Thermodynamics Research Center / ThermoML | Journal of Chemical Thermodynamics

ABSTRACT

Excess molar volumes at 298.15 K were determined by means of a vibrating tube densimeter for binary mixtures of heptane + primary n-alkyl (C3 to C10) and branched amines (iso-propyl-, iso-, sec-, and tert-butyl-, iso-, tert-pentyl-, and pentan-3-amine) in the whole composition range. The apparent molar volumes of solid dodecyl- and tetradecylamine in heptane dilute solution were also determined. The excess molar volume values were found positive for mixtures involving C3 to C8 linear amines, with excess molar volume decreasing with chain lengthening. Heptane + nonyl and decylamine showed s-shaped, markedly asymmetric, curves. Mixtures with branched C3 to C5 amines displayed positive excess molar volume larger than those observed in the mixtures of the corresponding linear isomers. Partial molar volumes at infinite dilution in heptane were evaluated for the examined amines and compared with those of alkanes and alkanols taken from the literature. An additivity scheme, based on the intrinsic volume approach, was applied to estimate group (CH3, CH2, CH, C, NH2, and OH) contributions to partial molar volumes at infinite dilution. The effect of branching on partial molar volumes at infinite dilution and the limiting slope of the apparent excess molar volumes were evaluated and discussed in terms of solute-solvent and solute-solute interactions.