Thermodynamic and spectroscopic study of molecular interactions in the binary liquid mixtures of N-methyl-2-pyrrolidone and some substituted benzenes at different temperatures

The densities and viscosities for pure liquids N-methyl-2-pyrrolidone (NMP), aniline (AB), bromobenzene (BB), chlorobenzene (CB) and their binary mixtures containing NMP as a common component have been measured at 303.15, 308.15, 313.15 and 318.15 K as a function of composition of NMP. From these results, excess molar volumes, excess Gibbs free energy of activation of viscous flow and deviations in viscosity are computed. Excess properties are fitted to a Redlich-Kister type equation and the corresponding standard deviations are calculated. The experimental data of viscosity is used to test the applicability of empirical relations of Grunberg-Nissan, Katti-Chaudhri, Heric-Brewer and Hind et al. for the systems studied. The excess molar volumes are found to be negative whereas the deviations in viscosity and excess Gibbs free energy of activation of viscous flow values are found to be positive for all the mixtures, over the entire composition range. Partial molar volumes and apparent molar volumes at infinite dilution have been calculated. The variation of these properties with composition of NMP and temperature is discussed in terms of molecular interactions between component molecules. The strength of interaction of AB, BB, CB with NMP is found to obey the order AB > CB > BB. The IR, spectral studies of these binary mixtures also suggest specific interaction between the unlike molecules of the components and supported thermodynamic findings. (C) 2012 Elsevier B.V. All rights reserved.