Liquid–liquid equilibria for acetophenone + n-alkane mixtures and characterization of acetophenone systems using DISQUAC

Abstract

Liquid–liquid equilibrium (LLE) temperatures have been determined for acetophenone+CH3(CH2)uCH3 (u=8,10,12,14) mixtures by means of the opalescence method using a laser scattering technique. All the solutions show an upper critical solution temperature (UCST), which increases almost linearly with u. Acetophenone+benzene, or +alkane, or +1-alkanol mixtures have been treated by means of the DISQUAC model. The corresponding dispersive and quasi-chemical interaction parameters for the contacts CO/aromatic; CO/aliphatic; CO/c-CH2 and CO/hydroxyl are reported. The model correctly describes LLE diagrams and excess molar enthalpies, HmE, of the investigated solutions, over a wide range of temperature using the same set of interaction parameters. Mixtures with alkanes are mainly characterized by dipolar interactions. From the analysis of molar excess functions: HmE, volumes, VmE, and internal energies at constant volume, UVmE, and on LLE for such systems, it is shown that interactions between acetophenone molecules are stronger than those between 2-hexanone or 2-octanone molecules and that they are similar to acetone–acetone interactions. Thus, the phenyl ring in acetophenone leads to strengthened interactions between alkanone molecules. Dipolar interactions are also important in mixtures containing 1-alkanols, and become more relevant in solutions with longer 1-alkanols. The enthalpy of the alcohol–acetophenone interactions, ΔHOH–CO, were determined. This magnitude increases with the alkanol size and remains practically constant from 1-butanol.