The vapour pressure of liquid n-heptane + N,N,N’,N’-tetramethylalkanediamine, (CH3)(2) N-(CH2)(u-)N(CH3)(2) (u = 1,2), mixtures were measured by a static method in the 303.15-343.15 K range at 10 K intervals. The excess molar enthalpies were also measured at 303.15 K. The molar excess Gibbs energies, calculated from the vapour-liquid equilibrium data and the molar excess enthalpies compare satisfactorily with group contribution (DISQUAC) predictions. The proximity effect of N-atoms produces a regular decrease of the interaction parameters.