Ultrasonic and Viscometric Studies of Molecular Interactions in Binary Mixtures of Acetonitrile with Some Amides at Different Temperatures

Ultrasonic speeds (u) and viscosities (η) of binary mixtures of acetonitrile (ACN) with formamide (FA), N,N-dimethylformamide (DMF), N-methylacetamide (NMA), and N,N-dimethylacetamide (DMA), including those of pure liquids, over the entire composition range expressed by mole fraction x1 of ACN (0 ≤ x1 ≤ 1) were measured at 293.15, 298.15, 303.15, 308.15, 313.15, and 318.15 K. From the experimental data, the deviations in isentropic compressibility (Δks), in ultrasonic speed (Δu), and in viscosity (Δη), and partial molar compressibilities, ( and ) for ACN in amide and amide in ACN at infinite dilution, respectively, were calculated. The variation of these parameters with composition and temperature of the mixtures are discussed in terms of the molecular interactions in these mixtures. It was observed that the ACN–amide interaction in these mixtures follows the order: FA > NMA > DMA > DMF. The effect of the number and position of the methyl group on the amide on the molecular interactions in these mixtures is also discussed. Finally, the free energy (ΔG*), enthalpies (ΔH*), and entropies (ΔS*) of activation of viscous flow have also been obtained by using Eyring’s viscosity equation, and the dependence of ΔG*, ΔH*, and ΔS* on composition of the mixtures is also discussed.