MOLECULAR ASSOCIATION AND MOLECULAR ROTATION IN LIQUIDS

This article concerns the effect of molecular association on the rotary motions of molecules in the liquid state. It is found that two different types of association can be distinguished: (1) In some instances, association involves the formation of polymolecular aggregates, or complexes, that move as a unit. (2) Alternatively, association may involve only correlations in the positions of different molecules, and it may have little effect on molecular motion. The difference between these two cases is analyzed. NMR spin-lattice relaxation studies of various chloroform systems are offered to illustrate these effects. Some of the experimental results suggest that molecular rotation takes place by large-angle jumps rather than by small diffusive steps against a viscous force.