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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.
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. Change 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.