Enol

An enol has an OH group bonded to a carbon of a C=C bond. Protonation and pi-bond rearrangement can interconvert it with a carbonyl compound through keto-enol tautomerism.

Interconversion of a carbonyl compound with its enol or enolate-derived forms. Reprotonation of a planar intermediate can epimerize an alpha stereocentre.

An enol stabilized by an intramolecular O–H···O interaction, commonly closing a six-membered arrangement in a 1,3-dicarbonyl compound. proton exchange between equivalent enol forms can average NMR environments.

A silyl enol ether has the connectivity $\mathrm{C}=\mathrm{C}-\mathrm{O}-\mathrm{Si}{\mathrm{R}}_3$. Nucleophilic attack at silicon can cleave the Si–O bond and generate an enolate without adding to the original carbonyl carbon.

An O-silylated ester enolate, with two oxygen substituents on one carbon of the enol double bond.