Thermodynamic Properties of 6-Methyl-2-oxo-4-aryl-1,2,3,4-tetrahydropyrimidine-5-carboxylic acid Esters

Abstract

Combustion energies of esters (ethyl 6-methyl-2-oxo-4-phenyl-1,2,3,4-tetrahydropyrimidine-5-carboxylate; ethyl 6-methyl-4-(4-methylphenyl)-2-oxo-1,2,3,4tetrahydropyrimidine-5-carboxylate; ethyl 4-(4-methoxyphenyl)-6-methyl-2-oxo-1,2,3,4-tetrahydropyrimidine-5carboxylate and ethyl 4-(6-methoxyphenyl)-6-methyl-2oxo-1,2,3,4-tetrahydropyrimidine-5-carboxylate) were experimentally obtained using a bomb calorimetry. According to the experimental data, the enthalpies of combustion and the enthalpies of formation in a solid state were calculated. Derivative analysis was used to investigate the compounds within the temperature range of 483.0-577.5 K. The enthalpies of fusion, vaporization and sublimation were calculated using the results of the differential thermal analysis. According to the obtained data, the enthalpies of formation of the investigated compounds in the gaseous state were calculated. The possibility of using the Benson additive scheme to calculate the enthalpy of formation is demonstrated.