Physicochemical studies of molecular interactions in binary mixtures of toluene with some aliphatic nitriles at different temperatures

Densities ρ, ultrasonic speeds u and viscosities η of binary mixtures of toluene with acetonitrile (AN), propionitrile (PN) and butyronitrile (BN), including those of pure liquids are measured over the entire composition range at 298.15, 303.15 and 308.15 K and at atmospheric pressure. From these experimental data, isentropic compressibility ks, molar isentropic compressibility Ks, excess molar volume VmE, partial molar volumes V̅m,1° and V̅m,2°, excess partial molar volumes V̅m,1°E and V̅m,2°E of the components at infinite dilution are calculated. The variation of these properties with composition and temperature of the binary mixtures is discussed in terms of molecular interactions between unlike molecules of the mixtures. The values of VmE are found negative for all the mixtures at each temperature studied, indicating the presence of specific interactions between toluene and AN/PN/BN molecules. The variations of VmE values with composition indicate that the interactions in these mixtures follow the order: AN > PN > BN, i.e., the toluene-nitrile interaction decreases with increase in alkyl chain length in these nitrile molecules.