SOLVATION CONTRIBUTIONS OF PYRIDINE FUNCTIONAL GROUPS IN TRANSFER ENTHALPY OF AMINE FROM METHANOL TO ACETONITRILE, DIMETHYL SULFOXIDE AND DIMETHYLFORMAMIDE

Quantum-chemical calculations of the energy and structure of pyridine molecule (Py) in the free state, methanol (MeOH), acetonitrile (AN), dimethyl sulfoxide (DMSO) and dimethylformamide (DMF) have been performed using the density functional theory (DFT) at the B3LYP with the 6-31G basic set supplemented by polarization and diffuse functions and within the model of the self-consistent reactive field (PCM). It was found that the transfer of the pyridine molecule from the free state to the MeOH, AN, DMF and DMSO media leads to: an increase in bond distances only between nitrogen and carbon atoms of amine; significant changes in the charges on the carbon atoms associated with the reaction center (the growth of positive charges varies in the series: DMF = DMSO < MeOH = AN); an increase in the positive charge on hydrogen atoms, which varies in the series: MeOH = AN < DMF = DMSO. A comparative analysis of the results from quantum chemical calculations was carried out with data on transfer enthalpies of amine from MeOH to AN, DMF and DMSO (ΔtrH°(Py)MeOH → solv) which were obtained by calorimetric method. It was found that the resolvation of the nitrogen atom gives the major contribution to the change in the solvate state of pyridine when the composition of the solvent MeOH → DMF and MeOH → AN changes. In case of transfer of Py from MeOH to DMSO, contributions from the resolvation of the nitrogen atom and the hydrocarbon radical to the overall energy of the resolvation of molecule are approximately the same.Forcitation:Kuz’mina I.A., Volkova M.A., Kuz’mina K.I., Belova N.V., Sharnin V.A. Solvation contributions of pyridine functional groups in transfer enthalpy of amine from methanol to acetonitrile, dimethyl sulfoxide and dimethylformamide. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2018. V. 61. N 3. P. 4-9