| Guaiacol[1] | |
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2-methoxyphenol |
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Other names
o-Methoxyphenol; Methylcatechol[2] |
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| Identifiers | |
| CAS number | 90-05-1 |
| PubChem | 460 |
| ChemSpider | 447 |
| UNII | 6JKA7MAH9C |
| KEGG | D00117 |
| ChEBI | CHEBI:28591 |
| ChEMBL | CHEMBL13766 |
| Jmol-3D images | Image 1 |
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| Properties | |
| Molecular formula | C7H8O2 |
| Molar mass | 124.14 g/mol |
| Density | 1.112 g/cm3, liquid 1.129 g/cm3, crystals |
| Melting point |
28 °C, 301 K, 82 °F |
| Boiling point |
204–206 °C |
| (verify) (what is: /?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
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| Infobox references | |
Guaiacol is a naturally occurring organic compound with the formula C6H4(OH)(OCH3), discovered by Ascanio Sobrero. Although it is biosynthesized by a variety of organisms,[3] this colorless aromatic oil is usually derived from guaiacum or wood creosote. Samples darken upon exposure to air and light. Guaiacol is present in wood smoke, resulting from the pyrolysis of lignin. The compound contributes to the flavor of many compounds, e.g. roasted coffee.[4]
Contents |
In industry, guaiacol is produced by methylation of catechol, e.g. using potash and dimethyl sulfate:[5]
Guaiacol can be prepared by diverse routes in the laboratory. 2-Aminoanisole, derived in two steps from anisole, can be hydrolyzed via its diazonium derivative. Guaiacol can be synthesized by the dimethylation of catechol followed by selective mono-demethylation.[6]
Guaiacol is a precursor to various flavorants such as eugenol[7] and vanillin.[8] Its derivatives are used medicinally as an expectorant, antiseptic, and local anesthetic. It also can be used as a dye in chemical reactions, as oxygen will turn guaiacol from colorless to brown.
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 benzoic as benzosol, the salicylic as guaiacolsalol, while the glycerin ether is the drug guaifenesin. The related derivative, dimethoxybenzene or veratrole, is also useful. In preparation of food by smoking, guaiacol is the main chemical responsible for the smoky taste, whereas syringol is responsible for the smoky aroma.
Methoxyphenols are potential biomarkers of biomass smoke exposure, e.g. from inhalation of woodsmoke. Dietary sources of methoxyphenols overwhelm the contribution from inhalational exposures to woodsmoke.[9]
Guaiacol is produced in the gut of Desert locusts, Schistocerca gregaria, by the breakdown of plant material. This process is undertaken by the gut bacterium Pantoea (Enterobacter) agglomerans. Guaiacol is one of the main components of the pheromones that cause locust swarming.[10]