Thermodynamics of mixtures containing a very strongly polar compound: V – application of the extended real associated solution model to 1-Alkanol + Secondary Amide Mixtures

The extended real associated solution (ERAS) model is applied to 1-alkanol + secondary amide mixtures. The amides considered are: N-methylformamide (NMF), N-methylacetamide (NMA) and 2-pyrrolidone (2-PY). The ERAS parameters for pure amides and for the mixtures are reported. For pure amides, our enthalpy of association is constant (−25 kJ mol−1) and is in good agreement with values obtained using different method, e.g., the optimized potentials for liquid simulations. For the mixtures, the ERAS parameters change regularly with molecular structure of the components. In general, ERAS describes quite well molar excess enthalpies and molar excess volumes. In contrast, the model cannot represent molar excess Gibbs energies. Discrepancies between experimental and calculated values are ascribed to: (a) large combinatorial entropies as in methanol + NMA, or + 2-PY systems; (b) association effects are less important than dipole–dipole interactions between amide molecules.