Hydroquinone – CFA Equipment manufacturer – Multifunctional Drilling Rig manufac
Nomenclature
Hydroquinone is the name recommended by the International Union of Pure and Applied Chemistry (IUPAC) in its 1993 Recommendations for the Nomenclature of Organic Chemistry
Properties
Hydroquinone can undergo mild oxidation to convert to benzoquinone. Reduction of quinone reverses this reaction back to hydroquinone. Some biochemical compounds in nature have this sort of hydroquinone or quinone section in their structures, such as coenzyme Q, and can undergo similar redox interconversions.
The hydroxyl groups of hydroquinone are quite weakly acidic. Hydroquinone can lose an H+ from one of the hydroxyls to form a monophenolate ion or lose an H+ from both to form a diphenolate ion.
Uses
Hydroquinone has a variety of uses principally associated with its action as a reducing agent which is soluble in water. It is a major component in most photographic developers where, with the compound metol, it reduces silver halides to elemental silver.
In human medicine, hydroquinone is used as a topical application in skin whitening to reduce the color of skin as it does not have the same predisposition to cause dermatitis as metal does. There is inadequate evidence in humans for the carcinogenicity of hydroquinone. This use is banned in some countries, including the member states of the European Union under Directive 76/768/EEC:1976.
The disodium diphenolate salt of hydroquinone is used as an alternating comonomer unit in the production of the polymer PEEK.
As a polymerization inhibitor, hydroquinone prevents polymerization of acrylic acid, methyl methacrylate, etc.
It is also used as a raw material of herbicides, rubber antioxidants, and dyestuffs.
Natural occurrences
Hydroquinones are one of the two primary reagents in the defensive glands of bombardier beetles, along with hydrogen peroxide (and perhaps other chemicals, depending on the species), which collect in a reservoir. The reservoir opens through a muscle-controlled valve onto a thick-walled reaction chamber. This chamber is lined with cells that secrete catalases and peroxidases. When the contents of the reservoir are forced into the reaction chamber, the catalases and peroxidases rapidly break down the hydrogen peroxide and catalyze the oxidation of the hydroquinones into p-quinones. These reactions release free oxygen and generate enough heat to bring the mixture to the boiling point and vaporize about a fifth of it, producing a hot spray from the beetle’s abdomen.
Farnesyl hydroquinone derivatives are the principal irritants exuded by the poodle-dog bush, which can cause severe contact dermatitis in humans.
See also
Pyrocatechol
Resorcinol
Photographic developer
References
^ Panico, R.; & Powell, W. H. (Eds.) (1994). A Guide to IUPAC Nomenclature of Organic Compounds 1993. Oxford: Blackwell Science. ISBN 0-632-03488-2.
^ IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, Volume 71, Re-Evaluation of Some Organic Chemicals, Hydrazine and Hydrogen Peroxide]
^ 76/768/EEC:1976 Council Directive 76/768/EEC of 27 July 1976 on the approximation of the laws of the Member States relating to cosmetic products : http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=CELEX:31976L0768:EN:HTML
^ Example of a product recall in Ireland
External links
International Chemical Safety Card 0166
NIOSH Pocket Guide to Chemical Hazards
IARC Monograph: “Hydroquinone”
European Chemicals Bureau
IUPAC Nomenclature of Organic Chemistry (online version of the “Blue Book”)
v d e
Other dermatological preparations (D11)
Medicated shampoos
Cetrimide – Cadmium compounds – Selenium compounds – Povidone-iodine – Sulfur compounds – Xenysalate
Other dermatologicals
Seborrhoeic dermatitis/dandruff
Lithium succinate Pyrithione zinc
Skin whitening/depigmenting
Hydroquinone Mequinol Monobenzone
Anti-inflammatory/Immunomodulators
Oxaceprol Gamolenic acid Pimecrolimus Tacrolimus Alitretinoin
Baldness treatments
5-alpha-reductase inhibitor (Finasteride) potassium channel opener (Minoxidil)
Hair growth inhibitors
Eflornithine
Other
Calcium gluconate Magnesium sulfate Tiratricol
Categories: Benzenediols | Photographic chemicals | IARC Group 3 carcinogensHidden categories: Chemboxes which contain changes to watched fields
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