Raman effect and hydrogen bonds

Summary

The Raman spectra of a few typical aldehydes and ketones and their mixtures with acceptor solvents such as phenol, methyl and ethyl alcohols and chloroform are recorded and the results are discussed. They support the general conclusion arrived at in Part I that large variations in hydrogen bond strengths exist and that they depend upon two factors (1) the anionoid power of the donor atom and (2) the cationoid power of the acceptor atom. The question of distinguishing between two types of hydrogen bonds, the hydrogen and hydroxyl bonds, as suggested by Bernal is discussed in the light of our results. It is shown that there is justification for division into two categories and a proposal is made to effect the classification as below: (1) True Hydrogen Bonds. (2) Hydrogen Bonds. In Class (1) both the cationoid (C=O) and anionoid (OH) centres are affected whereas in class (2) only the cationoid group indicates change.

The influences of constitutive factors on the capacity of the carbonyl compounds to form hydrogen bonds are explained as due to their effect on the strength of the C=O group. Similar explanation has already been given in Part I regarding the behaviour of the solvents containing cationoid atom (H atom) in hydrogen bond formation.