|Preferred IUPAC name
Pyrocatechol monomethyl ether
3D model (JSmol)
CompTox Dashboard (EPA)
|Molar mass||124.139 g·mol−1|
|Appearance||colorless oil or crystalline solid|
|Density||1.112 g/cm3, liquid|
1.129 g/cm3, crystals
|Melting point||26–29 °C (79–84 °F; 299–302 K)|
|Boiling point||204–206 °C (399–403 °F; 477–479 K)|
|23.3 g/l at 25 °C|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|what is ?)(|
Guaiacol (//) is a naturally-occurring organic compound with the formula C6H4(OH)(OCH3). Although it is biosynthesized by a variety of organisms, this aromatic oil is usually derived from guaiacum or wood creosote. It is also found in essential oils from celery seeds, tobacco leaves, orange leaves, and lemon peels. The pure substance is colorless, but samples become yellow 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 substances such as whisky and roasted coffee.
- C6H4(OH)2 + (CH3O)2SO2 → C6H4(OH)(OCH3) + HO(CH3O)SO2
Guaiacol can be prepared by diverse routes in the laboratory. o-Anisidine, 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.
- C6H4(OCH3)2 + C2H5SNa → C6H4(OCH3)(ONa) + C2H5SCH3
Uses and chemical reactions
Guaiacol is also a useful reagent for the quantification of peroxidases, as in the presence of hydrogen peroxide these enzymes will catalyse with it the formation of tetraguaiacol, a coloured compound that can be quantified by its absorbance at 420–470 nm, following the equation:
4 guaiacol (colourless) + 2 H
2 → tetraguaiacol (coloured) + 8 H
Medicinal and food
Guaiacol is a precursor to various flavorants, such as eugenol. An estimated 85% of the world's supply of vanillin comes from guaiacol. The route entails condensation of glyoxylic acid with guaiacol to give mandelic acid, which is oxidized to produce a phenylglyoxylic acid. This acid undergoes a decarboxylation to afford vanillin.
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 agglomerans (Enterobacter). It is one of the main components of the pheromones that cause locust swarming.
Methoxyphenols are potential biomarkers of biomass smoke exposure, such as from inhalation of woodsmoke. Dietary sources of methoxyphenols overwhelm the contribution from inhalational exposures to woodsmoke.
- Merck Index (13th ed.). p. 4568.
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- Gallegos, Jenna (August 17, 2017). "The best way to drink whiskey, according to science". The Washington Post.
Guaiacol is what gives whiskey that smoky, spicy, peaty flavor.
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- Sodium ethanethiolate
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