STUDIES OF RATES OF CONVERSION AND POPULATIONS OF VARIOUS CONFORMATIONS OF SATURATED RING COMPOUNDS BY N.M.R.: I. CHLOROCYCLOHEXANE AND BROMOCYCLOHEXANE

Abstract

The populations of equatorial and axial halogen forms of chloro- and bromo-cyclohexane have been studied by proton magnetic resonance between 25° and −104 °C in carbon disulphide solution. From the equilibrium constants obtained the free energy change between the two conformations is obtained. The bromo compound has 82% of the equatorial halogen form and the chloro compound 77%. Estimates of the populations are also available for room temperature from the chemical shift measurements. The energy barrier for conversion between the two forms is approximately 10,850 calories. A simple Lennard-Jones potential with the available estimates of van der Waals radii is used to calculate the differences in energy of the two forms.