Thermodynamic study of heptane + amine mixtures.

A newly designed calorimetric technique and calculation procedure has been used to obtain partial molar enthalpies and excess enthalpies HE at 298.15 K for binary mixtures of heptane + primary n-alkyl (C3-C10) and + branched (iso-propyl, sec-, iso-, and tert-butyl) amines in the whole composition range. All mixtures examined showed positive HE's, which decrease with increasing amine size. From partial molar enthalpies at infinite dilution and from the known enthalpies of vaporization, the enthalpies of solvation DsolvH° have been evaluated either for amines in heptane and heptane in amines. An additive scheme of surface interactions combined with the scaled particle theory is presented to estimate and analyse different group (CH3, CH2, CH, C, NH2, O, OH, CO, CN, COO, CHO) contributions to DsolvH° as well as to its cavitational and interactional terms.