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Theoretical chemistry Theoretical chemistry Z 0350 Some New Views on the Tautomerization Mechanism -[107 refs.]. -(KERESELIDZE, J. A.; ZARQUA, T. S.; KIKALISHVILI, T. J.; CHURGULIA, E. J.; MAKARIDZE, M. C.; Russ. Chem. Rev. (Engl. Transl.) 71 (2002) 12, 993-1003; Dep. Chem., Javakhishvili State Univ., Tbilisi 380028, Georgia; Eng.) -Lindner 22-292

The energy characteristics of the tautomeric transformations of cytosine, thymine, and uracil have been calculated within the framework of the quantum chemistry theory of functional density. It was concluded that the directions of the tautomeric conversions are characterized by energies of activation calculated according to the theory of functional density.Prototropic tautomerism in nitrogen-containing heteroaromatic compounds has been well studied by experimental [1-4] and theoretical [5-11] methods, and general conclusions have been drawn that tautomeric keto and amino forms are canonical, the equilibrium constant depends on the structure of the compound and the solvent, and proton transfer is effected according to a cyclic dimer mechanism. Particular attention has been paid to the study of tautomeric conversions of pyrimidine bases with the aim of a qualitative description of the uncommon tautomeric forms and processes [12][13][14][15][16], and also clarification of the possibility of the existence of intermolecular hydrogen bonds [17][18][19]. Interest in the theoretical investigation of prototropic tautomeric conversions has grown with the appearance of calculating programs putting into effect the methods of the theory of functional density (TFD), which effectively reproduces the energy and electronic characteristics of complex molecular systems [20].