Quinone
Encyclopedia : Q : QU : QUI : Quinone
A quinone (or benzoquinone) is either one of the two isomers of cyclohexadienedione or a derivative thereof. Quinones are not aromatic, but are dienes. The carbonyl groups are ketone-like. Benzoquinone exists in either of two isomers with the chemical formula C6H4O2. Ortho-benzoquinone' is the 1,2-dione, whereas para-quinone, or parabenzoquinone, is the 1,4-dione. Parabenzoquinone is the oxidized form of hydroquinone, and ortho-benzoquinone is the oxidized form of catechol (1,2-dihydroxybenzene). For example, an acidic Potassium iodide solution reduces a solution of benzoquinone to hydroquinone, which is oxidized back with a solution of silver nitrate.
 orthobenzoquinone |
 parabenzoquinone |
The word quinone refers to the entire class of cyclohexadienediones.
Biochemistry
Quinone is a common constituent of biologically relevant molecules (e.g. Vitamin K1 is phylloquinone) that serve as electron acceptors in electron transport chains such as those in Photosystems I & II of photosynthesis, and aerobic respiration. Quinones are oxidizing agents and because of this it is used in the spray of bombardier beetles. Hydroquinone is reacted with hydrogen peroxide to produce a fiery blast of steam, a strong deterent in the animal world.Organic chemistry
Benzoquinone is used in organic chemistry as an oxidizing agent. Even stronger agents exist such as 2,3,5,6-tetrachloro-parabenzoquinone or p-chloranil and 2,3-dicyano-5,6-dichloro-parabenzoquinone or DDQ for short [link].See also
External links
- Redox system Benzoquinone / Hydroquinone [Website]
- For a full list of external links to MSDSs, spectroscopic data, commercial chemicals suppliers etc. for this compound, see [Chemical sources].
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