Thermodynamics of amide+amine mixtures. 5. Excess molar enthalpies of N,N-dimethylformamide or N,N-dimethylacetamide+N-propylpropan-1-amine, +N-butylbutan-1-amine, +butan-1-amine, or +hexan-1-amine systems. ERAS results

Abstract

Excess molar enthalpies, $H_{\text{m}}^{\text{E}}$, 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 $H_{\text{m}}^{\text{E}}$ 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 $H_{\text{m}}^{\text{E}}$ 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 $H_{\text{m}}^{\text{E}}$ 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 ($V_{\text{m}}^{\text{E}}$), 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 $H_{\text{m}}^{\text{E}}$ and $V_{\text{m}}^{\text{E}}$. The application of the model suggests that, in the systems under study, solvation effects are of minor importance and that physical interactions are dominant.