Thermodynamics Research Center / ThermoML | Thermochimica Acta

ABSTRACT

Densities, , and speeds of sound, u, of 2-butanone +dipropylamine, +dibutylamine or +triethylamine systems have been measured at (293.15, 298.15 and 303.15 K) and atmospheric pressure using a vibrating-tube densimeter and sound analyser Anton Paar model DSA-5000. The and u values were used to calculate excess molar volumes, VE, at the three temperatures, and the excess functions at 298.15K for the speed of sound, uE, the thermal expansion coefficient, ^2EP , and for the isentropic compressibility, E S . VE, E S and ^2EP are positive magnitudes. When replacing dipropylamine by dibutylamine or triethylamine in the studied mixtures, the excess functions increase. This may be ascribed to the interactions between unlike molecules are more important in the former solutions. From the comparison with similar data obtained for propanone or 2-butanone +aniline, +N-methylaniline, or +pyridine systems, it is concluded that interactions between unlike molecules are stronger in mixtures containing aromatic amines. The replacement of 2-butanone by propanone in mixtures with dipropyl, dibutyl or triethylamine leads to increased VE values, which may be explained assuming that the higher positive contribution to VE from the disruption of the propanone propanone interactions overcompensates the larger negative contribution related to stronger interactions between unlike molecules. Calculations in the framework of the Flory model support this conclusion. Free volume effects are present in solutions with dipropyl or dibutylamine as the VE curves are shifted towards higher mole fractions of 2-butanone.