Editing Ketone (section)

==Reactions==
===Keto-enol tautomerization===
{{main|Enol}}
[[Image:Keto enol tautomerism.svg|thumb|right|250px|Keto-enol tautomerism. '''1''' is the keto form; '''2''' is the enol.]]
Ketones that have at least one [[alpha-hydrogen]], undergo [[keto-enol tautomerization]]; the tautomer is an [[enol]]. Tautomerization is [[catalyzed]] by both acids and bases. Usually, the keto form is more stable than the enol. This equilibrium allows ketones to be prepared via the [[Hydration reaction|hydration]] of [[alkyne]]s.

===Acid/base properties of ketones===
{{chem2|C\sH}} bonds adjacent to the carbonyl in ketones are more acidic [[Acid dissociation constant|p''K''<sub>a</sub>]]&nbsp;≈&nbsp;20) than the {{chem2|C\sH}} bonds in alkane (p''K''<sub>a</sub>&nbsp;≈&nbsp;50). This difference reflects resonance stabilization of the [[enolate ion]] that is formed upon [[deprotonation]]. The relative acidity of the α-hydrogen is important in the enolization reactions of ketones and other carbonyl compounds. The acidity of the α-hydrogen also allows ketones and other carbonyl compounds to react as nucleophiles at that position, with either [[stoichiometric]] and catalytic base. Using very strong bases like lithium diisopropylamide (LDA, p''K''<sub>a</sub> of conjugate acid ~36) under non-equilibrating conditions (–78&nbsp;°C, 1.1 equiv LDA in THF, ketone added to base), the less-substituted ''kinetic'' ''enolate'' is generated selectively, while conditions that allow for equilibration (higher temperature, base added to ketone, using weak or insoluble bases, e.g., [[sodium ethoxide|{{chem2|CH3CH2ONa}}]] in [[ethanol|{{chem2|CH3CH2OH}}]], or [[sodium hydride|NaH]]) provides the more-substituted ''thermodynamic enolate''.

Ketones are also weak bases, undergoing [[protonation]] on the carbonyl oxygen in the presence of [[Brønsted acid]]s. Ketonium ions (i.e., protonated ketones) are strong acids, with p''K''<sub>a</sub> values estimated to be somewhere between –5 and –7.<ref>{{Cite web|url=http://evans.rc.fas.harvard.edu/pdf/evans_pKa_table.pdf|title=Evans pKa table|last=Evans|first=David A.|date=4 November 2005|website=Evans group website|access-date=14 June 2018|archive-date=19 June 2018|archive-url=https://web.archive.org/web/20180619071445/http://evans.rc.fas.harvard.edu/pdf/evans_pKa_table.pdf|url-status=dead}}</ref><ref>{{Cite book|title=March's Advanced Organic Chemistry|last=Smith|first=Michael B.|publisher=Wiley|year=2013|isbn=978-0-470-46259-1|edition=7th|location=Hoboken, N.J.|pages=314–315}}</ref> Although acids encountered in organic chemistry are seldom strong enough to fully protonate ketones, the formation of equilibrium concentrations of protonated ketones is nevertheless an important step in the mechanisms of many common organic reactions, like the formation of an acetal, for example. Acids as weak as pyridinium cation (as found in pyridinium tosylate) with a p''K''<sub>a</sub> of 5.2 are able to serve as catalysts in this context, despite the highly unfavorable equilibrium constant for protonation (''K''<sub>eq</sub>&nbsp;<&nbsp;10<sup>−10</sup>).

===Nucleophilic additions===
An important set of reactions follow from the susceptibility of the carbonyl carbon toward [[nucleophilic addition]] and the tendency for the enolates to add to electrophiles.
Nucleophilic additions include in approximate order of their generality:<ref name=March/>
* With water (hydration) gives [[geminal diol]]s, which are usually not formed in appreciable (or observable) amounts
* With an [[acetylide]] to give the α-[[hydroxyalkyne]]
* With [[ammonia]] or a [[primary amine]] gives an [[imine]]
* With [[secondary amine]] gives an [[enamine]]
* With [[Grignard reagent|Grignard]] and [[organolithium reagent]]s to give, after aqueous workup, a [[tertiary alcohol]]
* With an alcohols or [[alkoxide]]s to gives the [[hemiketal]] or its conjugate base. With a [[diol]] to the [[ketal]]. This reaction is employed to protect ketones.
* With [[sodium amide]] resulting in C–C bond cleavage with formation of the amide RCONH<sub>2</sub> and the alkane or arene R'H, a reaction called the Haller–Bauer reaction.<ref>[https://web.archive.org/web/20070910060716/http://nagoyaren.homeip.net/chem/reactions/123.htm Haller–Bauer Reaction]. homeip.net</ref>

===Oxidation===
[[File:Oxidation of Ketone.jpg|center|thumb|500px]]
Ketones are cleaved by strong oxidizing agents and at elevated temperatures. Their oxidation involves carbon–carbon bond cleavage to afford a mixture of carboxylic acids having lesser number of carbon atoms than the parent ketone. 

===Other reactions===
* [[Electrophilic addition]], reaction with an [[electrophile]] gives a resonance stabilized cation
* With [[phosphonium ylide]]s in the [[Wittig reaction]] to give the [[alkene]]s
* With [[thiol]]s to give the [[thioacetal]]
* With [[hydrazine]] or 1-disubstituted [[derivative (chemistry)|derivatives]] of hydrazine to give [[hydrazone]]s.
* With a [[metal hydride]] gives a metal alkoxide salt, hydrolysis of which gives the alcohol, an example of [[ketone reduction]]
* With [[halogen]]s to form an α-[[haloketone]], a reaction that proceeds via an [[enol]] (see [[Haloform reaction]])
* With [[heavy water]] to give an α-[[deuterated]] ketone
* Fragmentation in photochemical [[Norrish reaction]]
* Reaction of 1,4-aminodiketones to [[oxazoles]] by dehydration in the [[Robinson–Gabriel synthesis]]
* In the case of aryl–alkyl ketones, with sulfur and an amine give amides in the [[Willgerodt reaction]]
* With [[hydroxylamine]] to produce [[oxime]]s
* With [[reducing agents]] to form secondary alcohols
* With [[peroxy acid]]s to form [[ester]]s in the [[Baeyer–Villiger oxidation]]