enolized

Enolized refers to a molecule that has adopted the enol tautomer of a carbonyl compound, or has been converted into its enolate form under basic conditions. Enolization is the keto–enol tautomerism, a reversible interconversion between a carbonyl compound (aldehyde or ketone) and its enol form, characterized by a vinyl alcohol structure C=C–OH. The enol form exists in equilibrium with the keto form and is stabilized by resonance with the carbonyl group.

In basic media, removal of an α-hydrogen gives an enolate anion, which can be protonated to yield the corresponding enol; in acidic media, protonation of the carbonyl oxygen increases α–hydrogen acidity, allowing deprotonation to furnish the enol. The relative amounts of enol versus keto depend on the substrate, substituents, solvent, temperature, and pH. Substrates with acidic α-hydrogens and stabilizing conjugation (e.g., β-dicarbonyl compounds) display greater enol content; simple aldehydes and ketones often reside predominantly in the keto form.

Enolization is a key step in many reactions: enolates serve as powerful nucleophiles for carbon–carbon bond formation in aldol condensations, alkylations, and Michael additions, while enol is employed directly or via masked forms such as silyl enol ethers to control reactivity. In biochemistry and catalysis, enzymes and acids/bases can accelerate enolization, affecting reaction pathways. The term enolized is thus used to describe molecules in which alpha-proton removal or enol formation has occurred, resulting in the enol or enolate species.