Solvation enthalpies of formamides and acetamides in a water—glycerol mixture. Additivity of thermochemical characteristics of solutions

The solution enthalpies of formamide and N,N-dimethyl- and diethylamides of formic and acetic acids in a water—glycerol mixed solvent were measured and the solvation enthalpies were calculated. The enthalpy coefficients of amide—glycerol pair interactions in aqueous solution were calculated. The effect of the mixture composition and the structure and properties of solutes on the enthalpic characteristics were considered. The contributions of structural fragments of the amide molecules to the enthalpic characteristics of solutions were calculated in the framework of the proposed additive scheme. This made it possible to analyze the role of nonspecific and specific solvations of the amides in solution and predict the vaporization, solution, and solvation enthalpies and enthalpy coefficients of pair interactions of experimentally unstudied N-methylformamide, N-ethylformamide, N-methyl-N-ethylformamide, N-methylacetamide, N-ethylacetamide, and N-methyl-N-ethylacetamide in a water—glycerol mixture, as well as donor numbers for these amides. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1363–1370, June, 2005.