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1,4-Benzoquinone

1,4-Benzoquinone is the chemical compound with the formula C₆H₄O₂. In pure state, it forms bright yellow crystals with characteristic irritating odor, resembling that of chlorine; impure samples are often dark colored due to the presence of quinhydrone (1:1 complex of quinone with hydroquinone). This nonaromatic six-membered ring compound is the oxidized derivative of 1,4-hydroquinone.^[1] The molecule is multifunctional: it exhibits properties of a ketone, forming an oxime; an oxidant, forming the dihydroxy derivative; and an alkene, undergoing addition reactions, especially those typical for α,β-unsaturated ketones. 1,4-Benzoquinone is sensitive towards both strong mineral acids and alkalies, which cause condensation and decomposition of the compound.

Applications in organic synthesis

It is used as a hydrogen acceptor and oxidant in organic synthesis.^[2] 1,4-Benzoquinone serves as a dehydrogenation reagent. It is also uses as a dienophile in Diels Alder reactions.^[3]

Benzoquinone reacts with acetic anhydride and sulfuric acid to the triacetate of 1,3,4-trihydroxybenzene. This reaction is called the Thiele reaction ^[4] after Johannes Thiele who first described the reaction in 1898. An application is found in total synthesis ^[5]:

Related 1,4-benzoquinones

A variety of derivatives and analogues are known. Illustrative examples:

• 1,4-Naphthoquinone, derived by oxidation of naphthalene with chromium trioxide.^[6]
• 2,3-dichloro-5,6-dicyano-1,4-benzoquinone, a stronger oxidant and dehydrogenation agent than 1,4-benzoquinone.^[7]
• Ubiquinone-1, a naturally occurring 1,4-benzoquinone.
• Chloro-p-benzoquinone, (CAS no. [695-99-8])^[8]
• Chloranil, 1,4-C₆Cl₄O₂, a stronger oxidant and dehydrogenation agent than 1,4-benzoquinone.

See also

• 1,2-Benzoquinone
• Quinones

References

1. ^ H. W. Underwood, Jr. and W. L. Walsh (1943). "Quinone". Org. Synth.; Coll. Vol. 2: 553. 
2. ^ Yang, T.-K.; Shen, C.-Y. ”1,4-Benzoquinone” in Encyclopedia of Reagents for Organic Synthesis (Ed: L. Paquette) 2004, J. Wiley & Sons, New York. doi:10.1002/047084289.
3. ^ Oda, M.; Kawase, T.; Okada, T.; Enomoto, T. (1998). "2-Cyclohexene-1,4-dione". Org. Synth.; Coll. Vol. 9: 186. 
4. ^ Ueber die Einwirkung von Essigsäure-anhydrid auf Chinon und auf Dibenzoylstyrol (p 1247-1249) Johannes Thiele Berichte der deutschen chemischen Gesellschaft Volume 31, Issue 1 , Pages 1247 - 1249 1898 doi:10.1002/cber.189803101226
5. ^ Stereoselective Total Synthesis and Enantioselective Formal Synthesis of the Antineoplastic Sesquiterpene Quinone Metachromin A Wanda P. Almeida, and Carlos Roque D. Correia J. Braz. Chem. Soc., Vol. 10, No. 5, 401-414, 1999 doi:10.1590/S0103-50531999000500011.
6. ^ E. A. Braude E. A.; Fawcett, J. S. (1963). "1,4-Naphthoquinone". Org. Synth.; Coll. Vol. 4: 698. 
7. ^ Vogel, E.; Klug, W.; Breuer, A. (1988). "1,6-Methano[10]annulene". Org. Synth.; Coll. Vol. 6: 731. 
8. ^ Harman, R. E. (1963). "Chloro-p-benzoquinone". Org. Synth.; Coll. Vol. 4: 148.