Diketene

Diketene
Names
	Preferred IUPAC name 4-Methylideneoxetan-2-one
	Other names γ-Methylenepropiolactone
Identifiers
CAS Number	674-82-8 ;
3D model (JSmol)	Interactive image;
ChemSpider	12140 ;
ECHA InfoCard	100.010.562
EC Number	211-617-1;
PubChem CID	12661;
RTECS number	RQ8225000;
UNII	0DZ97C3Z7D;
UN number	2521
CompTox Dashboard (EPA)	DTXSID9027289 ;
	InChI InChI=1S/C4H4O2/c1-3-2-4(5)6-3/h1-2H2 Key: WASQWSOJHCZDFK-UHFFFAOYSA-N ; InChI=1/C4H4O2/c1-3-2-4(5)6-3/h1-2H2 Key: WASQWSOJHCZDFK-UHFFFAOYAM;
	SMILES O=C1OC(=C)C1;
Properties
Chemical formula	C4H4O2
Molar mass	84.074 g·mol−1
Density	1.09 g cm−3
Melting point	−7 °C (19 °F; 266 K)
Boiling point	127 °C (261 °F; 400 K)
Viscosity	0.88 mPa.s
Hazards
	GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H226, H301, H302, H315, H318, H330, H331, H332, H335
Precautionary statements	P210, P233, P240, P241, P242, P243, P260, P261, P264, P270, P271, P280, P284, P301+P310, P301+P312, P302+P352, P303+P361+P353, P304+P312, P304+P340, P305+P351+P338, P310, P311, P312, P320, P321, P330, P332+P313, P362, P370+P378, P403+P233, P403+P235, P405, P501
Flash point	33 °C (91 °F; 306 K)
Autoignition; temperature	275
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

Diketene is an organic compound with the molecular formula C₄H₄O₂, and which is sometimes written as (CH₂CO)₂. It is formed by dimerization of ketene, H₂C=C=O. Diketene is a member of the oxetane family. It is used as a reagent in organic chemistry. It is a colorless liquid.