Pyrocatechol
Encyclopedia : P : PY : PYR : Pyrocatechol
| Pyrocatechol | |
|---|---|
| |
| General | |
| Systematic name | Pyrocatechol |
| Other names | Catechol Benzene-1,2-diol o-Benzenediol |
| Molecular formula | C6H4(OH)2 |
| SMILES | OC1=C(O)C=CC=C1 |
| Molar mass | 110.1 g/mol |
| Appearance | white solid |
| CAS number | [120-80-9] |
| Properties | |
| Density and phase | 1.3 g/cm³, solid |
| Solubility in water | 43 g/100 ml (? °C) |
| Melting point | 105 °C |
| Boiling point | 245.5 °C |
| Acidity (pKa) | ? |
| Dipole moment | ? D |
| Hazards | |
| MSDS | External MSDS |
| EU classification | Harmful (Xn) |
| NFPA 704 | |
| R-phrases | R21/22, R36/38 |
| S-phrases | S2, S22, S26, S37 |
| Flash point | 127 °C |
| RTECS number | UX1050000 |
| Supplementary data page | |
| Structure and properties | n, εr, etc. |
| Thermodynamic data | Phase behaviour Solid, liquid, gas |
| Spectral data | UV, IR, NMR, MS |
| Related compounds | |
| Related benzenediols | Resorcinol Hydroquinone |
| Related compounds | 1,2-benzoquinone |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) [Chemical infoboxInfobox disclaimer and references] | |
Pyrocatechol, often known as catechol or benzene-1,2-diol, older name pyrocatechin, is a benzenediol, with formula C6H4(OH)2, first prepared in 1839 by H. Reinsch by distilling catechin (the juice of Mimosa catechu); it occurs free in kino and in beechwood tar; its sulfonic acid is present in the urine of the horse and man.
It results in the alkaline fusion of many resins, and may be prepared by fusing ortho-phenolsulphonic acid, o-chlorphenol, o-bromphenol, and o-phenoldisulphonic acid with potash, or, better, by heating its methyl ether, guaiacol, C6H4(OH)(OCH3), a constituent of beechwood tar, with hydriodic acid.
Pyrocatechin crystallizes in white rhombic prisms, which melt at 104 and boil at 245; it is readily soluble in water, alcohol and ether. Ferric chloride gives a green coloration with the aqueous solution, whilst the alkaline solution rapidly changes to a green and finally to a black color on exposure to the air. It reduces silver solutions in the cold and alkaline copper on heating.
Guaiacol may be obtained directly from beechwood tar, from pyrocatechin by methylation with potash and potassium methyl sulphate at 180, or from anisole by nitration, reduction of the ortho-nitroanisol to amino-anisol, which is then diazotized and boiled with water. It melts at 28 and boils at 250. It is employed in medicine as an expectorant. The dimethyl ether or veratrol is also used in medicine. Many other pyrocatechin derivatives have been suggested for therapeutic application. Guaiacol carbonate is known as duotal, the phosphate as phosphatol, the phosphite as guaiaco-phosphal; phosphotal is a mixture of the phosphites of creosote phenols. The valerianic ester of guaiacol is known as geosote, the henzoic as benzosol, the salicylic as guaiacolsalol, while the glycerin ether appears as guaiamar.
Pyrocatechin readily condenses to form heterocyclic compounds; cyclic esters are formed by phosphorus trichloride and oxychloride, carbonyl chloride, sulphuryl chloride, &c.; whilst ortho-phenylenediamine, o-aminophenol, and o-aminothiophenol give phenazine, phenoxazine and thiodiphenylamine.
Nomenclature
Pyrocatechol is the name recommended by the International Union of Pure and Applied Chemistry (IUPAC) in its 1993 Recommendations for the Nomenclature of Organic Chemistry.[#endnote_BlueBook]Occurrences
Urushiols are naturally existing organic compounds which have the catechol skeleton structure and diphenol functionality but with alkyl groups substituted onto the aromatic ring. Urushiols are the skin-irritating poisons found in plants like poison ivy, etc. Catecholamines are biochemically significant hormones/neurotransmitters which are phenethylamines where the phenyl group has a catechol skeleton structure. Two parts of a molecule of catechin, another natural compound which is found in tea, have the catechol skeleton structure in them.Uses
Pyrocatechol has been used as a film developing chemical.Reference
- ↑
See also
External links
- [International Chemical Safety Card 0411]
- [NIOSH Pocket Guide to Chemical Hazards]
- [IARC Monograph: "Catechol"]
- [European Chemicals Bureau]
- [IUPAC Nomenclature of Organic Chemistry] (online version of the "Blue Book")
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