Ketones engage in many organic reactions. The most important 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:
* With water (hydration) gives geminal diols, 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 and organolithium reagents to give, after aqueous workup, a tertiary alcohol
* With an alcohols or alkoxides 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 and the alkane or arene R'H, a reaction called the Haller–Bauer reaction.
* With strong oxidizing agents to give carboxylic acids. Ketones are generally oxidized under vigorous conditions, i.e., 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. 
* Electrophilic addition, reaction with an electrophile gives a resonance stabilized cation
* With phosphonium ylides in the Wittig reaction to give the alkenes
* With thiols to give the thioacetal
* With hydrazine or 1-disubstituted derivatives of hydrazine to give hydrazones.
* With a metal hydride gives a metal alkoxide salt, hydrolysis of which gives the alcohol, an example of ketone reduction
* With halogens 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 oximes
* With reducing agents to form secondary alcohols
* With peroxy acids to form esters in the Baeyer–Villiger oxidation