The spectra and structures of the cations and anions of substituted 2-hydroxypyridines (1,2-dihydro-2-oxopyridines)

Abstract

The infrared spectra of the hydrochlorides and hexachloroantimonates of 2-hydroxy- and 2-methoxy-pyridines containing substituents (3-, 4-, 5-, and 6-Me; 3-, 5-, and 3,5-Hal; 6-OH) and the ultraviolet spectra of the cations have been determined. The former cations are 2-hydroxypyridinium ions. Hydrogen-bonding by the 2-OH proton seems to be responsible for the abnormally high infrared intensity of the skeletal stretching band near 1640 cm.^–1, which, in the past, caused it to be mistaken for a carbonyl stretching band. The infrared, ultraviolet, and, where possible, Raman spectra of the sodium salts of the above substituted 2-hydroxypyridines have also been determined. The anions seem to have normal pyridoxide structures, with the negative charge mainly on the oxygen atom (and not on nitrogen, as had previously been suggested).