Thermodynamics of Mixtures Containing a Strongly Polar Compound. 8. Liquid−Liquid Equilibria for N,N-Dialkylamide + Selected N-Alkanes

Abstract

The coexistence curves of the liquid−liquid equilibria (LLE) for systems of dimethylformamide (DMF) with hexane, heptane, octane, or nonane and of dimethylacetamide (DMA) with heptane have been determined visually. All the curves show an upper critical solution temperature (UCST) and have a rather horizontal top. The measured LLE curves for DMF mixtures show that their symmetry depends on the size of the alkane. For a given alkane, the UCST is higher for systems with DMF. This reveals that dipole−dipole interactions between amide molecules are stronger in such solutions. The DISQUAC model represents fairly well the LLE curves.