LAUSR

Abstract The densities, ρ, speeds of sound, u and refractive indices, nD of the binary mixtures of 1-butyl-3-methylimidazolium hexafluorophosphate [Bmim][PF6] with 2-methoxyethanol and 2-ethoxyethanol, including those of pure liquids, have been measured over the entire range of composition at 298.15, 303.15, 308.15, 313.15, 318.15 and 323.15 K and atmospheric pressure. The IR spectra of pure liquids and their mixtures have also been recorded at 298.15 K. From the experimental data, excess molar volumes, VmE, excess isentropic compressibility, κsE, excess speeds of sound, uE, excess molar isentropic compressibility, Ks , mE and deviations in refractive indices, ΔϕnD were calculated and fitted using the Redlich-Kister equation. The partial molar volumes, V ¯ m , 1 and V ¯ m , 2 , partial molar isentropic compressibilities, K ¯ s , m , 1 and K ¯ s , m , 2 , excess partial molar volumes, V ¯ m , 1 E and V ¯ m , 2 E , and excess partial molar isentropic compressibilities, K ¯ s , m , 1 E and K ¯ s , m , 2 E over whole composition range and partial molar volumes, V ¯ m , 1 ° and V ¯ m , 2 ° , partial molar isentropic compressibilities, K ¯ s , m , 1 ° and K ¯ s , m , 2 ° , excess partial molar volumes, V ¯ m , 1 ° E and V ¯ m , 2 ° E , and excess partial molar isentropic compressibilities, K ¯ s , m , 1 ° E and K ¯ s , m , 2 ° E of the components at infinite dilution have also been calculated. The results have been discussed in terms of intermolecular interactions prevailing in these mixtures. The VmE values for these mixtures were also calculated by using Prigogine–Flory–Patterson (PFP) theory and the results were compared with experimental findings. The results indicated that the interactions in these systems follow the order: 2-methoxyethanol > 2-ethoxyethanol.