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

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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] DDQ decomposes in water, but is stable in aqueous mineral acid.[6]

Quick Facts Names, Identifiers ...
2,3-Dichloro-5,6-dicyano-1,4-benzoquinone[1]
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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
  • InChI=1S/C8Cl2N2O2/c9-5-6(10)8(14)4(2-12)3(1-11)7(5)13 Y
    Key: HZNVUJQVZSTENZ-UHFFFAOYSA-N Y
  • InChI=1/C8Cl2N2O2/c9-5-6(10)8(14)4(2-12)3(1-11)7(5)13
    Key: HZNVUJQVZSTENZ-UHFFFAOYAL
  • ClC=1C(=O)C(\C#N)=C(\C#N)C(=O)C=1Cl
Properties
C8Cl2N2O2
Molar mass 227.00 g·mol−1
Appearance yellow to orange powder
Density 1.7g/cm3
Melting point 210–215 °C (410–419 °F; 483–488 K) (decomposes)
Boiling point 301.8 °C (575.2 °F; 575.0 K) at 760mmHg
reacts
Hazards
GHS labelling:
GHS06: Toxic
Danger
H301
P264, P270, P301+P310, 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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Preparation

Synthesis of DDQ involves cyanation of chloranil. J. Thiele and F. 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

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Aromatization

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Cross-Dehydrogenative Coupling

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[11]

Safety

DDQ reacts with water to release highly toxic hydrogen cyanide (HCN).[6]

References

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