Application of the NMR Method to Rotational Isomerism. Limitations Revealed by Temperature-Dependent Studies on CHBr2–CFBr2

NMR and thermodynamic parameters for the two rotational isomers of CHBr2–CFBr2 have been obtained from their low-temperature 1H and 19F spectra. The results are in variance with those obtained from the conventional method which utilizes the temperature dependence of the time-averaged spectra at higher temperatures. Limitations of the second method have been discussed. The signs of the coupling constants in the two rotamers have been established.