2-phenylisatogen: A study of molecular dynamics using 13C NMR spin-lattice relaxation times

13C NMR spin‐lattice relaxation times (T1) were measured for 2‐phenylisatogen in CDCl3 solution. The nonequivalence of the T1 values for the various protonated carbons in this molecule indicates that molecular motion is anisotropic. Analysis of the T1 data using the Woessner formalism for axially symmetric ellipsoids yields a set of diffusion coefficients for overall and internal motion. The phenyl ring undergoes internal motion relative to the larger isatogen ring system. A variable‐temperature study of T1 behaviour in the range 301−363 K indicates that the major motions of the molecule have identical activation energies, viz. 10.5 ± 0.5 kJ mol−1, and that the ratios of derived diffusion coefficients remain constant with temperature. These results suggest that solvent interactions play a major role in controlling the motions of the molecule.