Guaiacol

Guaiacol
File:Guaiacol2.png	File:Guaiacol 3D.png
IUPAC name 2-methoxyphenol
Other names o-Methoxyphenol; Methylcatechol
style="background: #F8EABA; text-align: center;" colspan="2" | Identifiers
CAS number	90-05-1 Y
PubChem	460
ChemSpider	447
SMILES
style="background: #F8EABA; text-align: center;" colspan="2" | 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
Y (what is this?)  (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Guaiacol is a naturally occurring organic compound with the formula C₆H₄(OH)(OCH₃). Although it is biosynthesized by a variety of organisms, 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.

Preparation

Guaiacol is produced industrially by methylation of catechol, e.g. using potash and dimethyl sulfate:

C₆H₄(OH)₂ + (CH₃O)₂SO₂ → C₆H₄(OH)(OCH₃) + HO(CH₃O)SO₂

Laboratory methods

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.

C₆H₄(OCH₃)₂ + C₂H₅SNa → C₆H₄(OCH₃)(ONa) + C₂H₅SCH₃

Uses

Guaiacol is a precursor to various flavorants such as eugenol and vanillin. 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.

Related compounds

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.

Safety

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.

References

cs:Guajakol zh:愈创木酚