Direct evidence of solid-state tautomerism

Direct Evidence of Solid-State Tautomerism by Diffraction Methods... 

The chemical and crystallographic literature contains a copious amount of structure determinations where X-ray diffraction analysis has been invoked to provide direct evidence of the tautomeric form of a particular compound in the solid state. Many systematic studies of both ground-state and excited-state proton transfer processes of a larger number of tautomeric compounds or of the same compound under varying conditions have also been reported. Rather than attempting to provide a comprehensive overview of all known examples of tautomeric systems characterized by X-rays, we have selected here a handful of cases that illustrate how the method can be applied to unravel details that are relevant to the identity... 

---