Intramolecular Interaction between Hydroxyl Group and π-Electrons. IV. Rotational homers of Alcohols and Shift of νO–H Absorptions in Phenyl Substituted Alcohols

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Abstract
The authors observed symmetric νO–H absorptions for methanol and tertiary alcohols and unsymmetric bands for primary and secondary alcohols. The unsymmetric band was divided into two bands, assuming that the band is an overlap of the two symmetric bands. The idea of the rotational isomerism was successfully introduced for assigning the band and the following points were concluded. 1) Types I and IV show absorption bands at 3644∼3636 cm−1, type II at 3626∼3629 cm−1, type III at 3615∼3618 cm−1, type V at 3616∼3619 cm−1, type VI at 3608∼3611 cm−1, and type VII at 3613∼3617 cm−1. 2) The exception is dialkylphenylcarbinols which show the νO–H absorptions at about 3620 cm−1 and 3608 cm−1, the former being assigned to type III and the latter to type VII. This ruling-out may be attributed to the steric effect and the rotation around the CPh–Cα axis. The steric effect on the integrated intensities and on the wave number where νO–H absorption falls is also discussed. The differences between types II and IV and between types III and VI were attributed to the existence of the intramolecular interaction between the hydroxyl group and π-electrons of the benzene nucleus. The same reason may cause allyl alcohol to show its main νO–H absorption at about 3620 cm−1.