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

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"DDQ" redirects here. DDQ is also the former callsign of a TV station in Toowoomba, Australia.
2,3-Dichloro-5,6-dicyano-1,4-benzoquinone[1]
Dichlorodicyanobenzoquinone.svg
Identifiers
Abbreviations DDQ
CAS number 84-58-2 YesY
PubChem 6775
ChemSpider 6517 YesY
EC number 201-542-2
RTECS number GU4825000
Jmol-3D images Image 1
Properties
Molecular formula 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
Solubility in water reacts
Hazards
R-phrases R25 R29
S-phrases S22 S24/25 S37 S45
Flash point 136.3 °C (277.3 °F; 409.4 K)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

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,[2] phenols,[3] and steroid ketones[4] in organic chemistry. DDQ decomposes in water, but is stable in aqueous mineral acid.[5]

Preparation[edit]

Synthesis of DDQ involves cyanation of chloranil. Thiele and Günther first reported a 6-step preparation in 1906.[6] 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.[7]

Reactions[edit]

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, alkanes), which facilitates workup.

Dehydrogenation[edit]

DDQ-dehydrogenation.png

Aromatization[edit]

DDQ-aromatization.png[8]

Oxidative coupling[edit]

DDQ-oxi-coupling1.png
[9]

Safety[edit]

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.

References[edit]

  1. ^ 2,3-Dichloro-5,6-dicyano-p-benzoquinone at Sigma-Aldrich
  2. ^ 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. 
  3. ^ Becker, H. D. (1965). "Quinone Dehydrogenation. I. Oxidation of Monohydric Phenols". Journal of Organic Chemistry 30 (4): 982–989. doi:10.1021/jo01015a006. 
  4. ^ 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. 
  5. ^ 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
  6. ^ Thiele, J.; Günther, F. (1906). "Ueber Abkömmlinge des Dicyanhydrochinons". Justus Liebig's Annalen der Chemie 349 (1): 45–66. doi:10.1002/jlac.19063490103. 
  7. ^ Walker, D.; Waugh, T. D. (1965). "2,3-Dichloro-5,6-Dicyanobenzoquinone (DDQ). A New Preparation". The Journal of Organic Chemistry 30 (9): 3240–3240. doi:10.1021/jo01020a529. 
  8. ^ 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. 
  9. ^ 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. 

External links[edit]