THEORETICAL-STUDY OF ELECTRONIC-STRUCTURE AND PROPERTIES OF SOME 5-MEMBERED HETEROCYCLIC-COMPOUNDS - PYRAZOLE, IMIDAZOLE, FURAN, ISOXAZOLE, 1,2,5-OXADIAZOLE AND 1,3,4-OXADIAZOLE

Results of ab initio SCF calculations employing a gaussian basis set of molecular double-zeta quality are reported for pyrazole, imidazole, furan, isoxazole, 1,2,5-oxadiazole and 1,3,4-oxadiazole. Several physical properties of these molecules have been calculated and compared with experimental and other theoretical values where available. Calculated molecular properties include: dipole moment, quadrupole moment, average diamagnetic shielding, diamagnetic susceptibility, electric field gradient and nuclear quadrupole coupling constant. Reorganization of the electronic charge densities upon ionization has been studied by comparing the electron populations and the charge density contour diagrams between the ground state and the corresponding cation. Results obtained from the PRDDO calculations have been compared with the ab initio values. Good agreements in the molecular orbital energies have been found. The ionization potentials obtained using Koopmans' theorem are correlated with the experimental values from photoelectron spectroscopy. © 1979.