Tautomerism

Chemistry Tautomerism is the existence of two functional isomers in equilibrium.

Tautomerism is a sort of dynamic isomerism shown by certain unstable molecules which change in structure. Different equilibrium structures can be formed when a hydrogen atom migrates, e.g. in the hydrocyanic acid molecule (H-CN and HN-C can co-exist).

The ketone-enol equilibrium is also an example of tautomerism, with the ketone H₃C-(C=O)-CH₃ and the enol H₃C-(C-OH)=CH₂ being in equilibrium.