Thermodynamics Research Center / ThermoML | Fluid Phase Equilibria

ABSTRACT

Excess molar enthalpies, HmE, over the whole composition range have been determined for the liquid mixtures N,N-dimethylformamide (DMF) or N,N-dimethylacetamide (DMA) + butan-1-amine (BA), or + hexan-1-amine (HxA), or + N-propylpropan-1-amine (DPA), or N-butylbutan-1-amine (DBA) at 298.15 K and at 0.1 MPa using a BT2.15 calorimeter from Setaram adapted to work in dynamic mode at constant temperature and pressure. All the HmE values are positive, indicating that interactions between like molecules are predominant. The replacement of DMF by DMA in systems with a given amine leads to lower HmE results, which have been ascribed to stronger amide-amide interactions in DMF mixtures. The replacement of HxA by DPA in systems with a given amide leads to slightly higher HmE values, as interactions between unlike molecules are weaker for the latter. Structural effects in the investigated solutions are also present, since the corresponding excess molar volumes (VmE), previously determined, are negative or slightly positive. The systems have been characterized in terms of the ERAS model reporting the interaction parameters. The model correctly describes both HmE and VmE. The application of the model suggests that, in the systems under study, solvation effects are of minor importance and that physical interactions are dominant.