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Guaiacol is a naturally occurring organic compound with the formula C₆H₄(OH)(OCH₃), first isolated by Otto Unverdorben in 1826.^[3] Although it is biosynthesized by a variety of organisms,^[4] 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.^[5]

Preparation

In industry, guaiacol is produced by methylation of catechol, e.g., using potash and dimethyl sulfate:^[6]

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.^[7]

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

Uses

Guaiacol is a precursor to various flavorants, such as eugenol^[8] and vanillin.^[9] 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).^{[citation needed]} 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.^[10]

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.^[11]

References

^ Merck Index, 13th Edition, 4568.
^ Chemindustry list of synonyms for guaiacol
^ Stevens ME, Ronan AK, Sourkes TS, Boyd EM (1943). "On the Expectorant Action of Creosote and the Guaiacols.". Can Med Assoc J 48 (2): 124–7. PMID 20322688.
^ See for example, Duffey, S. S.; Aldrich, J. R.; Blum, M. S. (1977). "Biosynthesis of phenol and guaiacol by the hemipteran Leptoglossus phyllopus". Comparative Biochemistry and Physiology, Part B: Biochemistry & Molecular Biology 56 (2B): 101–102. doi:10.1016/0305-0491(77)90029-3.
^ Dorfner, R; Ferge, T; Kettrup, A; Zimmermann, R; Yeretzian, C (Sep 2003). "Real-time monitoring of 4-vinylguaiacol, guaiacol, and phenol during coffee roasting by resonant laser ionization time-of-flight mass spectrometry". Journal of Agricultural and Food Chemistry 51 (19): 5768–5773. doi:10.1021/jf0341767. ISSN 0021-8561. PMID 12952431.
^ Helmut Fiege, Heinz-Werner Voges, Toshikazu Hamamoto, Sumio Umemura, Tadao Iwata, Hisaya Miki, Yasuhiro Fujita, Hans-Josef Buysch, Dorothea Garbe, Wilfried Paulus "Phenol Derivatives" Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2002. doi:10.1002/14356007.a19_313
^ R. N. Mirrington and G. I. Feutrill (1988). "Orcinol Monomethyl Ether". Org. Synth. ; Coll. Vol. 6, p. 859
^ C. F. H. Allen and J. W. Gates, Jr. (1955). "o-Eugenol". Org. Synth. ; Coll. Vol. 3, p. 418
^ Esposito, Lawrence J.; K. Formanek; G. Kientz; F. Mauger; V. Maureaux; G. Robert; F. Truchet (1997). "Vanillin". Kirk-Othmer Encyclopedia of Chemical Technology, 4th edition 24. New York: John Wiley & Sons. pp. 812–825.
^ CRITICAL REVIEW OF THE HEALTH EFFECTS OF WOODSMOKE
^ Nature, Pheromones: Exploitation of gut bacteria in the locust

English Journal

A comparative study on aromatic profiles of strawberry vinegars obtained using different conditions in the production process.

Ubeda C1, Callejón RM2, Troncoso AM2, Moreno-Rojas JM3, Peña F3, Morales ML4.
Food chemistry.Food Chem.2016 Feb 1;192:1051-9. doi: 10.1016/j.foodchem.2015.07.091. Epub 2015 Jul 23.
Impact odorants in strawberry vinegars produced in different containers (glass, oak and cherry barrels) were determined by gas chromatography-olfactometry using modified frequency (MF) technique, and dynamic headspace gas chromatography-mass spectrometry. Aromatic profile of vinegar from strawberry
PMID 26304447

Pressurized liquid extraction of phenolic compounds from rice (Oryza sativa) grains.

Setyaningsih W1, Saputro IE2, Palma M3, Barroso CG2.
Food chemistry.Food Chem.2016 Feb 1;192:452-9. doi: 10.1016/j.foodchem.2015.06.102. Epub 2015 Jun 30.
An analytical pressurized liquid extraction (PLE) process has been studied for the extraction of phenolic compounds from rice grains. A fractional factorial design (2(7-2)) with a centre point was used to optimize PLE parameters such as solvent composition (EtOAc in MeOH), extraction temperature, pr
PMID 26304372

Effects of preservatives on Alicyclobacillus acidoterrestris growth and guaiacol production.

Cai R1, Yuan Y1, Wang Z1, Guo C1, Liu B1, Pan C1, Liu L1, Yue T2.
International journal of food microbiology.Int J Food Microbiol.2015 Dec 2;214:145-50. doi: 10.1016/j.ijfoodmicro.2015.08.013. Epub 2015 Aug 20.
Alicyclobacillus acidoterrestris can survive the pasteurization process, multiply in pasteurized juices and produce guaiacol which causes medicinal or antiseptic off-flavors. Chemical preservatives have the potential to suppress outgrowth of surviving populations during subsequent storage of fruit j
PMID 26301383

Japanese Journal

Participation of Hydroxyl Radical in the Formation of Verdoheme-type Compound in the Reaction of a Ferric Porphyrin with Hydrogen Peroxide

Chemistry Letters 46(4), 509-512, 2017
NAID 130005549090

Characterization of an O-methyltransferase specific to guaiacol-type benzenoids from the flowers of loquat (Eriobotrya japonica)

Journal of bioscience and bioengineering 122(6), 679-684, 2016-12
NAID 40021044912

全国新酒鑑評会出品酒の「香辛料様・4VG」の特性に関与する香気成分

日本醸造協会誌 111(7), 483-492, 2016-07
NAID 40020907118

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★リンクテーブル★

リンク元	「グアヤコール」
拡張検索	「potassium guaiacolsulfonate」「guaiacolsulfonate」
関連記事	「guaiac」

「グアヤコール」

Guaiacol^[1]
Names
	IUPAC name 2-methoxyphenol
	Other names o-Methoxyphenol; Methylcatechol
Identifiers
CAS Registry Number	90-05-1
ChEBI	CHEBI:28591
ChEMBL	ChEMBL13766
ChemSpider	447
	InChI InChI=1S/C7H8O2/c1-9-7-5-3-2-4-6(7)8/h2-5,8H,1H3 ; Key: LHGVFZTZFXWLCP-UHFFFAOYSA-N ; InChI=1/C7H8O2/c1-9-7-5-3-2-4-6(7)8/h2-5,8H,1H3; Key: LHGVFZTZFXWLCP-UHFFFAOYAI ;
Jmol-3D images	Image
KEGG	D00117
PubChem	460
	SMILES COc1ccccc1O ;
UNII	6JKA7MAH9C
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)
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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	Infobox references