ENTHALPIES OF MIXING OF WATER WITH N,N-DISUBSTITUTED AMIDES OF ALIPHATIC CARBOXYLIC-ACIDS

The enthalpies of mixing of N,N-dialkylpropionamides with water were m easured at 298.15 K. A comparative analysis of enthalpy effects (H-E) of mixing of water with N,N-disubstituted amides of formic, acetic, an d propionic acids was performed. It was established that the H-E value s depend on the length of the N,N-alkyl substituents and the size of a cidic radicals. The size of the nonpolar group and the electron-donor ability of amide molecules primarily affect the enthalpy of mixing. Th e relative electron-donor abilities of the amides were estimated by th e calorimetric method. The results obtained were discussed by invoking thermochemical data for aqueous solutions of hexamethylphosphoric tri amide.