Thermodynamics Research Center / ThermoML | Journal of Chemical Thermodynamics

ABSTRACT

Densities and speeds of sound of {2-heptanone + dipropylamine (DPA), +dibutylamine (DBA), or +triethylamine (TEA)} systems have been measured at (293.15, 298.15, and 303.15) K and atmospheric pressure using a vibrating tube densimeter and sound analyzer Anton Paar model DSA-5000. The density and speed of sound values were used to calculate excess molar volumes and the excess functions at 298.15 K for the speed of sound, the thermal expansion coefficient and for the isentropic compressibility. Structural effects increase with the ketone size in mixtures with a fixed amine. Excess molar volume, excess isentropic compressibility and excess thermal expansion coefficient functions increase when DPA is replaced by DBA in systems with a given ketone as: (i) interactions between unlike molecules are more easily created in solutions containing the shorter amines; (ii) this effect predominates over that related to the disruption of the amine amine interactions. Contributions to excess molar volume from the creation of interactions between unlike molecules and from the breaking of the amine-amine interactions are both lower in absolute value for TEA systems when are compared to those of DPA solutions. The increasing positive excess molar volume values observed when DPA is replaced by TEA in solutions with propanone or 2-butanone reveal that the former contribution is less relevant, and more important for the DPA mixtures. The opposite behavior for 2-heptanone systems is attributed to the existence of structural effects when this ketone is mixed with TEA. These general trends are confirmed by the treatment of the mixtures using the PFP theory, and the internal pressure concept.