quinone
American Heritage Dictionary:
Top
qui·none
(kwĭ-nōn', kwĭn'ōn') 
n.
Any of a class of aromatic compounds found widely in plants, especially the yellow crystalline form, C6H4O2, used in making dyes, tanning hides, and photography.
n.
Any of a class of aromatic compounds found widely in plants, especially the yellow crystalline form, C6H4O2, used in making dyes, tanning hides, and photography.
Britannica Concise Encyclopedia:
Top
quinone
Any member of a class of cyclic organic compounds comprising a six-membered unsaturated ring ( saturation) to which two oxygen atoms are bonded as carbonyl groups (CO; functional group). This structure plays an important role in theories of chemical structure and colour, since quinones occur as pigments in bacteria, fungi, and certain higher plants; animals containing quinones obtain them from plants they eat. The K vitamins ( vitamin K) are naphthoquinones. The term quinone often specifically denotes -benzoquinone (C6H4O2), a bright yellow solid with a sharp odour used in manufacturing dyes and fungicides and in photography.
For more information on quinone, visit Britannica.com.
Top
One of a class of aromatic diketones in which the carbon atoms of the carbonyl groups are part of the ring structure. The name quinone is applied to the whole group, but it is often used specifically to refer to p-benzoquinone (1), o-Benzoquinone (2) is also known but the meta isomer does not exist. 1
Quinones are prepared by oxidation of the corresponding aromatic ring systems containing amino (NH2) or hydroxyl (OH) groups on one or both of the carbon atoms being converted to the carbonyl group.
Three of the several possible quinones derived from naphthalene are known: 1,4-naphthoquinone (3), 1,2-naphthoquinone, and 2,6-naphthoquinone (4). 3
Important naturally occurring naphthoquinones are vitamins K1 and K2 which are found in blood and are responsible for proper blood clotting reaction. A number of quinone pigments have been isolated from plants and animals. Illustrative of these are juglone found in unripe walnut shells and spinulosin from the mold Penicillium spinuhsum. 9,10-Anthraquinone derivatives form an important class of dyes of which alizarin is the parent type. p-Benzoquinone is manufactured for use as a photographic developer. See also Aromatic hydrocarbon; Dye; Ketone.
Word Tutor:
Top
benzoquinone
IN BRIEF: n. - Any of a class of aromatic yellow compounds including several that are biologically important as coenzymes or acceptors or vitamins.
LearnThatWord.com is a free vocabulary and spelling program where you only pay for results!
Top
- a common name for p-benzoquinone.
- any member of a class of diketones derivable from aromatic compounds by conversion of two CH groups into CO groups with any necessary rearrangement of double bonds. Simple quinones are usually p-quinones, i.e. derivatives of p-benzoquinone (compare hydroquinone (def. 2)), but they may also be o-quinones, i.e. derivatives of o-benzoquinone (compare catechol (def. 2)). Naturally occurring quinones form a large, varied, and widespread group of compounds; they include numerous pigments, various electron carriers (e.g. plastoquinone, ubiquinone), and vitamins K. See also semiquinone.
| quinolinic acid, quinol, quinoid | |
| quinonoid, quinoprotein, quinovosamine |
Wikipedia on Answers.com:
Top
Quinone
Not to be confused with quinine.
A quinone is a class of organic compounds that are formally "derived from aromatic compounds [such as benzene or naphthalene] 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."[1] 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.
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.
|
Contents
|
Occurrence and uses
Production of hydrogen peroxide
A large scale industrial application of quinones is for the production of hydrogen peroxide. 2-Alkylanthraquinones are hydrogenated to the corresponding hydroquinones (quinizarins), which then transfer H2 to oxygen:
- dihydroanthraquinone + O2 → anthraquinone + H2O2
In this way, several billion kilograms of H2O2 are produced annually.[2]
Biochemistry
Derivatives of quinones are common constituents of biologically relevant molecules. Some serve as electron acceptors in electron transport chains such as those in photosynthesis (plastoquinone, phylloquinone), and aerobic respiration (ubiquinone). Phylloquinone is also known as Vitamin K1 as it is used by animals to help form certain proteins, which are involved in blood coagulation, bone formation, and other processes.
