Spectroscopic Studies of the Hydrogen Bond. II. The Shift of the Osngbnd;H Vibrational Frequency in the Formation of the Hydrogen Bond

摘要

The association spectra of a number of acids and alcohols in the region &lgr;&lgr;9000–11,000 have been observed both in solution and in the pure liquids. In each case a broad band with maximum near &lgr;10,000 was observed while in the alcohols an additional weaker band near &lgr;9000 appears to be present. Evidence is presented that the &lgr;10,000 band is to be identified with the O&sngbnd;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&sngbnd;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&sngbnd;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&sngbnd;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&sngbnd;H vibrational frequency is pointed out and its use is suggested in the interpretation of certain spectra.