2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (or DDQ) is the
chemical reagent
In chemistry, a reagent ( ) or analytical reagent is a substance or compound added to a system to cause a chemical reaction, or test if one occurs. The terms ''reactant'' and ''reagent'' are often used interchangeably, but reactant specifies a ...
with formula C
6Cl
2(CN)
2O
2. This oxidant is useful for the dehydrogenation of alcohols,
phenols, and steroid ketones. DDQ decomposes in water, but is stable in aqueous
mineral acid
A mineral acid (or inorganic acid) is an acid derived from one or more inorganic compounds, as opposed to organic acids which are acidic, organic compounds. All mineral acids form hydrogen ions and the conjugate base when dissolved in water.
Cha ...
.
Preparation
Synthesis of DDQ involves
cyanation of
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, "Qui ...
.
J. Thiele and F. Günther first reported a 6-step preparation in 1906. 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.
Reactions
The reagent removes pairs of H atoms from organic molecules. The stoichiometry of its action is illustrated by the conversion of
tetralin
Tetralin (1,2,3,4-tetrahydronaphthalene) is a hydrocarbon having the chemical formula C10H12. It is a partially hydrogenated derivative of naphthalene. It is a colorless liquid that is used as a hydrogen-donor solvent.
Production
Tetralin is pro ...
to
naphthalene:
:2 C
6Cl
2(CN)
2O
2 + C
10H
12 → 2 C
6Cl
2(CN)
2(OH)
2 + C
10H
8
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.
Dehydrogenation
:
Aromatization
:
Cross-Dehydrogenative Coupling
:
:
Safety
DDQ reacts with water to release highly toxic
hydrogen cyanide (HCN). A low-temperature and weakly acidic environment increases the stability of DDQ.
References
External links
"Like Neurons in the Brain": A Molecular Computer that Evolves
{{DEFAULTSORT:Dichloro-5, 6-Dicyano-1, 4-Benzoquinone, 2, 3-
Nitriles
Organochlorides
1,4-Benzoquinones
Oxidizing agents
Reagents for organic chemistry