Methyl vinyl ketone^[1]

Names
Preferred IUPAC name But-3-en-2-one
Other names MVK Methylene acetone
Identifiers
CAS Number	78-94-4 Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:48058 Y
ChemSpider	6322 Y
ECHA InfoCard	100.001.055
PubChem CID	6570
UNII	AR7642I1MP Y
CompTox Dashboard (EPA)	DTXSID3025671
InChI InChI=1S/C4H6O/c1-3-4(2)5/h3H,1H2,2H3 Y Key: FUSUHKVFWTUUBE-UHFFFAOYSA-N Y InChI=1/C4H6O/c1-3-4(2)5/h3H,1H2,2H3 Key: FUSUHKVFWTUUBE-UHFFFAOYAV
SMILES CC(=O)C=C
Properties
Chemical formula	C4H6O
Molar mass	70.09 g/mol
Density	0.8407 g/cm3
Melting point	−7 °C (19 °F; 266 K)
Boiling point	81.4 °C (178.5 °F; 354.5 K)
Hazards
GHS labelling:
Pictograms
Signal word	Danger
NFPA 704 (fire diamond)	4 3 2
Flash point	−7 °C (19 °F; 266 K)
Autoignition temperature	370 °C (698 °F; 643 K)
Explosive limits	2.1% v/v (lower), 15.6% v/v (higher)
Safety data sheet (SDS)	Fisher Scientific
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is YN ?) Infobox references

Methyl vinyl ketone (MVK, IUPAC name: butenone) is the organic compound with the formula CH₃C(O)CH=CH₂. It is a reactive compound classified as an enone, in fact the simplest example thereof. It is a colorless, flammable, highly toxic liquid with a pungent odor. It is soluble in water and polar organic solvents. It is a useful intermediate in the synthesis of other compounds.^[2]

MVK has been prepared industrially by the condensation of acetone and formaldehyde, followed by dehydration. Similarly it is prepared by the Mannich reaction involving diethylammonium chloride and acetone, which produces the Mannich adduct:^[2][3]

CH₃C(O)CH₃ + CH₂O + [H₂NEt₂]Cl → [CH₃C(O)CH₂CH₂N(H)Et₂]Cl + H₂O

Heating this ammonium salt releases the ammonium chloride and the MVK:^[3]

[CH₃C(O)CH₂CH₂N(H)Et₂]Cl → CH₃C(O)CH=CH₂ + [H₂NEt₂]Cl

MVK can act as an alkylating agent because it is an effective Michael acceptor. It gained early attention for its use in the Robinson annulation, a method useful in the preparation of steroids:

Its alkylating ability is both the source of its high toxicity and the feature that makes it a useful intermediate in organic synthesis. MVK will polymerize spontaneously. The compound is typically stored with hydroquinone, which inhibits polymerization.

As an electrophilic alkene, it forms an adduct with cyclopentadiene. The resulting norbornene derivative is an intermediate in the synthesis of the anticholinergic drug biperiden. Via its cyanohydrin is also a precursor to vinclozolin. It is also a precursor to synthetic vitamin A.^[2]

MVK is an intermediate in the synthesis of some pharmaceutical drugs including etorphine, buprenorphine, tolquinzole, butaclamol, and etretinate.^{[citation needed]}

MVK is used in the synthesis of Wieland–Miescher ketone.

MVK is extremely hazardous upon inhalation causing coughing, wheezing and shortness of breath even at low concentrations. It will also readily cause irritation of the skin, eyes, and mucous membranes.

• NJ Hazardous Substance Factsheet for methyl vinyl ketone
• MSDS for methyl vinyl ketone Archived 2006-10-15 at the Wayback Machine
• Compilation of Henry's law constants for inorganic and organic species of potential importance in environmental chemistry. Sander, R. 1999-04-08.