Cyclobutadiene

Cyclobutadiene is an organic compound with the formula C₄H₄. It is very reactive owing to its tendency to dimerize. Although the parent compound has not been isolated, some substituted derivatives are robust and a single molecule of cyclobutadiene is quite stable. Since the compound degrades by a bimolecular process, the species can be observed by matrix isolation techniques at temperatures below 35 K. It is thought to adopt a rectangular structure.[1][2]

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Cyclobutadiene

Names
Preferred IUPAC name Cyclobuta-1,3-diene
Other names 1,3-Cyclobutadiene Cyclobutadiene [4]Annulene
Identifiers
CAS Number	1120-53-2 Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:33657 Y
ChemSpider	120626 Y
PubChem CID	136879
UNII	I5G5583N4F Y
CompTox Dashboard (EPA)	DTXSID00149807
InChI InChI=1S/C4H4/c1-2-4-3-1/h1-4H Y Key: HWEQKSVYKBUIIK-UHFFFAOYSA-N Y InChI=1/C4H4/c1-2-4-3-1/h1-4H Key: HWEQKSVYKBUIIK-UHFFFAOYAI
SMILES C1=CC=C1
Properties
Chemical formula	C4H4
Molar mass	52.076 g·mol−1
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