Molecules that can adopt multiple conformations may show multiple peaks in NMR spectra. One way to test if the extra peaks in your spectrum are due to conformational isomers is to change the temperature. Changing the temperature will change the rate of exchange between the conformations and alter the chemical shifts. In addition to confirming the cause of the extra peaks variable temperature NMR may also provide thermodynamic information. An example based on the thyroid hormone thyroxine is described below.
