The dissertation is devoted to the study of thermodynamic properties of oxygen- and nitrogen-containing heterocyclic compounds, which have a wide range of pharmacophore properties and their solutions in a number of organic solvents.
A comprehensive thermodynamic study of individual substances and their solutions was carried out, the results of which: bomb calorimetry determined the energy and enthalpy of combustion and the formation of five furan and twenty-eight arylfuran compounds and six 1,2,3,4-tetrahydropyrimidines in the condensed state; Knudsen's integral effusion method was used to study the temperature dependences of the saturated vapor pressure above the surface of five furan and twenty-seven arylfuran substances in the solid state and for three substances in the liquid state; enthalpies of sublimation of thirty-three substances are calculated; Differential thermal and thermogravimetric methods of analysis determined the enthalpies of melting and evaporation of five furan, twenty-five arylfuran and six 1,2,3,4-tetrahydropyrimidine substances; According to the experimentally determined values of enthalpies of formation in the condensed state and enthalpies of sublimation, the enthalpies of formation of five furan, twenty-six arylfuran and 1,2,3,4-tetrahydropyrimidine compounds in the gaseous state were calculated; the thermodynamic parameters of dissolution of four furan and twenty-six arylfuran substances in acetonitrile, benzene, ethyl acetate, propan-2-ol and propan-2-ones were investigated.
Simple equations for calculating changes in the heat capacity of sublimation and evaporation processes by 298K are proposed, which are much simpler than the known calculation methods, but are not inferior to them in accuracy. The equation for calculating the enthalpies of melting is proposed according to the molecular weight of the substance, its melting temperature and specific values of the melting entropy, which are determined for different classes of substances. Using changes in heat capacity and entropy during the melting process, the equation for converting the enthalpies of melting to any other temperature is proposed.
The thermodynamic parameters of the investigated substances were calculated according to the semi-empirical calculation schemes of Benson, Lebedev-Miroshnichenko, Jobak, Kоuen, Domalsky and Salmon. Their comparison with experimental values is made and the received discrepancies are analyzed. The additive scheme of Benson and Lebedev-Miroshnichenko was replenished with new group contributions. The possibility of calculating the enthalpies of sublimation based on the results of differential thermal and thermogravimetric analysis is shown.
The method of fragment replacement for the calculation of enthalpies of formation in the condensed state has been adapted. The presence of excess energies, hydrogen bonding and dipole-dipole interactions in the investigated substances is shown.
Taking into account the enthalpies and entropies of melting, the values of enthalpy and entropy of the mixing process of the investigated substances in a number of selected solvents at 298 K were determined. The relationship between the enthalpies of mixing with the energies of dipole-dipole interactions and the hydrogen bond in solutes and solvents is shown. The presence of compensation effects of the process of dissolution of the investigated substances in the applied solvents is established.
The relationship between the melting temperature and its solubility is shown, according to which the equation for estimating the solubility by the melting temperature of a substance is proposed.
