1,2-Dioxin

1,2-Dioxin
Names
	Preferred IUPAC name 1,2-Dioxine
	Systematic IUPAC name 1,2-Dioxacyclohexa-3,5-diene
Identifiers
CAS Number	289-87-2 ;
3D model (JSmol)	Interactive image;
ChemSpider	10606250 ;
PubChem CID	15559065;
UNII	R8H79L3J69 ;
CompTox Dashboard (EPA)	DTXSID90574144 ;
	InChI InChI=1S/C4H4O2/c1-2-4-6-5-3-1/h1-4H Key: VCZQYTJRWNRPHF-UHFFFAOYSA-N ; InChI=1/C4H4O2/c1-2-4-6-5-3-1/h1-4H Key: VCZQYTJRWNRPHF-UHFFFAOYAH;
	SMILES O1OC=CC=C1;
Properties
Chemical formula	C4H4O2
Molar mass	84.074 g·mol−1
Related compounds
Related compounds	Dibenzodioxin; 1,4-Dioxin
	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

1,2-Dioxin is a heterocyclic, organic, antiaromatic compound with the chemical formula C₄H₄O₂. It is an isomeric form of 1,4-dioxin (or p-dioxin).

Due to its peroxide-like characteristics, 1,2-dioxin is very unstable and has not been isolated. Calculations suggest that it would isomerize rapidly into but-2-enedial. Even substituted derivatives, such as 1,4-diphenyl-2,3-benzodioxin, are very labile.

In 1990, 3,6-bis(p-tolyl)-1,2-dioxin (1) was incorrectly reported as the first stable derivative. It was subsequently shown that the initial compound was not a derivative of 1,2-dioxin, but a thermodynamically more stable dione (2).