Quinone

A quinone is a class of organic compounds that are formally "derived from aromatic compounds by conversion of an even number of –CH= groups into –C(=O)– groups with any necessary rearrangement of double bonds," resulting in "a fully conjugated cyclic dione structure." The class includes some heterocyclic compounds.

The prototypical member of the class are 1,4-benzoquinone or cyclohexadienedione, often called simply quinone (whence the name of the class). Other important examples are 1,2-benzoquinone (ortho-quinone), 1,4-naphthoquinone and 9,10-anthraquinone.

Quinones are oxidized derivatives of aromatic compounds and are often readily made from reactive aromatic compounds with electron-donating substituents such as phenols and catechols, which increase the nucleophilicity of the ring and contributes to the large redox potential needed to break aromaticity. (Quinones are conjugated but not aromatic). Quinones are electrophilic Michael acceptors stabilised by conjugation. Depending on the quinone and the site of reduction, reduction can either rearomatise the compound or break the conjugation. Conjugate addition nearly always breaks the conjugation.

• 1,2-Benzoquinone

• 1,4-Benzoquinone

• 1,4-Naphthoquinone

• 9,10-Anthraquinone

The term quinone is also used more generally for a large class of compounds formally derived from aromatic quinones through replacement of some hydrogen atoms by other atoms or radicals.

• Chloranil

• Lawsone

• DDQ