Influence of temperature on thermodynamics of protic ionic liquid 2-hydroxy diethylammonium lactate (2-HDEAL) + short hydroxylic solvents

Abstract

In this work, we synthesized the protic ionic liquid 2-hydroxy diethylammonium lactate (2-HDEAL), the volumetric and acoustic behavior into different hydroxilic media (water, methanol and ethanol) at the range of temperature 288.15–323.15K and atmospheric pressure being studied. The corresponding apparent molar volume and apparent molar isentropic compressibility values have been evaluated from the experimental data and fitted to a temperature dependent Redlich–Mayer equation. Derived properties such as isobaric expansibility isothermal coefficient of pressure excess molar enthalpy and other acoustical parameters were computed due to their importance in the study of specific molecular interactions into this environment. The new experimental data were used to test the prediction capability of different models (Mchaweh–Nasrifar–Moshfeghian (MNM) model, the modified Heller temperature dependent equation (MHE) and the Collision Factor Theory (CFT)). The obtained results indicate that ionic liquid interactions in water are weaker than in the studied alcoholic solutions, in accordance with previous results. The excess molar volumes were negative throughout the composition range for all mixtures at any temperature condition. The observed inverse dependence on temperature for aqueous or alcoholic mixtures, points out the special trend of packing of this protic ionic liquid into hydroxilic solvents and its strong dependence on steric hindrance of aliphatic residues into anions and cations.