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 Kendo'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 fee (found experimentally by Kondo). The PMR studies can not distinguish between phases III and II. The rigid-lattice second moment (at r<70°K) is in accord with a molecular structure based on standard bond lengths and angles.