P-chloranil

Chloranil is a quinone with the molecular formula C₆Cl₄O₂. Also known as tetrachloro-1,4-benzoquinone, it is a yellow solid. Like the parent benzoquinone, chloranil is a planar molecule J.-M. Lü, S. V. Rosokha, I. S. Neretin and J. K. Kochi, "Quinones as Electron Acceptors. X-Ray Structures, Spectral (EPR, UV-vis) Characteristics and Electron-Transfer Reactivities of Their Reduced Anion Radicals as Separated vs Contact Ion Pairs" Journal of the American Chemical Society 2006 128, 16708-16719. that functions as a mild oxidant.

Synthesis and use as reagent

Chloranil is produced by chlorination of phenol to give hexachlorocyclohexa-2,5-dien-1-one ("hexachlorophenol"). Hydrolysis of the dichloromethylene group in this dienone gives chloranil:
:C₆H₅OH + 6 Cl₂ → C₆Cl₆O + 6 HCl
:C₆Cl₆O + H₂O → C₆Cl₄O₂ + 2 HCl

Chloroanil serves as a hydrogen acceptor. It is more electrophilic than quinone itself. It is used for the aromatization reactions, such as the conversion of cyclohexadienes to the benzene derivatives.Derek R. Buckle "Chloranil" in ''Encyclopedia of Reagents for Organic Synthesis'', 2001, John Wiley.

Chloranil is used to test for free secondary amines. This test is useful for checking for the presence of proline derivatives. It is also a good test for the successful deprotection of a secondary amine. Secondary amines react with chloranil to give a brown/red/orange derivative, the colour depending on the amine. In these reactions, the amine displaces chloride from the ring of the quinone.

Commercial applications

It is a precursor to many dyes, such as pigment violet 23 and diaziquone (AZQ), a cancer chemotherapeutic agent.

See also

* Chloranilic acid
* 2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (DDQ)

References

External links

* {{PPDB, 1297

Organochlorides
Fungicides
1,4-Benzoquinones
Oxidizing agents