermodynamic properties of binary mixtures of n-butylammonium-based ionic liquids with ethanol at T = (293.15–313.15) K

Abstract

In this study, density, speed of sound and viscosity of binary mixtures of ionic liquids + ethanol have been measured as a function of composition at T = (293.15–313.15) K and atmospheric pressure. The ionic liquids studied were: {n-butylammonium acetate (N4Ace), n-butylammonium propanoate (N4Pro), n-butylammonium hexanoate (N4Hex), and n-butylammonium decanoate (N4Dec)}. Excess molar volume, $$V_{\text{m}}^{\rm{E}}$$ , deviation in isentropic compressibility, $$\Delta \kappa_{\text{S}}$$ , deviation in viscosity, $$\Delta \eta$$ , and excess Gibbs energy of activation of viscous flow, $$\Delta G^{ * \rm{E}}$$ , were obtained from experimental results and correlated with the Redlich–Kister polynomial equation. Ionic liquids were synthesized and characterized using 1H-NMR, 13C-NMR and FTIR spectroscopy techniques. For all systems studied, the values of $$V_{\text{m}}^{\rm E}$$ , $$\Delta \kappa_{\text{S}}$$ and $$\Delta \eta$$ were negative over the entire composition range, whereas $$\Delta G^{ * \rm{E}}$$ values were positive over the entire composition range. The results obtained were discussed in terms of structural effects and intermolecular interactions between like and unlike molecules.