Interactions between 1-butyl-3-methylimidazolium cation with various anions and carboxylic acids: Physicochemical and spectroscopic aspects

In this work, the intermolecular interactions for binary mixtures of ionic liquids, 1-butyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium hexafluorophosphate with acetic and propionic acid were evaluated through the measurement of thermophysical properties, density (?), sound velocity (u), refractive index (nD) and surface tension (?) at T = (293.15-333. 15) K and p = 0.1 MPa. The experimental results were used to compute the thermodynamic properties of the binary mixtures, which were then fitted to the Redlich-Kister polynomial equation. The FTIR spectra of the pure components and the binary mixtures at an equimolar composition were recorded to confirm results from thermodynamic properties. The variations of the thermodynamic properties with IL mole fraction and temperature and the effect of the IL anion and alkyl length of the carboxylic acid on the thermodynamic properties have been discussed.

Automated summary

This study evaluated the intermolecular interactions between ionic liquids and acetic acid, propionic acid in binary mixtures, discussing the variations of thermodynamic properties with mole fraction and temperature, as well as the impact of IL anion and alkyl length on properties. The experimental results were used to compute thermodynamic properties and were confirmed through FTIR spectra of pure components and binary mixtures at equimolar compositions.