TRADITIONAL AVERAGING OF NMR PARAMETERS IN THE FAST EXCHANGE LIMIT ISVALID

Weitekamp and co-workers have recently questioned the traditional meth od of averaging NMR parameters such as chemical shifts and coupling co nstants in the fast exchange limit because this method neglects spin e nergies. They have presented an alternative averaging method in which the spin energies are included in an equilibrium statistical mechanics treatment. We believe that this alternative method is not applicable to resonant measurements, such as NMR, and show that it is not in agre ement with certain extant experimental data. We point out that the tra ditional method is correct in its neglect of spin energies and show th at it is in agreement with these experimental data.