A natural example of the oxidation of hydroquinone to quinone is in the spray of bombardier beetles; hydroquinone is reacted with hydrogen peroxide to produce a fiery blast of steam, a strong deterrent in the animal world.
Medicinal Uses
Natural or synthetic quinones show a biological or pharmacological activity, and some of them show antitumoral activity. possess a number of biological properties, including some claims in herbal medicine. These applications include purgative (sennosdes), antimicrobacterial (rhein- and saprorthoquinone), anti-tumor (emodin and jugone), inhibition of PGE2 biosynthesis (arnebinone and arnebifuranone) and anti-cardiovascular disease (tanshinone).[3]
Dyes
Many natural and artificial coloring substances (dyes and pigments) are quinone derivatives. They are second only to azo dyes in importance as dyestuffs, with particular emphasis on blue colors. Alizarin (2,3-dihydroxy-9,10-anthraquinone), extracted from the madder plant, was the first natural dye to be synthesized from coal tar.
Reagents in organic chemistry
Benzoquinone is used in organic chemistry as an oxidizing agent. Stronger quinone oxidising agents exist; for instance: chloranil and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (also known as DDQ).[4]
Nomenclature
Quinones are commonly named with a prefix that indicates the parent aromatic hydrocarbon ("benzo-" for benzene, "naphtho-" for naphthalene, "anthra-" for anthracene, etc.) and the "-quinone" suffix. Infix multipliers "-di-", "-tri-", "-tetra-" (etc.) are used when there are 4, 6, 8 (etc.) carbonyls. The position of the carbonyl groups can be indicated before the prefix (as in "1,4,5,8-naphthodiquinone") or after it ("anthra-1,4-quinone").
See also
References
- ^ Nic, M.; Jirat, J.; Kosata, B., eds. (2006–). "Quinones". IUPAC Compendium of Chemical Terminology (Online ed.). doi:10.1351/goldbook.{{{file}}}. ISBN 0-9678550-9-8. http://goldbook.iupac.org/Q05015.html.
- ^ Gustaaf Goor, Jürgen Glenneberg, Sylvia Jacobi “Hydrogen Peroxide” in Ullmann's Encyclopedia of Industrial Chemistry 2007, Wiley-VCH, Weinheim. doi: 10.1002/14356007.a13_443.pub2.
- ^ Liu H., "Extraction and Isolation of Compounds from Herbal Medicines" in 'Traditional Herbal Medicine Research Methods', ed by Willow JH Liu 2011 John Wiley and Sons, Inc.
- ^ March, Jerry (1985), Advanced Organic Chemistry: Reactions, Mechanisms, and Structure (3rd ed.), New York: Wiley, ISBN 0-471-85472-7
External links
This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)
Post a question - any question - to the WikiAnswers community:
Copyrights:
American Heritage Dictionary
The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.
Read more
Britannica Concise Encyclopedia
Britannica Concise Encyclopedia. © 1994-2012 Encyclopædia Britannica, Inc. All rights reserved. Read more
McGraw-Hill Science & Technology Encyclopedia
McGraw-Hill Encyclopedia of Science and Technology. Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved.
Read more
Word Tutor
Copyright © 2004-present by eSpindle Learning, a 501(c) nonprofit organization. All rights reserved.
eSpindle provides personalized spelling and vocabulary tutoring online; sign up free. Read more
eSpindle provides personalized spelling and vocabulary tutoring online; sign up free. Read more
Oxford Dictionary of Biochemistry
Oxford University Press. Oxford Dictionary of Biochemistry and Molecular Biology © 1997, 2000, 2006 All rights reserved.
Read more
