Molecular reorientations of 1-bromo- and 1-iodo-adamantanes ¹H N.M.R. relaxation study

Abstract

Second moments and spin-lattice relaxation times, T ₁ and T _1ρ, have been measured from 100 K to 400 K for the protons in powdered 1-bromo and 1-iodo-adamantanes. Analysis of these data have shown that the reorientations are uniaxial in the low temperature phases. In the high temperature disordered phase of bromo-adamantane, the reorientation is endospherical and a slow molecular translational motion also exists. In the high temperature disordered phase of iodo-adamantane the reorientation is 12-fold uniaxial, in agreement with the Incoherent Quasi-elastic Neutron Scattering (I.Q.N.S.) experiments. All the results correspond to the crystallographic structures deduced from X-ray scattering.