DFT study of molecular structure of 2-oxo-1,2,3,4-tetrahydropyrimidin-5-carboxamides and their corresponding oxidized forms 2-oxo-1,2-dihydropyrimidin-5-carboxamides

Density functional theory (DFT) at B3LYP/6-31++G** level has been applied to study structural, electronic and bonding characteristics of some 2-oxo-1,2,3,4-tetrahydropyrimidin-5-carboxamides (THPMs) and their oxidized forms 2-oxo-1,2-dihydropyrimidin-5-carboxamides (DHPMs). Results of this study show that for these THPMs, the six-member ring adopts a boat conformation with a pseudo-axial orientation of the C4-substituent. Experimental and theoretical 1H NMR data obtained for THPMs and their corresponding oxidized forms (DHPMs) are correlated. Thermochemical analysis on THPMs and their corresponding oxidation products show that the oxidation reaction of THPMs to DHPMs is endothermic.

► Structural, electronic and bonding characteristics of title compounds are studied using DFT- B3LYP/6-31++G∗∗ method.
► Results show that the ring in THPMs adopts a boat conformation with a pseudo-axial orientation of the C4-substituent.
► In two cases, we obtained X ray crystal structure data and the theoretical and experimental data have been compared.
► Experimental and theoretical 1H NMR data obtained for THPMs and their corresponding oxidized forms (DHPMs) are correlated.
► Thermochemical analysis on THPMs and the oxidation products show that the oxidation reaction of THPMs to DHPMs is endothermic.