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Catecholate

Catechol
Skeletal formula
Ball-and-stick model
Names
Preferred IUPAC name
Benzene-1,2-diol
Other names
Pyrocatechol
1,2-Benzenediol
2-Hydroxyphenol
1,2-Dihydroxybenzene
o-Benzenediol
o-Dihydroxybenzene
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.004.025
EC Number 204-427-5
KEGG
PubChem CID
RTECS number UX1050000
Properties
C6H6O2
Molar mass 110.1 g/mol
Appearance white to brown feathery crystals
Odor faint, phenolic odor
Density 1.344 g/cm3, solid
Melting point 105 °C (221 °F; 378 K)
Boiling point 245.5 °C (473.9 °F; 518.6 K) (sublimes)
430 g/L
Solubility very soluble in pyridine
soluble in chloroform, benzene, CCl4, ether, ethyl acetate
log P 0.88
Vapor pressure 20 Pa (20 °C)
Acidity (pKa) 9.48
-68.76·10−6 cm3/mol
1.604
2.62±0.03 D
Structure
monoclinic
Hazards
Safety data sheet Sigma-Aldrich
Harmful (Xn)
R-phrases (outdated) R21/22, R36/38
S-phrases (outdated) (S2), S22, S26, S37
NFPA 704
Flammability code 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g., canola oil Health code 3: Short exposure could cause serious temporary or residual injury. E.g., chlorine gas Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazards (white): no codeNFPA 704 four-colored diamond
Flash point 127 °C (261 °F; 400 K)
510 °C (950 °F; 783 K)
Explosive limits 1.4%-?
Lethal dose or concentration (LD, LC):
LD50 (median dose)
300 mg/kg (rat, oral)
US health exposure limits (NIOSH):
PEL (Permissible)
none
REL (Recommended)
TWA 5 ppm (20 mg/m3) [skin]
IDLH (Immediate danger)
N.D.
Related compounds
Related benzenediols
Resorcinol
Hydroquinone
Related compounds
1,2-benzoquinone
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Catechol (/ˈkætɪɒl/), also known as pyrocatechol or 1,2-dihydroxybenzene, is an organic compound with the molecular formula C6H4(OH)2. 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 million kg are now synthetically produced annually as a commodity organic chemical, mainly as a precursor to pesticides, flavors, and fragrances.

Catechol occurs as feathery white crystals that are very rapidly soluble in water.

(The name "catechol" has also been used as a chemical class name, where it refers generally to the catechins.)

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 L.f). 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.


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