Restricted Rotation Involving the Tetrahedral Carbon. XXV. Barriers to Exchange between <i>dl</i> and <i>meso</i> Forms of 9-(Arylmethyl)triptycenes

Abstract

Abstract Barriers to exchange between dl and meso forms via rotation about the C9–Csubst bond of 9-(arylmethyl)-1,4-dimethoxytriptycenes are obtained by the use of the methoxyl signals in the 1H NMR spectra. It is found that, although the population ratios are affected by the substituent in the 9 position, the enthalpy of activation for the rotation is almost invariant at ca. 10 kcal/mol.