Topic overview

Start with the big picture

The keto form is generally more stable, while conjugation, intramolecular hydrogen bonding, or aromaticity can favor the enol. The α-hydrogen is relatively acidic because its removal produces a resonance-stabilized enolate. Tautomerization can occur under acid or base catalysis: acid activates the carbonyl oxygen, whereas base removes the α-proton before the enolate is protonated. Enolates can react at carbon or oxygen, and their formation connects tautomerism to α-substitution and condensation reactions. The topic also introduces practical consequences, including isotopic exchange, racemization at chiral α-centers, and spectroscopic approaches to distinguishing forms.