What does enol mean?
An enol is an organic compound in which a hydroxyl (–OH) group is attached directly to one of the carbon atoms of a carbon–carbon double bond. The name is a contraction coined by chemists from 'alkene' and 'alcohol,' capturing the structure's hybrid nature: it is at once an unsaturated hydrocarbon fragment and an alcohol. Enols rarely persist as stable, isolable substances — most exist only fleetingly as intermediates that rapidly rearrange into their more thermodynamically favored carbonyl counterparts, aldehydes and ketones. This reversible interconversion, known as keto–enol tautomerism, is one of the foundational concepts of organic chemistry, underlying everything from acid- and base-catalyzed reactions to the mechanisms of enzymes in living cells. The term appears almost exclusively in academic and laboratory contexts, and its derivatives — notably 'enolic' and 'enolate' — are staples of chemical literature. Though obscure to lay readers, the enol is indispensable to understanding how carbon-based molecules transform.
nounAn organic compound containing a hydroxyl group bonded to a carbon atom of a carbon–carbon double bond; the enediols are a special case where two such groups occur.
- An organic compound in which a hydroxyl group is attached to a carbon atom participating in a carbon–carbon double bond (the 'en' of alkene plus the 'ol' of alcohol).
"In acidic solution, the ketone rapidly equilibrates with its corresponding enol form."
"Simple enols such as vinyl alcohol exist only transiently before reverting to the more stable carbonyl form."
"The enzyme stabilizes the enol intermediate during the isomerization reaction."
Standard English plural, used when referring to multiple enol compounds.
"Most simple enols are too unstable to be isolated at room temperature."
Drop an 'ph' from phenol and you get an entire class of compounds — and one of organic chemistry's most famous balancing acts, the keto–enol shift.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of enol
The term 'enol' was introduced by German chemist Ludwig Knorr in the late nineteenth century as a portmanteau of 'ene' (from alkene) and 'ol' (the suffix for alcohols), reflecting the compound's dual character. It entered English-language chemistry shortly after its German coinage. The suffix '-ol' itself derives ultimately from 'alcohol,' a word of Arabic origin (al-kuḥl). Related coinages using the same building blocks include 'alkene,' 'diene,' and the '-ol' ending found in names such as phenol and ethanol.
Related word forms
How enol is actually used
A technical term confined to chemistry; almost never encountered outside scientific writing. In speech, chemists typically stress the first syllable.
Easily confused with enol
Phenol is a specific aromatic compound (C6H5OH), whereas enol denotes any compound bearing an –OH group attached directly to an alkene carbon.