It is the phenomenon in which a single compound leads to the formation of interconvertible products that differs in the position of one atomic nucleus.
The two structures participating in tautomerism are called tautomers.
Conditions for tautomerism:
Compounds must have an electron-withdrawing atom or -I group i.e., an atom that is more electronegative than carbon and has the tendency to accept the hydrogen atom as tautomerism involves migration of hydrogen atom.
The carbonyl group must have an acidic alpha hydrogen atom i.e. there must be a carbon linked to the electron-withdrawing atom and further this carbon is linked to another carbon having a hydrogen atom.
Keto-enol tautomerism occurs in the presence of acidic/basic catalyst.
Example - keto-enol tautomerism:
“Tautomers are readily interconverted constitutional isomers, usually distinguished by a different location for an atom or a group.”
When a keto form undergoes a proton-transfer equilibrium an enol form is obtained.
