Catechol

Catechol ( or ), also known as pyrocatechol or 1,2-dihydroxybenzene, is an organic compound with the molecular formula . It is the ortho isomer of the three isomeric benzenediols. This colorless compound occurs naturally in trace amounts. It was first discovered by destructive distillation of the plant extract catechin. About 20,000 tonnes of catechol are now synthetically produced annually as a commodity organic chemical, mainly as a precursor to pesticides, flavors, and fragrances. Small amounts of catechol occur in fruits and vegetables.

Catechol ( or ), also known as pyrocatechol or 1,2-dihydroxybenzene, is an organic compound with the molecular formula . It is the ortho isomer of the three isomeric benzenediols. This colorless compound occurs naturally in trace amounts. It was first discovered by destructive distillation of the plant extract catechin. About 20,000 tonnes of catechol are now synthetically produced annually as a commodity organic chemical, mainly as a precursor to pesticides, flavors, and fragrances. Small amounts of catechol occur in fruits and vegetables. ==Isolation and synthesis== Catechol was first isolated in 1839 by Edgar Hugo Emil Reinsch (1809–1884) by distilling it from the solid tannic preparation catechin, which is the residuum of catechu, the boiled or concentrated juice of Mimosa catechu (Acacia catechu). Upon heating catechin above its decomposition point, a substance that Reinsch first named Brenz-Katechusäure (burned catechu acid) sublimated as a white efflorescence. This was a thermal decomposition product of the flavanols in catechin. In 1841, both Wackenroder and Zwenger independently rediscovered catechol; in reporting on their findings, Philosophical Magazine coined the name pyrocatechin. By 1852, Erdmann realized that catechol was benzene with two oxygen atoms added to it; in 1867, August Kekulé realized that catechol was a diol of benzene, so by 1868, catechol was listed as pyrocatechol. In 1879, the Journal of the Chemical Society recommended that catechol be called "catechol", and in the following year, it was listed as such. Catechol has since been shown to occur in free form naturally in kino and in beechwood tar. Its sulfonic acid has been detected in the urine of horses and humans. Catechol is produced industrially by the hydroxylation of phenol using hydrogen peroxide. It can be produced by reaction of salicylaldehyde with base and hydrogen peroxide (Dakin oxidation), as well as the hydrolysis of 2-substituted phenols, especially 2-chlorophenol, with hot aqueous solutions containing alkali metal hydroxides. Its methyl ether derivative, guaiacol, converts to catechol via hydrolysis of the bond as promoted by hydroiodic acid (HI). where X = PCl or POCl; ; CO Basic solutions of catechol react with iron(III) to give the red . Ferric chloride gives a green coloration with the aqueous solution, while the alkaline solution rapidly changes to a green and finally to a black color on exposure to the air. Iron-containing dioxygenase enzymes catalyze the cleavage of catechol. File:DHSA.svg|3,4-dihydroxy-9,10-secoandrosta-1,3,5(10)-triene-9,17-dione, a metabolite of cholesterol File:Catechin structure.svg|Catechin, a component of tea. File:Piceatannol.svg|Piceatannol, an antioxidant found in some red wines. File:Urushiol.svg|Urushiols, the active agent in poison ivy (R = (CH 2 ) 14 CH 3 , (CH 2 ) 7 CH=CHCH 2 CH=CHCH 2 CH=CH 2 , and others) File:Catecholamine.svg|Catecholamines, drugs imitating them (such as MDMA), hormones/neurotransmitters File:Dopamine structure.svg|Dopamine, a well-known neurotransmitter with many important roles in cells File:Quercetin.svg|Quercetin, which is found in many foods. Catechol derivatives are found widely in nature. They often arise by hydroxylation of phenols. Arthropod cuticle consists of chitin linked by a catechol moiety to protein. The cuticle may be strengthened by cross-linking (tanning and sclerotization), in particular, in insects, and of course by biomineralization. The synthetic derivative 4-tert-butylcatechol is used as an antioxidant and polymerization inhibitor.

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