Study of the Thermochemical Aspects of the Dissolution and Solvation of Certain β-Alanyl-Dipeptides in Aqueous Solutions of Formamides at a Temperature of T = 298.15 K

This paper presents, for the first time, the standard values of the enthalpies of β-alanyl-l-histidine (β-Ala-L-His) dissolution (Δ_solH⁰) in the binary solvents water + (formamide, N-methylformamide, and N,N-dimethylformamide) at T = 298.15 K, obtained calorimetrically. Various parameters such as solvation enthalpies, (Δ_solvH⁰), transfer enthalpies, (Δ_trH⁰) and the enthalpic coefficients of pairwise interactions (h_xy) were calculated from these values. The obtained data were compared with similar data for β-alanyl-β–alanine (β-Ala-β-Ala). A similar character of solvation of both peptides in mixtures of the same name has been established. This is evidenced by the linear relationship between the enthalpic coefficients of the pairwise interactions of both peptides. The solvation of peptides is weakened in the series of mixed solvents (H₂O + FA) < (H₂O + NMF) < (H₂O + DMF), which is associated with an increase in the hydrophobic properties of the formamides and an increase in the intermolecular interactions in the mixtures themselves in the same order. However, β-Ala-L-His is more strongly solvated than β-Ala-β-Ala. This is due to the presence of specific solvation centers in the side chain of β-Ala-L-His.