NMR relaxation study of molecular motions in liquid chlorobenzotrifluorides

The temperature dependences of the ¹H and ¹⁹F nuclear spin-lattice relaxation times T₁ in liquid o-, m-, and p-chlorobenzotrifluorides have been measured. The analysis of the temperature dependences of the ¹H spin-lattice relaxation times leads to the conclusion that the overall molecular reorientational motion in o-, m-, and p-benzotrifluorides is nearly the same. Data for ¹H and ¹⁹F spin-lattice relaxation times of o-chlorobenzotrifluoride jointly lead to the determination of the individual contributions to relaxation rate in the entire temperature range studied. A knowledge of these contributions for o-chlorobenzotrifluoride, together with the assumption of equal correlation times for overall molecular reorientation in o- and p-chlorobenzotrifluorides, leads to the determination of the spin-internal-rotation interaction contribution to relaxation for p-chlorobenzotrifluoride in the same range of temperature.