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Pyrogallol is an organic compound with the formula C 6 H 3 (OH) 3. It is a water-soluble, white solid although samples are typically brownish because of its sensitivity toward oxygen. [ 3 ] It is one of three isomers of benzenetriols .
1,2,3,5-Tetrahydroxybenzene, also known as pyrogallol, has various uses. It is used in the production of certain dyes, photographic developers, and hair dyes. Additionally, pyrogallol has been employed in traditional medicine and some cosmetic formulations due to its antioxidant properties.
A hydrolysable tannin or pyrogallol-type tannin is a type of tannin that, on heating with hydrochloric or sulfuric acids, yields gallic or ellagic acids. [ 1 ] At the center of a hydrolysable tannin molecule , there is a carbohydrate (usually D-glucose but also cyclitols like quinic or shikimic acids ).
In enzymology, a pyrogallol 1,2-oxygenase (EC 1.13.11.35) is an enzyme that catalyzes the chemical reaction. 1,2,3-trihydroxybenzene + O 2 (Z)-5-oxohex-2-enedioate. Thus, the two substrates of this enzyme are 1,2,3-trihydroxybenzene and O 2, whereas its product is (Z)-5-oxohex-2-enedioate.
In enzymology, a pyrogallol hydroxytransferase (EC 1.97.1.2) is an enzyme that catalyzes the chemical reaction 1,2,3,5-tetrahydroxybenzene + 1,2,3-trihydroxybenzene ⇌ {\displaystyle \rightleftharpoons } 1,3,5-trihydroxybenzene + 1,2,3,5-tetrahydroxybenzene
The other two isomers are hydroxyquinol (1,2,4-benzenetriol) and pyrogallol (1,2,3-benzenetriol). Phloroglucinol, and its benzenetriol isomers, are still defined as "phenols" according to the IUPAC official nomenclature rules of chemical compounds. Many such monophenolics are often termed polyphenols.
For that reason, the liquid ink needs to be stored in a well-stoppered bottle, and often becomes unusable after a time. The ferric ions react with the tannic acid or some derived compound (possibly gallic acid or pyrogallol) to form a polymeric organometallic compound. [4] While a very effective ink, the formula was less than ideal.
Most polyphenols contain repeating phenolic moieties of pyrocatechol, resorcinol, pyrogallol, and phloroglucinol connected by esters (hydrolyzable tannins) or more stable C-C bonds (nonhydrolyzable condensed tannins). Proanthocyanidins are mostly polymeric units of catechin and epicatechin.