Carbon‐13 spin–lattice relaxation of tropane alkaloids. Anisotropic rotational motion of tropine and pseudotropine

Abstract

The I3C spin-lattice relaxation times of tropine and pseudotropine have been measured in CDCI3 as a function of concentration. m e same relative increase in concentration serves to increase the relaxation rates much less in the region 0.9-5.0 wt.% than in the region 5.0-14.3 wt.%. The rotational diffusion coefficients have been calculated from the relaxation data using Woessner's anisotropic rotational *ion model. Reorientation of both molecules is shown to be moderately anisotropic. The principal axes of the rotational difinsion tensor in the symmetry plane of both molecules are rotationally shifted from the principal axes of the moment of inertia tensor of the free molecules, and the main rotational axis is parallel with a l i e passing through the centre of mass of the molecule and the nitrogen atom.