The Raman spectral bandwidths of two A,' vibrations of 1,3,5trifluorobenzene (TFB) were measured in the neat liquid as a function of temperature and in the solvents CH,CI, and CS,. The Raman and 1R linewidths of two E modes were also measured in solution. Derived values of the two rotational diffusion constants, D , and D,, , were compared with the predictions of several current theories. It was observed that the Hynes-KapraCWeinberg (HKW) theory is superior to both the microviscosity-free rotor and Hu-Zwanzig 'slip' models of reorientational diffusion. Calculated values of D , and D , , for TFB in solution using the HKW model are in excellent agreement with the experimentally measured diffusion constants

The "C spin-lattice relaxation times and nuclear Overhauser enhancements of protonated carbons in 1,3,5-tribromobenzene were measured in a number of solvents of widely varying viscosity. Derived reorientational correlation times were found to increase approximately linearly with solution viscosity, as predicted by hydrodynamic theories of rotational diffusion.Rotational correlation times calculated from the Perrin stick model were two to three times longer than the measured t, values. Similarly, correlation times predicted by the Hu-Zwanzig slip model were too small by a factor of two. On the other hand, application of the newer HynesKapraI-Weinberg theory furnished reorientational correlation times that were in virtually quantitative agreement with the experimental results.