Tautomerism, Proton Transfer, and Resonance-Assisted Hydrogen Bonding

Tautomerism, Proton Transfer, and Resonance-Assisted Hydrogen Bonding 

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 

8 Direct Evidence of Solid-State Tautomerism by Diffraction Methods 

A typical example of a symmetric RAHB system is the O- H- -O bond in symmetrically substituted fS-diketones (see, for example, [5]). These compounds include a strong hydrogen bond between two close oxygen atoms. In addition to RAHB bonds (-0-H- -0=), the strong homonuclear hydrogen 

Enolones Ertaminones Enamino-lmines Enol-imines 

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