2,3-Dichloro-5,6-dicyano-1,4-benzoquinone

2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (or DDQ) is the chemical reagent with formula C6Cl2(CN)2O2. This oxidant is useful for the dehydrogenation of alcohols,[3] phenols,[4] and steroid ketones[5] in organic chemistry. DDQ decomposes in water, but is stable in aqueous mineral acid.[6]

"DDQ" redirects here. For the Australian television station, see RTQ.
2,3-Dichloro-5,6-dicyano-1,4-benzoquinone[1]
Structural formula of dichlorodicyanobenzoquinone
Space-filling model of the dichlorodicyanobenzoquinone molecule
Names
Preferred IUPAC name
4,5-Dichloro-3,6-dioxocyclohexa-1,4-diene-1,2-dicarbonitrile[2]
Other names
  • 2,3-Dichloro-5,6-dicyano-p-benzoquinone
  • 4,5-Dichloro-3,6-dioxo-1,4-cyclohexadiene-1,2-dicarbonitrile
  • Dichlorodicyanobenzoquinone
Identifiers
3D model (JSmol)
Abbreviations DDQ
ChemSpider
ECHA InfoCard 100.001.402
EC Number
  • 201-542-2
RTECS number
  • GU4825000
UNII
Properties
C8Cl2N2O2
Molar mass 227.00 g·mol−1
Appearance yellow to orange powder
Density 1.7g/cm3
Melting point 210 to 215 °C (410 to 419 °F; 483 to 488 K) (decomposes)
Boiling point 301.8 °C (575.2 °F; 575.0 K) at 760mmHg
reacts
Hazards
GHS pictograms
GHS Signal word Danger
GHS hazard statements
 H301
P264, P270, P301+310, P321, P330, P405, P501
Flash point 136.3 °C (277.3 °F; 409.4 K)
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

Preparation

Synthesis of DDQ involves cyanation of chloranil. Thiele and Günther first reported a 6-step preparation in 1906.[7] The substance did not receive interest until its potential as a dehydrogenation agent was discovered. A single-step chlorination from 2,3-dicyanohydroquinone was reported in 1965.[8]

Reactions

The reagent removes pairs of H atoms from organic molecules. The stoichiometry of its action is illustrated by the conversion of tetralin to naphthalene:

2 C6Cl2(CN)2O2 + C10H12 → 2 C6Cl2(CN)2(OH)2 + C10H8

The resulting hydroquinone is poorly soluble in typical reaction solvents (dioxane, benzene, alkanes), which facilitates workup.

Solutions of DDQ in benzene are red, due to the formation of a charge-transfer complex.[9]

Dehydrogenation

Aromatization
[10]

Cross-Dehydrogenative Coupling
[11]

Safety

DDQ reacts with water with release of hydrogen cyanide (HCN), which is highly toxic. A low-temperature and weakly acidic environment increases the stability of DDQ.

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References
  1. 2,3-Dichloro-5,6-dicyano-p-benzoquinone at Sigma-Aldrich
  2. Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book). Cambridge: The Royal Society of Chemistry. 2014. p. 50. doi:10.1039/9781849733069-FP001. ISBN 978-0-85404-182-4.
  3. Braude, E. A; Linstead, R. P.; Wooldridge, K. R. H. (1956). "593. Hydrogen Transfer. Part IX The Selective Dehydrogenation of Unsaturated Alcohols by High-potential Quinones". Journal of the Chemical Society (Resumed). 1956: 3070–3074. doi:10.1039/JR9560003070.
  4. Becker, H. D. (1965). "Quinone Dehydrogenation. I. Oxidation of Monohydric Phenols". Journal of Organic Chemistry. 30 (4): 982–989. doi:10.1021/jo01015a006.
  5. Turner, A. B.; Ringold, H. J. (1967). "Applications of High-potential Quinones. Part I. The Mechanism of Dehydrogenation of Steroidal Ketones by 2,3-Dichloro-5,6-Dicyanobenzoquinone". Journal of the Chemical Society C: Organic. 1967: 1720–1730. doi:10.1039/J39670001720.
  6. Derek R. Buckle, Steven J. Collier, Mark D. McLaws "2,3-Dichloro-5,6-dicyano-1,4-benzoquinone" in E-EROS ENCYCLOPEDIA OF REAGENTS FOR ORGANIC SYNTHESIS, 2005. doi:10.1002/047084289X.rd114.pub2
  7. Thiele, J.; Günther, F. (1906). "Ueber Abkömmlinge des Dicyanhydrochinons". Justus Liebig's Annalen der Chemie. 349 (1): 45–66. doi:10.1002/jlac.19063490103.
  8. Walker, D.; Waugh, T. D. (1965). "2,3-Dichloro-5,6-Dicyanobenzoquinone (DDQ). A New Preparation". The Journal of Organic Chemistry. 30 (9): 3240. doi:10.1021/jo01020a529.
  9. Rathore, Rajendra; Kochi, Jay K. (2000), "Donor/acceptor organizations and the electron-transfer paradigm for organic reactivity", Advances in Physical Organic Chemistry, Elsevier, pp. 193–318, doi:10.1016/s0065-3160(00)35014-6, ISBN 9780120335350
  10. Brown, W.; Turner, A. B. (1971). "Application of High-potential Quinones. 7. Synthesis of Steroidal Phenanthrenes by Double Methyl Migration". Journal of the Chemical Society C: Organic. 1971: 2566–2572. doi:10.1039/J39710002566. PMID 5167256.
  11. Zhang, Y.; Li, C. J. (2006). "DDQ-Mediated Direct Cross-Dehydrogenative-Coupling (CDC) between Benzyl Ethers and Simple Ketones". Journal of the American Chemical Society. 128 (13): 4242–4243. doi:10.1021/ja060050p. PMID 16568995.
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