The intensity of the C=O band in the infrared spectra of some carbonyl-containing heterocyclic compounds

Summary The high values for the intensity of infrared bands of the C=O group in a number of carbonyl-containing heterocyclic compounds (pyridones, quinolones, pyrones, etc.) shows the increased polarity of the exocyclic C=O bond in these compounds. This permits us to consider them to a definite degree as aromatic compounds in the same way as is done for tropones, sydnones, and diphenylcyclopropenone.We take this opportunity to thank N. P. Posherina for kindly supplying the-pyrones.