Proton Magnetic Resonance Studies of 2-Methyl-2-Propanethiol

Proton magnetic resonance (PMR) studies of 2‐methyl‐2‐propanethiol reveal the existence of molecular reorientation (activation energy ∼ 3 kcal/mole) about the C–S axis in the low‐temperature phase (phase IV). This type of molecular reorientation is in accord with Kondo's dielectric studies of phase IV. General molecular reorientation and self‐diffusion occur in both phases II and I. The self‐diffusion activation energies in the two phases (∼ 8.5 and 7.7 kcal/mole) are in agreement with estimates from the model of Andrew. Self‐diffusion is found to be somewhat quenched upon transition from phase II to phase I; this behavior can be explained on the basis of a change of lattice structure from bcc (proposed by Guthrie and McCullough) to fcc (found experimentally by Kondo). The PMR studies can not distinguish between phases III and II. The rigid‐lattice second moment (at $\text{T\hspace{0.17em}<\hspace{0.17em}70°}\mathrm{K}$ ) is in accord with a molecular structure based on standard bond lengths and angles.