Nuclear Magnetic Resonance Study of Exchanging Systems. IX. The Slow Rotation of the Methyl Group in Sterically Overcrowded Compounds

Abstract
In order to obtain information about the slow rotation of methyl groups, the 1H NMR spectra of 9-t-butylethenoanthracene and 9-t-butyltriptycene derivatives were measured at very low temperatures. It was found that the signals of the two methyls of the t-butyl group in these compounds show a considerable line broadening at low temperatures, and it was made clear that the rotation of the methyl groups in these compounds is strongly restricted.