Densities, ultrasonic speeds, refractive indices, excess and partial molar properties of binary mixtures of imidazolium based ionic liquid with pyrrolidin-2-one at temperatures from 298.15 L to 323.15 K

•Study reports new density, speed of sound and refractive index data of [Bmim][NTf2] + pyrrolidin-2-one binary mixtures.•Provides estimation of excess properties of [Bmim][NTf2] + pyrrolidin-2-one binary mixtures.•Provides information on nature of interactions in these mixtures.•The applicability of PFP theory in predicting the excess molar volumes of these mixtures was checked.

The densities, ρ, speeds of sound, u and refractive indices, nD of binary mixtures of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [Bmim][NTf2] and pyrrolidin-2-one, including those of pure liquids, over the entire composition range were measured at temperatures (298.15, 303.15, 308.15, 313.15, 318.15 and 323.15) K and atmospheric pressure. Using the experimental results, the excess molar volume, VmE, excess isentropic compressibility, κsE, excess molar isentropic compressibility, Ks,mE, excess speed of sound, uEuE, deviations in refractive index, ΔϕnDΔϕnD, deviations in molar refraction, ΔRMΔRM have been calculated. The partial molar volume and compressibility, excess partial molar volume and compressibility over the whole composition range; and the partial molar volume and compressibility, and excess partial molar volume and compressibility, of the components at infinite dilution have also been calculated. The excess properties were correlated by the Redlich–Kister polynomial equations. The variations of these parameters with composition and temperature are 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 are compared with experimental findings.

Graphical abstractExcess isentropic compressibilities, κsE as function of mole fraction, x1 of [Bmim][NTf2] for [Bmim][NTf2] and pyrrolidin-2-one binary mixtures.Figure optionsDownload full-size imageDownload as PowerPoint slide