Thermodynamics Research Center / ThermoML | Journal of Chemical and Engineering Data

ABSTRACT

Densities,n , speeds of sound, c, and refractive indices, nD , have been measured for the systems N,N-dimethylformamide (DMF) + propanone, + 2-butanone, or + 2- pentanone in the temperature range from 293.15 to 303.15 K and at 298.15 K for the DMF + 2-heptanone mixture. Due to the high volatility of acetone, the corresponding nD measurements were developed at 293.15 K and 298.15 K. The direct experimental data were used to determine the excess molar volumes, E Vm , and the excess refractive indices, E nD , at the working temperatures. Values of the excess functions at 298.15 K, for the speed of sound, E c , the isentropic compressibility, E S e and for the excess thermal expansion coefficient, E p a , were also calculated. The investigated systems are characterized by strong amide-ketone interactions, which become weaker when the alkanone size is increased. This is supported by negative E Vm values; by the dependence on temperature and pressure of E Vm , and by positive E Pint (excess internal pressure) values. Analysis of the systems in terms of the Rao s constant indicates that there is no complex formation. In addition, negative E Vm values also reveal the existence of structural effects, which largely contribute to the excess molar enthalpy, E Hm . E Vm and E Hm values increase with the chain length of the 2-alkanone. It allows conclude that the relative E Vm variation with the ketone size is closely related to that of the interactional contribution to this excess function. Molar refraction values, Rm , show that dispersive interactions become more relevant for the systems including longer 2-alkanones