upsilon(O-H) absorptions and conformations of epimeric 1-tetralols and chroman-4-ols

The O-H stretching IR absorptions of epimeric 1-tetralols and chroman-4-ols were, examined in dilute carbon tetrachloride solutions. The absorption pattern was found to be related to the conformation of the hydroxyl group; the epimers with the quasi-axial OH group showed a singlet v(O-H) at 3618 cm(-1), while those with the quasi-equatorial hydroxyl had doublet absorption at 3622 and 3600 cm(-1). Based on these findings 1-tetralol itself was shown to exist preferentially in the OH axial conformation. The bands at 3618 and 3600 cm(-1) were assigned severally to the hydroxyl groups bonding to the pi-electrons on the benzene ring. When an additional aryl group is present beta to the hydroxyl, another O-H center dot center dot center dot pi bonding to the aryl group becomes possible in addition to that between the OH group and the benzene ring of the tetralin and the chroman skeletons. The conformation of the aryl substituents was deduced by applying the empirical correlation relating the geometry of the molecule to the bonded v(O-H) frequency in a wide variety of aromatic alcohols which incorporate beta-arylethanol moiety.