1,2-Benzoquinone

Chemical compound From Wikipedia, the free encyclopedia

1,2-Benzoquinone, also called ortho-benzoquinone, is an organic compound with formula C6H4O2. It is one of the two isomers of quinone, the other being 1,4-benzoquinone. It is a red volatile solid that is soluble in water and diethyl ether. It is rarely encountered because of its instability, but it is of fundamental interest as the parent compound of many derivatives which are known.[3][4]

Quick facts Names, Identifiers ...
1,2-Benzoquinone
Names
Preferred IUPAC name
Cyclohexa-3,5-diene-1,2-dione[1]
Other names
  • ortho-Benzoquinone
  • o-Benzoquinone
  • o-Quinone
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.243.463 Edit this at Wikidata
KEGG
UNII
  • InChI=1S/C6H4O2/c7-5-3-1-2-4-6(5)8/h1-4H checkY
    Key: WOAHJDHKFWSLKE-UHFFFAOYSA-N checkY
  • InChI=1/C6H4O2/c7-5-3-1-2-4-6(5)8/h1-4H
    Key: WOAHJDHKFWSLKE-UHFFFAOYAR
  • O=C1/C=C\C=C/C1=O
  • C1=CC(=O)C(=O)C=C1
Properties
C6H4O2
Molar mass 108.096 g·mol−1
Appearance Red volatile solid
Density 1.424 g/cm3
Melting point 60–70 Â°C (140–158 Â°F; 333–343 K) decomposes[2]
Hazards
Flash point 76.4 Â°C (169.5 Â°F; 349.5 K)
Related compounds
Related compounds
 1,4-benzoquinone
quinone
Except where otherwise noted, data are given for materials in their standard state (at 25 Â°C [77 Â°F], 100 kPa).
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Structure

The molecule has C2v symmetry. X-ray crystallography shows that the double bonds are localized, with alternatingly long and short C-C distances within the ring. The C=O distances of 1.21 Å are characteristic of ketones.[5]

Preparation and reactions

1,2-Benzoquinone is produced on oxidation of catechol exposed to air in aqueous solution[6] or by ortho oxidation of a phenol.[6]

A strain of the bacterium Pseudomonas mendocina metabolises benzoic acid, yielding 1,2-benzoquinone via catechol.[7]

Ortho-quinones are widely used in organic synthesis.[8]

Occurrence of ortho-quinones

The oxidation of lysyl side chains is effected in nature by the action of an orthoquinone called lysyl tyrosylquinone.

4,5-Dimethyl-1,2-benzoquinone, also a red solid, is a well behaved synthetic ortho-quinone.[9]

The biological pigment melanin is rich in ortho-quinones.

Finally, the enzyme cofactors tryptophan tryptophylquinone (TTQ), cysteine tryptophylquinone (CTQ), lysine tyrosylquinone (LTQ) and pyrroloquinoline quinone (PQQ) contain the ortho-quinone moiety in their chemical structure.[10]

See also

References

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