Experimental solid + liquid equilibria and excess molar volumes of alkanol + hexylamine mixtures: Analysis in terms of the ERAS, DISQUAC and Mod. UNIFAC models

Abstract

Solid+liquid phase diagrams (SLE) have been determined for octan-1-ol, or nonal-1-ol, or decan-1-ol, or undecan-1-ol+hexylamine mixtures. Solid addition compounds form with the empirical formulae: (C 8H 17OH·C 6H 15N), (C 9H 19OH·C 6H 15N), (C 10H 21OH·C 6H 15N) and (C 11H 23OH·C 6H 15N). All these compounds are congruently melting compounds. Compound formation is attributed to a strong OH⋯O and NH⋯N hydrogen bonds. Excess molar volumes, V m E have been determined for an alcohol (octan-1-ol, or nonal-1-ol, or decan-1-ol, or undecan-1-ol) + hexylamine at 298.15 K and atmospheric pressure. The systems exhibit very large negative molar excess volumes, V m E and excess molar enthalpies, H m E. Our experimental data of V m E and the literature data of H m E were treated in terms of ERAS model, DISQUAC and Mod. UNIFAC. DISQUAC is the only model that can be used to accurately represent excess molar enthalpies. Mod. UNIFAC overestimates the self-association of the alcohol in the solutions under study. Currently, the ERAS model can be used to examine V m E of these solutions but the same ERAS parameters overestimate the strong interactions between unlike molecules.