Abstract
The semiempirical Pariser-Parr-Pople SCF method combined with configuration-interaction has been applied for calculation of the electronic spectrum, ionization potential and electron affinity, π-electron distribution and total π-energy of such heterocycles as oxazole, isoxazole, oxadiazoles, imidazole, pyrazole, triazoles and their monobenzo-derivatives, and the theoretical results have been compared with the available spectral data and miscellaneous chemical properties including the position-dependency on substitution reactions, novel photochemical isomerization of several compounds and so forth.