Thermodynamics of (ketone + amine) mixtures. Part VI. Volumetric and speed of sound data at (293.15, 298.15, and 303.15) K for (2-heptanone + dipropylamine, +dibutylamine, or +triethylamine) systems

Densities, ρ, and speeds of sound, u, 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 ρ and u   values were used to calculate excess molar volumes, VmE, and the excess functions at 298.15 K for the speed of sound, uE, the thermal expansion coefficient, αPE, and for the isentropic compressibility, κSE. Structural effects increase with the ketone size in mixtures with a fixed amine. VmE, κSE, and αPE 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 VmE 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 VmE 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.

► VmE, uEuE, κSE, and αpE data for (2-heptanone + DPA, +DBA, or +TEA) systems have been determined.
► Structural effects increase with the ketone size in systems with a given amine.
► They are dominant for (2-heptanone + DPA, or +TEA) solutions.
► Interactions between unlike molecules are more easily created in solutions with the shorter amines.
► The application of the PFP theory and the internal pressure concept confirm these trends.