Abstract
Several 3-aminoquinazolin-4-(3H)-one derivatives were synthesized and characterized. Using proton nuclear magnetic resonance (NMR) spectra, we have investigated the barriers to rotation around the N - N bond as a function of temperature. Changes in the NMR spectra at high temperatures are explained in terms of hindered rotations of the N - N bond. Free energies of activation for the rate determining stereochemical process were calculated to be as high as 67-75 kJ . mol(-1). Ground state molecular geometries and vibrational frequencies were calculated using the HF/6-31G** and B3LYP/6-31G** level of theories. The optimized bond lengths and bond angles are in good agreement with experimental values at both theoretical levels.