Lviv Polytechnic National University
Ivan Franko National University of Lviv
Frantsevich Institute for Problems of Materials Science
Lviv Polytechnic National University
Lviv Polytechnic National University
Lviv Polytechnic National University

The derivatives of 6-methyl-2-oxo-4-phenyl-1,2,3,4-tetrahydropyrimidine-5-carboxylic acid are the simplest representatives of Bidzhenelli’s dyhidropirymidynes and are characterized by a wide range of biological activity. It is important to use pure substances at each stage of the synthesis in the pharmaceutical industry. The main method of solid substances purifying is recrystallization using the so-called "classic" solvents, which include acetonitrile. Therefore, the study of solubility and thermodynamic parameters accompanying interactions of dissolved substances with acetonitrileis important to optimize the processes in chemical and pharmaceutical industries.

Enthalpy (ΔsolH)  and entropy (ΔsolS) of dissolution were determined from the temperature dependence of the solubility of methyl ester of 6-methyl-2-oxo-4-aryl-1,2,3,4-tetrahidropirymidyn-5-carboxylic acid (ΔsolH) = 30,1±1,1 kJ/mol, (ΔsolS) = 43,4±3,3 J/mol •K, ethyl ester of 6-methyl-2-oxo-4-aryl-1,2,3,4-tetrahidropirymidyn-5-carboxylic acid (II) (ΔsolH) = 37,68±0,24 kJ/mol, (ΔsolS) = 62,97±0,70 J/mol •K, methyl ester of 6-methyl-2-oxo-4-4-methoxyphenyl-1,2,3,4-tetrahidropirymidyn-5-carboxylic acid (III) (ΔsolH) =32,24±0,78 kJ/mol, (ΔsolS) = 52,96±2,5 J/mol •K and ethyl ester of 6-methyl-2-oxo-4-methoxyphenyl-1,2,3,4-tetrahidropirymidyn-5-carboxylic acid (IV) (ΔsolH) =28,88±0,90 kJ/mol, (ΔsolS) = 39,24±2,8 J/mol •K. 

Determined values of enthalpy (ΔsolH) and entropy (ΔsolS) of dissolution include values of enthalpy ΔmixHо and entropy ΔmixSо of mixing and a phase transition of crystalline substances to the liquid phase in solution fusHо and fusSо. Fusion enthalpies of substances in kJ/mol ΔfusH487,7=32,9±1.8 (І); ΔfusH479,9=45,8±2,3 (ІІ); ΔfusH470,4=40,7±2,2 (ІІІ); ΔfusH478,9=44,3 ± 2,6 (ІV) were determined from differential thermal analysis (DTA) data obtained using derivatograph Q-1500 D and calculated to 298К ΔfusH ( kJ/mol) та fusSо (J/mol •K): 23,8±1,9, 42,9± 3,9 (І); 32,9±2,5, 61,8 ± 2,9 (ІІ); 29,3±2,4, 57,3 ± 2,9 (ІІІ) and 31,9±2,8, 60,0 ± 3,4 (ІV) respectively.

Enthalpies (ΔmixHо, kJ/mol) and entropies(ΔmixSо, J/mol •K) of mixing of investigated compounds in acetonitrile severally are^ 6,3±2,2, 0,5±4,9 (І); 4,8±2,0, 1,2±2,9 (ІІ); 2,9±2,5, -5,0±3,8 (ІІІ); -3,0±2,9, -20,8±4,4 (ІV).

The experimental and calculated data can be used to predict the reactional behavior of the substance in the solution and to optimize the purification and separation processes.


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