Spectroscopic data pyridones

Table II Relative Fluorescence and Spectroscopic Data for Pyridone Sulfonates...

No attempt will be made here to review and correlate the large number of ultraviolet, infrared, nuclear magnetic resonance, and mass spectra that have been recorded, interpreted, and used in structure determination of pyridinols and pyridones. Articles that contain significant spectral data and/or discussions are noted in the Tables. The role of spectroscopic techniques, ionization constants, and dipole moments in the studies of structure and tautomerism of heterocyclic compounds has been reviewed recently by Albert. Although ionization constants have been used to estimate pyridinol-pyridpne equilibrium constants with some success, caution must be exercised about drawing conclusions from this type of data. ... 

The conclusions to be reached from these data are, chiefly, that whilst hydroxy-and mercaptopyridines and pyridine carboxylic acids exist predominantly in the Z forms (i.e. as pyridones, pyridthiones and zwitterions), aminopyridines prefer the NM forms (that is, they are mainly amines and not iminesj. The spectroscopic evidence supporting these conclusions has already been discussed, and this tautomerism is further discussed below. 

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