Nature of the Hydrogen Bond. III. The Measurement of the Infrared Absorption Intensities of Free and Hydrogen-Bonded OH Bands. Theory of the Increase of the Intensity Due to the Hydrogen Bond

Abstract

The integrated intensities of the infrared OH bands of various compounds have been measured for the free and the hydrogen‐bonded states. It is found that the integrated intensity of either the free or the hydrogen‐bonded OH band increases as the frequency decreases. It is concluded that the main factor increasing the integrated intensity of the intermolecularly hydrogen‐bonded OH bands is the charge transfer through the hydrogen bond. The sign of the change of the dipole moment of the free phenol with the OH distance is discussed. An explanation is given for the weakness of the OH bands of the chelate compounds.