Infrared spectra of hydroxynaphthalenes

Abstract

Infrared spectra of the two naphthols and nine naphthalenediols are presented in the region 4000-400 cm-1 for the solid state and 1600-900 cm-l for benzene, aqueous, and methanol solutions. By comparisons of frequency shifts resulting from change in the state or solvent, absorptions arising from the hydroxyl substituents have been located. As in phenol, the OH in-plane deformation in naphthols occurs near 1180 cm-l and is shifted to 1200 cm-l by association. Other bands near 1380 and 1220 cm-1 can be classified as α- or ,β-type because of an apparent correlation of their frequency with substituent position. Dissociation of the compounds has been followed spectroscopically in methanol solutions. Some features of the aqueous solution spectra of 1,3-dihydroxynaphthalene are shown to be consistent with the previously established keto-enol tautomerism of the monoanion.