Studies of chemical exchange by nuclear magnetic relaxation in the rotating frame

Abstract

The exchange of protons between sites with different chemical shift is studied by means of N.M.R. relaxation time measurements (T 1ρ ) in the presence of an r.f. magnetic field. The system studied is chair-to-chair isomerization in cyclohexane. The exchange rate and chemical shift are measured in the temperature range 215°k to 250°k. The method is compared with other N.M.R. techniques for studying chemical exchange and is found to have advantages particularly at high exchange rates.