Comparison of ab initio calculated and experimental methyl-top moments of inertia

The methyl-top moments of inertia and planar moments of inertia of a large number of compounds have been obtained from rotational spectroscopic data and are compared with the corresponding quantities obtained from ab initio geometries. Ab initio geometry refinements have been performed with the 4-21G basis set using standard gradient techniques. High correlation is found between the spectroscopic and calculated values, indicating the possibility of using experimental methyl-top moments of inertia as a source of structural information on methyl groups.