High‐field magnetic resonance studies of tert‐butanol in liquid and solid phases

Abstract 1H and 13C line widths and 1H, 2H, 13C and 17O spin–lattice relaxation (times (T1) of tert‐butanol (TB) were studied at a field strength of 9.4 T in the liquid and solid states (160–299 K). The NMR line width data reveal the existence of at least two crystalline forms between 160 K and the metling point (299 K). The ordered phase (solid II) is observed throughout the whole temperature region on warming, indicating that the disordered phase (solid I), observed between ca. 210 K and the melting point, is monotropic. The line narrowing of the 1H resonances for solid I, observed around 225 and 280 K, is ascribed to the onset of overall molecular tumbling and translational diffusion, respectively. The 1H line width of solid II is constant between 160 and 284 K. Activation parameters for the overall molecular tumbling and/or internal methyl and tert‐butyl reorientations were obtained from the T1 data. The long correlation time (75–92 ps at the melting point) and high activation energy (27–37 kJ mol−1) suggest that the overall tumbling in the disordered and liquid phases involves hydrogen‐bonded aggregates. The dynamics of the methyl group, in contrast to the tert‐butyl group, appear to be only slightly affected by change of state and phase (activation energy 11–12 kJ mol−1).