Intermolecular forces and solvent effects. Ill

The shifts of frequency of two vibration bands of carbon dioxide in different solvents have been measured. The results cannot be explained satisfactorily in terms of the simple model of an oscillator in a continuous dielectric medium, but suggest that intermolecular forces are dominant. In non-polar solvents dispersion forces appear to account very well for the observed shifts, and attempts have been made to explain the behaviour in polar solvents by additional dipole-induced dipole forces. The carbonyl group vibration in several solutes has been measured in a number of solvents not containing hydrogen, and considered in relation to data in other solvents. Here again, intermolecular forces seem to play a greater part than a bulk dielectric effect. Aggregations of the type C = 0 . . .X— C, in which X is a halogen, appear to occur and suggestions are made to explain the occurrence of shoulders and anomalous band contours which have sometimes been found in terms of different types of solute-solvent interaction occurring simultaneously.