INFRARED SPECTRA OF COMPLEXES OF 4-PYRIDONES

Abstract

The infrared spectra of many complexes of Lewis acids with some 4-pyridones have been recorded. Large shifts to lower frequencies of about 100 cm⁻¹ have been observed in a band near 1560 cm⁻¹ as the Lewis acid strength increased. Much smaller shifts of about 5 to 10 cm⁻¹ in a band near 1640 cm⁻¹ were noted. The former band has therefore been designated as the carbonyl frequency, and the latter as a ring mode involving CC stretching.The donor site of 4-pyridones is therefore the carbonyl group, and not the nitrogen atom. Protonated 4-pyridones have similar spectra, and are consistent with O-, not N-protonation.