Molecular Structures and Motions in Solid Hexamethylethane by Proton Magnetic Resonance

Proton magnetic resonance (PMR) studies of solid hexamethylethane reveal the existence of C3′ reorientation of the t-butyl groups (activation energy ∼ 3 kcal/mole) in the low-temperature phase. As the temperature is raised above the transition temperature (152.5°K) general molecular reorientation sets in abruptly. A further temperature increase leads to a gradual line narrowing due to self-diffusion above 270°K. The activation energy for self-diffusion is 15.0 ± 0.3 kcal/mole. The rigid lattice second moment (T < 80°K) is in accord with a molecular structure based on standard bond lengths and angles.