Thermodynamics of mixtures containing aromatic nitriles

Abstract

The coexistence curves of liquid-liquid equilibrium (LLE) for the mixtures: phenylacetonitrile + heptane, + octane, + nonane, + cyclooctane, or + 2,2,4-trimethylpentane and for 3-phenylpropionitrile + heptane, or + octane are reported. Aromatic nitrile + alkane, + aromatic hydrocarbon or + 1 alkanol systems are investigated using a set of thermophysical properties: phase equilibria (solid-liquid, SLE, vapour-liquid, VLE and LLE), excess molar functions, enthalpies (HE m), isochoric internal energies (UE Vm), isobaric heat capacities (CEpm) and volumes (VEm), and the Kirkwood’s correlation factor. Due to proximity effects between thephenyl and the CN groups, dipolar interactions between molecules of aromatic nitriles are stronger thanthose between molecules of isomeric linear nitriles. Dipolar interactions become weaker in the order: 3-phenylpropionitrile > phenylacetonitrile > benzonitrile. Benzonitrile + aromatic hydrocarbon mixtures are characterized by dispersive interactions and structural effects. The latter are more important in systems with phenylacetonitrile. Structural effects are also present in benzonitrile + n-alkane, or + 1-alkanol + mixtures. The systems mentioned above have been studied using DISQUAC. Interaction parameters for contacts where the CN group in aromatic nitriles participates are given. DISQUAC describes correctly any type of phase equilibria, CEpm of benzonitrile + hydrocarbon mixtures and HEm of benzonitrile + cyclohexane, or 1-alkanol systems. Large differences encountered between theoretical HEm values and experimental data for some solutions are discussed. 1-Alkanol + benzonitrile mixtures are also investigated by means of the ERAS model. ERAS represents well HEm of these systems. The Vem curves of solutions with longer 1-alkanols are more poorly described, which has been explained in terms of the existence of structural effects.