IR spectra and structure of 2-aryl-3-hydroxypyridines

The IR spectra of methyl, chloro, and phenyl derivatives of 3-hydroxypyridines in CCl₄ solutions and in the crystalline state were studied. A comparison of the frequencies, half widths, and integral intensities of the bands of the stretching vibrations of the hydroxyl groups in the spectra of solutions of the 3-hydroxypyridine derivatives in CCl₄ with the characteristic OH bands in the spectra of phenols demonstrates that 3-hydroxypyridines exist practically completely in the hydroxy form in dilute CCl₄ solutions. The shift in the OH bands in the spectra of 2-phenyl-3-hydroxypyridine derivatives indicates that the OH group forms a -hydrogen bond with the phenyl ring. The presence also of a band of a free OH group is evidence for the existence of s-cis and s-trans conformers relative to the C-O bond.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 187–190, February, 1972.