Vapour pressures and excess functions of 1,4-dimethylpiperazine + n-heptane, or cyclohexane measurement and prediction

The vapour pressures of liquid 1,4-dimethylpiperazine + n-heptane or cyclohexane mixtures were measured by a static method between 273.15 and 363.15 K at 10 K intervals. The excess molar enthalpies, at 303.15 K were also measured. The molar excess Gibbs energies, calculated from the vapour liquid equilibrium data, and the molar excess enthalpies compared satisfactorily with group contribution (DISQUAC) predictions. The quasi-chemical contribution to the N/alkane and N/c-CH2 contact improves the agreement. The intramolecular effects (ring effect, proximity effect) would then affect the quasi-chemical parameters, keeping the dispersives ones constant.