Studies on the Infrared Spectra of Heterocyclic Compounds. VI. Infrared Spectra of Substituted α-Pyridones and α-Quinolones. (1). The Region from 2000 to 4000cm^-1.

Abstract

The infrared spectra of a number of substituted α-pyridones and α-quinolones were investigated in the region of 2000 to 4000cm^-1, and the characteristic behavior of NH absorption in α-pyridone structure was pointed out and discussed in terms of the mode of molecular association. Extremely complex and broad nature extending from 3300 down to 2400cm^-1 of the bonded NH absorption was interpreted as being due to the extreme strength of intermolecular hydrogen bond associated through a cyclic dimer. Abnormal stability of the dimer, being approximately equal to that of carboxylic acid dimer, was pointed out and discussed in terms of resonance stabilization. Ratio of v_NH/v_ND for strongest maxima was found to be 1.27 to 1.30 and 1.34 to 1.36, respectively, for dimeric and non-dimeric α-pyridone structure. Characteristic behavior in 8-substituted carbostyrils was also pointed out.