1,2-Benzoquinone

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 ethyl 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]

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
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
Density 1.424 g/cm3
Melting point 60–70 °C (140–158 °F; 333–343 K) decomposes[2]
Hazards
Flash point 76.4 °C (169.5 °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 °C [77 °F], 100 kPa).
☒N verify (what is checkY☒N ?)
Infobox references

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
  1. Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book). Cambridge: The Royal Society of Chemistry. 2014. p. 728. doi:10.1039/9781849733069-FP001. ISBN 978-0-85404-182-4.
  2. Eagleson, Mary (1994). Concise encyclopedia chemistry. Berlin: Walter de Gruyter. p. 123. ISBN 0-89925-457-8. OCLC 29029713.
  3. Patai, Saul, ed. (1974). Quinonoid Compounds: Vol. 1 (1974). PATAI'S Chemistry of Functional Groups. doi:10.1002/9780470771297. ISBN 9780470771297.
  4. Patai, Saul, ed. (1974). Quinonoid Compounds: Vol. 2 (1974). PATAI'S Chemistry of Functional Groups. doi:10.1002/9780470771303. ISBN 9780470771303.
  5. MacDonald, Alistair L.; Trotter, James (1973). "Crystal and molecular structure of o-benzoquinone". Journal of the Chemical Society, Perkin Transactions 2 (4): 476. doi:10.1039/P29730000476.
  6. Magdziak, D.; Rodriguez, A. A.; Van De Water, R. W.; Pettus, T. R. R. (2002). "Regioselective oxidation of phenols to o-quinones with o-iodoxybenzoic acid (IBX)". Org. Lett. 4 (2): 285–288. doi:10.1021/ol017068j. PMC 1557836. PMID 11796071.
  7. Chanda Parulekar and Suneela Mavinkurve (2006). "Formation of ortho-benzoquinone from sodium benzoate by Pseudomonas mendocina P2d" (PDF). Indian Journal of Experimental Biology. 44 (2): 157–162. PMID 16480184.
  8. Liao, Chun-Chen; Peddinti, Rama Krishna (2002). "Masked o-Benzoquinones in Organic Synthesis". Accounts of Chemical Research. 35 (10): 856–866. doi:10.1021/ar000194n. PMID 12379138.
  9. Teuber HJ (1972). "Use of Dipotassium Nitrosodisulfonate (Frémy's Salt): 4,5-Dimethyl-o-Benzoquinone". Org. Synth. 52: 88. doi:10.15227/orgsyn.052.0088.
  10. Mure, Minae; Wang, Sophie X.; Klinman, Judith P. (2003). "Synthesis and Characterization of Model Compounds of the Lysine Tyrosyl Quinone Cofactor of Lysyl Oxidase". Journal of the American Chemical Society. 125 (20): 6113–6125. doi:10.1021/ja0214274. PMID 12785842.
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