Thermodynamic study of heptane+amine mixtures. V. Excess and solvation Gibbs energies

Vapor-liquid equilibria of binary mixtures of n-heptane with 15 amines, primary n-alkyl (C3-C8), secondary (diethyl to dibutyl), branched (. iso-propyl and sec-butyl) and cyclic amines (piperidine, hexamethyleneimine, heptamethyleneimine and cyclopentylamine) have been determined by head-space gas chromatographic analysis of the vapor phase directly withdrawn from an equilibration apparatus. Excess molar Gibbs energies and activity coefficients for the systems investigated have been obtained by a least-square treatment of the equilibrium results. All mixtures exhibit positive deviations from ideality, decreasing with the amine size. The Gibbs energy of solvation for amines in heptane has been evaluated and its dependence on polar groups, chain lengthening, branching and cyclization has been discussed.