Thermodynamics of Ketone + Amine Mixtures. Part VIII. Molar Excess Enthalpies at 298.15 K for n-Alkanone + Aniline or + N-Methylaniline Systems

Abstract

Molar excess enthalpies, HmE, at 298.15 K and atmospheric pressure have been determined over the entire mole fraction range, using a Tian-Calvet microcalorimeter, for the systems: propanone, 2-butanone, 2-pentanone, or 2-heptanone + aniline or + N-methylaniline. The negative HmE values obtained for all of the mixtures reveal that interactions between unlike molecules are prevalent. Aniline solutions show more negative HmE values due to stronger amine-ketone interactions compared to those in N-methylaniline solutions. In addition, HmE increases with the size of the alkanone, which may be interpreted in terms of a weakening of interactions between unlike molecules. HmE varies somewhat differently in N-methylaniline solutions, probably due to the positive contribution to HmE is here more important. Molar excess internal energies at constant volume, UVmE, have been determined from the present HmE data using our previous measurements on molar excess volumes, compressibilities, and isothermal expansion coeffici...