Application of the Forsén–Hoffman spin-saturation method and 13C nuclear magnetic resonance spectroscopy to the determination of the barrier to ring inversion in cis-1,2-, trans-1,3-, and cis-1,4-dimethylcyclohexane

Abstract

One reason for the inaccuracy of many n.m.r. determinations of activation parameters of exchange is the inaccuracy of rates of exchange determined well away from the coalescence temperature. Such errors can be minimised by using a second method, the Forsén–Hoffman spin-saturation method, to determine accurately the rate of exchange at a considerably lower temperature and by using the greater separation of resonances often found in ¹³C n.m.r. spectra. This approach is tested on ring inversion of cis-1,2-, trans-1,3-, and cis-1,4-dimethylcyclohexanes.