Thermodynamics of Non-Covalent Interactions of Benzylamine with Organic Non-Electrolytes: Calorimetry of Solution

Study of hydrogen bonds with the participation of nitrogen-containing molecules is important for the chemistry of biologically active substances, since the XH. N and NH. X hydrogen bonds have an impact on their properties and supramolecular structure. As far as the study of hydrogen bonding in biomolecules is a complicated problem, their model compounds such as amines were studied. In this paper, the method of solution calorimetry is used for studying intermolecular interactions of benzylamine with various organic molecules. The enthalpies of dissolution at infinite dilution of benzylamine in chloroform, organic bases, and aliphatic alcohols, as well as of chloroform, organic bases, and aliphatic alcohols in the medium of benzylamine were measured. The enthalpies of specific interactions in these systems were determined on the basis of experimental data. Proton-donor and proton-acceptor abilities of benzylamine molecules were analyzed. It is shown that depending on the media benzylamine and chloroform can form complexes of different composition. It was found that the enthalpies of specific interaction of benzylamine with the bases are close to zero. The peculiarities of hydrogen bonding of benzylamine with aliphatic alcohols were studied. It is shown that the hydrogen bond between benzylamine and the alcohol clusters is 20-30% stronger than that between benzylamine and the alcohol monomer. The influence of the structure of amines on the enthalpy of specific interaction and cooperative hydrogen bonding is discussed. It is shown that the effect of the substituent at the nitrogen atom may vary considerably in the complexes of amines with different proton-donor molecules.