[gwahy-uh-kohl, -kawl]
Guaiacol is a naturally occurring organic compound with the formula C6H4(OH)(OCH3). This colourless aromatic oil is 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.

Preparation and derivatives

Guaiacol is obtained directly from beechwood tar. It is produced industrially from pyrocatechin by methylation with potash and potassium methyl sulfate, or from anisole by nitration, reduction of the resulting ortho-nitroanisole to 2-aminoanisole, which is then diazotized and boiled with water. In the laboratory, it can be synthesized by the di-methylation of catechol followed by selective mono-demethylation.
C6H4(OH)2 + 2 (CH3O)2SO2 → C6H4(OCH3)2 + 2 HO(CH3O)SO2
C6H4(OCH3)2 + C2H5SNa → C6H4(OCH3)(OH)

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 appears as guaiamar.


Guaiacol is used medicinally as an expectorant, antiseptic, and local anesthetic. Guaiacol is also used in the preparation of eugenol and vanillin. The related derivative, dimethoxybenzene or veratrol, is also used in medicine.

Because of its natural color changing abilities, it is sometimes used as an indicator solution in various experiments involving enzymes.


See also

  • Merck Index, 13th Edition, 4568.

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