Guaiacol

Guaiacol

Names
IUPAC name 2-methoxyphenol
Other names o-Methoxyphenol; Methylcatechol
Identifiers
CAS Number	90-05-1 Y
ChEBI	CHEBI:28591 Y
ChEMBL	ChEMBL13766 Y
ChemSpider	447 Y
Jmol 3D model	Interactive image
KEGG	D00117 Y
PubChem	460
UNII	6JKA7MAH9C Y
InChI InChI=1S/C7H8O2/c1-9-7-5-3-2-4-6(7)8/h2-5,8H,1H3 Y Key: LHGVFZTZFXWLCP-UHFFFAOYSA-N Y InChI=1/C7H8O2/c1-9-7-5-3-2-4-6(7)8/h2-5,8H,1H3 Key: LHGVFZTZFXWLCP-UHFFFAOYAI
SMILES COc1ccccc1O
Properties
Chemical formula	C7H8O2
Molar mass	124.14 g/mol
Density	1.112 g/cm3, liquid 1.129 g/cm3, crystals
Melting point	28 °C (82 °F; 301 K)
Boiling point	204 to 206 °C (399 to 403 °F; 477 to 479 K)
Vapor pressure	{{{value}}}
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Y verify (what is YN ?)
Infobox references

Guaiacol is a naturally occurring organic compound with the formula C₆H₄(OH)(OCH₃), first isolated by Otto Unverdorben in 1826. Although it is biosynthesized by a variety of organisms, this yellowish 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

In industry, guaiacol is produced 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 an indicator in chemical reactions that produce oxygen. When oxygen binds to it, the complex turns yellowish brown and absorbs light maximally at about 470 nm.

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.

Locust pheromone

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.