For citation: Ivanov E.V., Krasnov A.V., Petrovskaya S.G. Some thermodynamic characteristics of «thiomebicar» (2,4,6,8-tetramethyldithioglycoluril). <...> Проведен сравнительный анализ полученных данных с таковыми для известного лекарственного средства «мебикар» (2,4,6,8-тетраметилгликольурил) ‒ карбонильного аналога с выраженным транквилизирующим действием. <...> Вып. 12 SOME THERMODYNAMIC CHARACTERISTICS OF «THIOMEBICAR» (2,4,6,8-TETRAMETHYLDITHIOGLYCOLURIL) Using the differential scanning calorimetry and mass spectrometry (in combination with a Knudsen effusion method), the enthalpies of fusion and sublimation for the promising bioactive preparation «thiomebicar» (2,4,6,8-tetramethyldithioglycoluril) have been estimated. <...> A comparative analysis of the obtained data with those for the well-known pharmatseutical «mebicar» (2,4,6,8-tetramethylglycoluril), being a full carbonyl-substituted analogue possessing the pronounced tranquilizing effect, has been carried. <...> Key words: 2,4,6,8-tetramethyldithioglycoluril, melting point, fusion heat, sublimation standard enthalpy INTRODUCTION The heterocyclic molecules of a general formula (CH)2[(NR)2CX]2 where R ≡ H or Alk and X ≡ O or S, consisting of two close-to-planar fivemembered rings and HC−CH-bridging (glyoxalic) moiety, are known as N-alkyl-substituted glycoluril or thioglycoluril derivatives [1-3]. <...> Let us say, the commercial drug mebicar (adaptol) based on 2,4,6,8-tetramethylglycoluril is well-known daytime tranquilizer [6, 7]. <...> The properties of N-tetramethylated dithioglycoluril or thiomebicar (see in Figs. 1a,b) are still poorly studied although this compound seems not less interesting with scientific and applied viewpoints. <...> Meanwhile, the lack of reliable data on its thermodynamic properties in both the crystalline and dissolved state does not allow identifying the interaction-related peculiarities of pharmacophore centers (hydrophobic and donoraccepting groups) of a molecule in question. <...> Seen in this light, we consider it would be inа teresting to assess the influence of C=O → C=S substitution on some thermodynamic characteristics (such as the molar enthalpies of sublimation, ΔsubHn0, and fusion, ΔfusHn0, as well as melting point, tm.p.) of N-tetramethylglycoluril, based on the previously derived data for mebicar [10]. <...> Molecular structures of the thiomebicar (а) and mebicar (b): a projection, being parallel to the bicycle plane) Рис. 1. <...> Структуры молекул тиомебикара (а) и мебикара (b): вид проекции, параллельной плоскости бицикла) (C8H14N4S2; molar mass: 230.3589 g·mol-1) was synthesized in the Laboratory of nitrogen-containing compounds of N.D. <...>