Temperature dependent study of thermophysical properties of binary mixtures of imidazolium based ionic liquids with cyclic amides.

The experimental values of densities () and speeds of sound (u) of the binary mixtures of ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate [Bmim][BF4] with cyclic amides 2-Pyrrolidinone(2-PY) and N-Vinyl-2-pyrrolidone (NVP) have been used to calculate the internal pressures (i), free volumes (Vf), excess internal pressures (Ei ), excessfree volumes (Ef V), excess free energy (E G), excess enthalpy (E H) and excess entropy (E TS) covering the entirecomposition range expressed by mole fractions of ionic liquid at temperatures (298.15-323.15 K). The results have been interpreted in terms of intermolecular interactions between the component molecules in the mixture. The variations of these excess properties with composition indicate that the interactions between [Bmim][BF4] and cyclic amides in these mixtures follows the order: NVP > 2-PY. [ABSTRACT FROM AUTHOR]