Thermochemical investigation of glycyl-L-alanine dissolution in aqueous solution of some acetamides and formamides at T = 298.15 K (Similarities and differences)

Abstract

The paper presents data on the glycyl-L-alanine dissolution enthalpies in aqueous solutions of formamide (FA), N-methyl-formamide (MFA), N,N-dimethylformamide (DMF), acetamide (AM), N-methyl-acetamide (NMA), and N,N-dimethylacetamide (DMA) at an organic co-solvent concentration x2 = 0 ÷ 0.25 - mole fraction and T = 298.15 K, obtained by calorimetry. The standard values of dissolution enthalpies (ΔsolHo), transfer enthalpies (ΔtrHo), and enthalpic coefficients of pairwise interaction (hxy) were calculated from these data. The dependences of the enthalpic characteristics of glycyl-L-alanine dissolution on the mixture composition and the interaction energy between the mixture components have been established. A comparative analysis of the values of the enthalpic coefficients of pairwise interactions of glycyl-L-alanine, glycyl-glycine, and glycyl-L-tyrosine in similarly mixed solvents has been carried out. A quantitative assessment of the enthalpy contributions of the side-chains of glycyl-L-alanine and glycyl-L-tyrosine to the energetics of interaction with amide molecules in an aqueous solution is given.