Evidence for short-range orientation effects in dipolar aprotic liquids from vibrational spectroscopy. Part 2.—Carbonyl compounds

Abstract

In the Raman spectrum of pure liquids, the anisotropic component of the CO stretching band falls at a higher frequency than the isotropic component. In the same liquids the infra-red band maximum appears at almost the same frequency as the Raman anisotropic component. In some cases the infra-red band may be resolved into two components, the stronger coinciding with the anisotropic, the weaker with the isotropic Raman band. These effects disappear with dilution and are reduced with increasing temperature.

This behaviour is explained in terms of a model which assumes that dipolar aprotic liquids are composed of clusters of molecules oriented in an (at least partially) ordered way.