The structures of furazans and furoxans
The IR spectra of furazans and furoxans are characterized by lowered values of frequencies and of integrated absorption band intensities for the C=N bands. The peculiarities of the UV absorption spectra of these compounds are similar to those of pyridine and its benzene analogs in comparison with the corresponding N-oxides. Comparison of the results with those given in the literature regarding chemical properties, delocalization energies, X -ray spectra, and quantum chemistry calculations leads to a conclusion that the 2, 1, 3-oxadiazole ring possesses a definite aromaticity.