A nuclear magnetic resonance investigation of solid 1,3,5 cycloheptatriene. (Heat capacity)

Abstract

The lineshape and spin-lattice relaxation times have been measured in solid 1,3,5 cycloheptatriene between 50 K and the melting point. The linewidth change which occurs below the heat capacity transition point of 154 K indicates considerable molecular motion. The very low value for the second moment of the lineshape (0.8 G2) cannot be explained by any simple motion, and various possibilities are discussed. This motion is governed by an activation energy of 6.1+or-0.5 kcal mol-1. Above the transition point, where the lattice spacing is known, free quasi-isotropic reorientation is occurring, coupled with molecular diffusion at an increasing rate.