predicted by molecular mechanics calculations. Restricted rotation of the aryl groups also has been observed by dynamicNMR spectroscopy in this compound and in a number of analogously substituted norbornanes. The aryl−norbornane bond rotation barriers were measured by line shape analysis of the 13C NMR spectra obtained at temperatures lower than −100 °C and were found to cover the range 6.0 to 7.9 kcal mol-1