Enthalpy Characteristics and State of N,N-Disubstituted Amides of Formic and Acetic Acids in Water-Formamide Mixtures

Abstract

The enthalpies of solution of N,N-disubstituted amides of formic and acetic acids at 298.15 K throughout the entire range of compositions of the water-formamide mixed solvent were measured. The enthalpies of solvation and transfer of the amides from water into the mixed solvent were calculated. The effects of the structure and properties of the solutes and also of the composition of the mixed solvent on their thermochemical characteristics were considered. The monotonous weakening of solvation of the alkylamides throughout the entire range of mixture compositions results from reduced exothermicity of their nonspecific and specific solvation. Analysis of the deviations of the enthalpies of transfer from additivity in composition showed that the hydrocarbon radicals of the amides are slightly more solvated by formamide, while the polar functional groups, by water.