The tautomeric forms of a compound differ only in the position of a proton. Due to the low energy barrier of tautomerization, tautomers exist in dynamic equilibrium in solution, the gas phase, and under certain condition in the crystalline state.

Z. Wojnarowska and co-workers, University of Silesia, Poland, have investigated the tautomerism of glibenclamide (GCM), a sulfonylurea-based drug used for the treatment of type II diabetes, by using broadband dielectric spectroscopy (BDS).

In addition to proving BDS is a good technique for monitoring tautomerism, the team determined the activation energy and time scale of tautomerism of GCM at various temperatures and conditions. This gives relevant data for determining the expiration date as well as the best storage conditions of GCM and other drugs.

• On the kinetics of tautomerism in drugs: New application of broadband dielectric spectroscopy
  Z. Wojnarowska, P. Wlodarczyk, K. Kaminski, K. Grzybowska, L. Hawelek, M. Paluch,
  J. Chem. Phys. 2010, 133, 094507.
  DOI: 10.1063/1.3475688