Hydroxyl spectra of o-t-butylphenols

The free hydroxyl stretching vibration in most free phenols is observed close to 3608 cm. (-1). Most previously reported intramolecular interactions shift the band to lower frequency. However in 2,6-di-t-butyl-substituted phenols it is at 3643 cm. -1. This is due to the interaction between two electropositive groups rather than between the hydroxyl proton and an electronegative group. In mono-o-t-butylphenols there are two free hydroxyl stretching bands which are attributed to two conformations of the hydroxyl g-roup relative to the t-butyl group. One band is at the same frequency-as found for hydroxyl groups in free phenols, the other is at,the frequency of 2,6-di-t-butyl-substituted phenols. From the intensities of the two bands it is calculated that about 8% of the molecules are in the higher frequency configuration when the 6-position is free and about 17% are in the same form when a methyl group is in the 6-position. Data axe included from. both the 3600 cm. fundamental hydroxyl region and the 7100 cm, (-1) first overtone region.