Spectroscopic Studies of the Hydrogen Bond. II. The Shift of the O[Single Bond]H Vibrational Frequency in the Formation of the Hydrogen Bond

Abstract

The association spectra of a number of acids and alcohols in the region lambdalambda9000–11,000 have been observed both in solution and in the pure liquids. In each case a broad band with maximum near lambda10,000 was observed while in the alcohols an additional weaker band near lambda9000 appears to be present. Evidence is presented that the lambda10,000 band is to be identified with the O[Single Bond]H group. This evidence includes the behavior of the association band with change in concentration and temperature and its presence in several substances in which absorption other than that due to the O[Single Bond]H group is practically absent in the region studied. New evidence is given that a weak intermolecular hydrogen bond is formed between acetone and methyl alcohol. It is pointed out that the presence of absorption in the narrow O[Single Bond]H bands is not to be taken as evidence of the absence of hydrogen bonds in case the absorption is weak. The character of the O[Single Bond]H absorption in the case of intermolecular hydrogen bonds is discussed and the probable nature of the spectrum in the case of an intramolecular bond is indicated. A relation between the energy of the hydrogen bond and the shift of the O[Single Bond]H vibrational frequency is pointed out and its use is suggested in the interpretation of certain spectra.