Keto-Enol Tautomerism Tautomers are constitutional isomers The enol tautomer sometimes predominates when it can be stabilized by conjugation or by intramolecular hydrogen bond formation Nonacidic 0: H H:0: Base H HH H H H H Acidic Enolate ion Tautomers are constitutional isomers ▪ The enol tautomer sometimes predominates when it can be stabilized by conjugation or by intramolecular hydrogen bond formation Keto-Enol Tautomerism