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

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 x(2) = 0 divided by 0.25 - mole fraction and T = 298.15 K, obtained by calorimetry. The standard values of dissolution enthalpies (Delta H-sol degrees), transfer enthalpies (Delta H-tr degrees), and enthalpic coefficients of pairwise interaction (h(xy)) 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. (C) 2021 Elsevier Ltd.