1,2-Dioxin

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| Verifiedfields = changed

| Watchedfields = changed

| verifiedrevid = 477204382

| ImageFile = 1,2-dioxin.svg

| ImageSize = 100

| ImageName = Skeletal formula of 1,2-dioxin

| ImageFileL1 = 1,2-Dioxin-3D-balls 2.png

| ImageFileR1 = 1,2-Dioxin-3D-spacefill.png

| ImageName1 = Ball and stick model of 1,2-dioxin

| PIN= 1,2-Dioxine

| SystematicName = 1,2-Dioxacyclohexa-3,5-diene

|Section1={{Chembox Identifiers

| CASNo_Ref = {{cascite|changed|??}}

| CASNo = 289-87-2

| UNII_Ref = {{fdacite|correct|FDA}}

| UNII = R8H79L3J69

| PubChem = 15559065

| ChemSpiderID = 10606250

| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}

| SMILES = O1OC=CC=C1

| StdInChI = 1S/C4H4O2/c1-2-4-6-5-3-1/h1-4H

| StdInChI_Ref = {{stdinchicite|correct|chemspider}}

| InChI = 1/C4H4O2/c1-2-4-6-5-3-1/h1-4H

| StdInChIKey = VCZQYTJRWNRPHF-UHFFFAOYSA-N

| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}

| InChIKey = VCZQYTJRWNRPHF-UHFFFAOYAH

}}

|Section2={{Chembox Properties

| C=4 | H=4 | O=2

}}

|Section3={{Chembox Related

| OtherCompounds = Dibenzodioxin

1,4-Dioxin

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{{For|other dioxin compounds|dioxin}}

1,2-Dioxin is a heterocyclic, organic, antiaromatic{{Cite journal |last1=Pelloni |first1=Stefano |last2=Faglioni |first2=Francesco |last3=Lazzeretti |first3=Paolo |date=2013-09-01 |title=Parity violation energies of C4H4X2 molecules for X = O, S, Se, Te and Po |url=https://doi.org/10.1080/00268976.2013.794396 |journal=Molecular Physics |volume=111 |issue=16–17 |pages=2387–2391 |doi=10.1080/00268976.2013.794396 |s2cid=100861633 |issn=0026-8976|url-access=subscription |hdl=11380/942493 |hdl-access=free }} compound with the chemical formula C{{sub|4}}H{{sub|4}}O{{sub|2}}. It is an isomeric form of 1,4-dioxin (or p-dioxin).

:File:Dioxin isomers.svg{{clear-left}}

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.{{Cite book|last=Matsumoto|first=M.|chapter-url=https://books.google.com/books?id=Ah6GAwAAQBAJ&pg=PA13|title=Science of Synthesis: Houben-Weyl Methods of Molecular Transformations Vol. 16: Six-Membered Hetarenes with Two Identical Heteroatoms|publisher=Georg Thieme Verlag|year=2014|isbn=9783131718815|pages=13|chapter=Product Class 1: 1,2-Dioxins and Benzo- and Dibenzo- Fused Derivatives|access-date=2020-06-12}} Even substituted derivatives, such as 1,4-diphenyl-2,3-benzodioxin, are very labile.{{Cite journal | doi = 10.1021/ja00368a021| title = Chemiluminescence of organic peroxides. Thermal generation of an o-xylylene peroxide| journal = Journal of the American Chemical Society| volume = 104| issue = 4| pages = 1041| year = 1982| last1 = Smith| first1 = Jimmie P.| last2 = Schrock| first2 = Alan K.| last3 = Schuster| first3 = Gary B.}}.

:File:1,4-diphenyl-2,3-benzodioxin.svg{{clear-left}}

In 1990, 3,6-bis(p-tolyl)-1,2-dioxin (1) was incorrectly reported as the first stable derivative.{{Cite journal | doi = 10.1021/jo00300a026| title = Electron transfer to excited doublet states. Photoirradiation of 10-methylphenothiazine cation radical perchlorate in solutions of phenylacetylene and p-tolylacetylene in acetonitrile| journal = The Journal of Organic Chemistry| volume = 55| issue = 13| pages = 4086| year = 1990| last1 = Shine| first1 = Henry J.| last2 = Zhao| first2 = Da Chuan}}. It was subsequently shown that the initial compound was not a derivative of 1,2-dioxin, but a thermodynamically more stable dione (2).{{Cite journal | doi = 10.1021/jo034305i| pmid = 12737603| title = Revised Structure of a Purported 1,2-Dioxin: A Combined Experimental and Theoretical Study| journal = The Journal of Organic Chemistry| volume = 68| issue = 10| pages = 4108–11| year = 2003| last1 = Block| first1 = Eric| last2 = Shan| first2 = Zhixing| last3 = Glass| first3 = Richard S.| last4 = Fabian| first4 = Jürgen}}

:File:Revised structure 1,2-Dioxin.svg{{clear-left}}