High-field magnetic resonance studies of the molecular motion of tert-butyl compounds in liquid and solid phases: the binary system tert-butyl iodide–carbon tetrachloride

Abstract

The binary system tert-butyl iodide–carbon tetrachloride was studied in the liquid and solid phases using ¹H and ¹³C nuclear magnetic resonance spectrometry. An analysis of the methyl ¹H and ¹³C linewidths and spin–lattice relaxation times is reported. The ¹H linewidths in the disordered phase (solid I) are governed by ¹H–¹H dipolar interactions even in the most dilute sample (6.7 mol-%), whereas the ¹³C linewidths appear to be dominated by ¹³C–^35,37Cl interactions at all concentrations below 70 mol-%. The line narrowing of the ¹H resonances is largely caused by translational diffusion of the tert-butyl iodide (TBI) molecules, whereas translational diffusion of the CCl₄ molecules dominates the ¹³C line-narrowing mechanism in most instances. The T₁(¹³C) minimum of solid II moves to lower temperature with increasing dilution, indicating that the reorientational freedom of the tert-butyl group is enhanced by the addition of CCl₄. There is a discontinuity in T₁ at the melting-point and an abrupt change of T₁ at the transition point of the neat and dilute samples of TBI. The measured activation energies and correlation times in solid I suggest that the over-all tumbling motion of the TBI molecules in the inhomogeneous region (solute concentrations higher than 50 mol-%) is markedly retarded by the addition of CCl₄.