Chloranil

Chloranil[1]
Names
IUPAC name
2,3,5,6-Tetrachlorocyclohexa-2,5-diene-1,4-dione
Other names
p-Chloranil; Tetrachloro-1,4-benzoquinone; Tetrachloro-p-benzoquinone
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.003.887
KEGG
UNII
Properties
C6Cl4O2
Molar mass 245.86 g·mol−1
Appearance Yellow solid
Melting point 295 to 296 °C (563 to 565 °F; 568 to 569 K)
-112.6·10−6 cm3/mol
Hazards
R-phrases (outdated) R36/38 R50/53
S-phrases (outdated) S37 S60 S61
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

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[2] 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:[3]

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.[4]

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

References

  1. ↑ Chloranil at Sigma-Aldrich
  2. ↑ 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.doi:10.1021/ja066471o
  3. ↑ François Muller and Liliane Caillard "Chlorophenols" in Ullmann's Encyclopedia of Industrial Chemistry Wiley-VCH, Weinheim, 2011. doi:10.1002/14356007.a07_001.pub2
  4. ↑ Derek R. Buckle "Chloranil" in Encyclopedia of Reagents for Organic Synthesis, 2001, John Wiley. doi:10.1002/047084289X.rc057
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