When ''keto-enol tautomerism'' occurs the keto or enol is deprotonated and an anion, which is called the enolate, is formed as [[reaction intermediate|intermediate]]. Enolates can exist in quantitative amounts in strictly [[Brønsted acid]] free conditions, since they are generally very basic. In enolates the anionic charge is delocalized over the oxygen and the carbon
.<ref>{{GoldBookRef|Nic, fileM.; =Jirat, E02123J.; |Kosata, titleB., =eds. (2006–). "enolates}}". IUPAC Compendium of Chemical Terminology (Online ed.). doi:10.1351/goldbook.E02123. ISBN 0-9678550-9-8. [http://goldbook.iupac.org/E02123.html Enolates].</ref> Enolates are somewhat stabilized by this delocalization of the charge over three atoms.<ref>[http://pharmaxchange.info/press/2011/02/chemistry-of-enolates-and-enols-acidity-of-alpha-hydrogens/ Chemistry of Enolates and Enols - Acidity of alpha-hydrogens]</ref> In older descriptions of bonding, particularly [[valence bond theory]] this was explained by a phenomenon known as [[Resonance (chemistry)|resonance]].
