NMR Study of Rotational Barriers and Conformational Preferences. II. d11-Cyclohexane

The rate of conformational isomerization of cyclohexane has been measured over the temperature range —75.0 to —47.0° by observation of the NMR spectrum of C6HD11, which is much simpler than that of cyclohexane itself and is amenable to exact kinetic treatment. The line broadening arising from D—H coupling was eliminated by double resonance. It is found that ΔF‡ is equal to ΔH‡ within experimental error for the chair-to-chair reaction and is 10.5 kcal (206.0°K) (10.2 kcal for the chair-to-boat process); ΔS‡ for the chair-to-chair process is thus about zero and for the chair-to-boat process is about +1.4 eu.