An enone is an unsaturated chemical compound or functional group consisting of a conjugated system of an alkene and a ketone. The simplest enone is methyl vinyl ketone (MVK) or CH2=CHCOCH3.
As an example, an enone such as a chalcone can be synthesized in a Knoevenagel condensation. In the Meyer–Schuster rearrangement the starting compound is a propargyl alcohol.
Enones undergo reactions vinylogous to the corresponding saturated carbonyl compounds, i.e. conjugate additions. They are electrophilic also at the β-carbon, which can be attacked by nucleophiles. Both direct addition to carbonyl and conjugate addition may occur, depending on conditions. The attack on the carbon produces a more stable compound than direct attack. An example of this is the toxicity, which follows from their ability to alkylate DNA. When the nucleophile is an hydride the reaction is called conjugate reduction.
An enone is a reactant in the Nazarov cyclization reaction and in the Rauhut–Currier reaction (dimerization).
Enone is not to be confused with Ketene (R2C=C=O). An enamine is a cousin of an enone, with the carbonyl replaced by an amine group. An enal is the corresponding α,β-unsaturated aldehyde.