Guaiacol: Difference between revisions
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{{short description|Methoxyphenol compound, constituent of plant lignins and essential oils}} |
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{{chembox |
{{chembox |
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| Watchedfields = changed |
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| verifiedrevid = |
| verifiedrevid = 443849411 |
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|Reference=<ref>''[[Merck Index]]'', 13th Edition, '''4568'''.</ref> |
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| Reference =<ref>{{cite book|title=Merck Index|edition=13th|page=4568|title-link=Merck Index}}</ref> |
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|ImageFileL1=Guaiacol.png |
| ImageFileL1 =Guaiacol.png |
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|ImageSizeL1=130px |
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|ImageFileR1=Guaiacol 3D.png |
| ImageFileR1 =Guaiacol 3D spacefill.png |
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| PIN =2-Methoxyphenol |
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|ImageSizeR1 = 120px |
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⚫ | | OtherNames =''o''-Methoxyphenol<br>''O''-Methylcatechol<ref>{{cite web|url=http://www.chemindustry.com/chemicals/464173.html|website=Chemindustry|title=List of synonyms for guaiacol}}</ref><br> 2-Hydroxyanisole<br> Pyroguaiac acid<br> Pyrocatechol monomethyl ether<br> 1-hydroxy-2-methoxybenzene<br> |
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|IUPACName=2-methoxyphenol |
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| UNII = 6JKA7MAH9C |
| UNII = 6JKA7MAH9C |
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| KEGG_Ref = {{keggcite|correct|kegg}} |
| KEGG_Ref = {{keggcite|correct|kegg}} |
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| StdInChIKey = LHGVFZTZFXWLCP-UHFFFAOYSA-N |
| StdInChIKey = LHGVFZTZFXWLCP-UHFFFAOYSA-N |
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| CASNo_Ref = {{cascite|correct|CAS}} |
| CASNo_Ref = {{cascite|correct|CAS}} |
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| CASNo=90-05-1 |
| CASNo = 90-05-1 |
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| PubChem = 460 |
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| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}} |
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| ChemSpiderID = 447 |
| ChemSpiderID = 447 |
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| ChEBI_Ref = {{ebicite|correct|EBI}} |
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| ChEBI = 28591 |
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| SMILES = COc1ccccc1O |
| SMILES = COc1ccccc1O |
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}} |
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|Section2= |
|Section2={{Chembox Properties |
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| C=7|H=8|O=2 |
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| Formula=C<sub>7</sub>H<sub>8</sub>O<sub>2</sub> |
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| MolarMass = |
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| Appearance = colorless oil or crystalline solid |
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| Density = 1.112 g/cm<sup>3</sup>, liquid<br />1.129 g/cm<sup>3</sup>, crystals |
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| MeltingPtC = 26-29 |
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| BoilingPtC = 204–206 |
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| BoilingPt=204-206 °C |
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| BoilingPt_notes = |
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| Solubility= |
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| Solubility = 23.3 g/L at 25 °C |
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}} |
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|Section3= |
|Section3={{Chembox Hazards |
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| MainHazards= |
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| MainHazards = |
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| FlashPt= |
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| FlashPt = |
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| Autoignition= |
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| AutoignitionPt = |
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}} |
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|Section4={{Chembox Related |
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| OtherFunction_label = [[methoxyphenol]]s |
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| OtherFunction = [[Mequinol]]<br /> [[3-Methoxyphenol]] |
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'''Guaiacol''' ({{IPAc-en|ˈ|ɡ|w|aɪ|ə|k|ɒ|l}}) is an [[organic compound]] with the [[Chemical formula|formula]] C<sub>6</sub>H<sub>4</sub>(OH)(OCH<sub>3</sub>). It is a phenolic compound containing a [[methoxy]] functional group. Guaiacol appears as a viscous colorless oil, although aged or impure samples are often yellowish. It occurs widely in nature and is a common product of the [[pyrolysis]] of wood.<ref name=Ullmann/> |
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'''Guaiacol''' is a naturally occurring [[organic compound]] with the [[Chemical formula|formula]] C<sub>6</sub>H<sub>4</sub>(OH)(OCH<sub>3</sub>). Although it is biosynthesized by a variety of organisms,<ref>See for example, {{cite journal | doi = 10.1016/0305-0491(77)90029-3 | author = Duffey, S. S.; Aldrich, J. R.; Blum, M. S. | title = Biosynthesis of phenol and guaiacol by the hemipteran Leptoglossus phyllopus | journal = Comparative Biochemistry and Physiology, Part B: Biochemistry & Molecular Biology | year = 1977 | volume = 56 | issue = 2B | pages = 101–102}}</ref> 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.<ref>{{cite journal | doi = 10.1021/jf0341767 | year = 2003 | month = Sep | author = Dorfner, R; Ferge, T; Kettrup, A; Zimmermann, R; Yeretzian, C | title = Real-time monitoring of 4-vinylguaiacol, guaiacol, and phenol during coffee roasting by resonant laser ionization time-of-flight mass spectrometry | volume = 51 | issue = 19 | pages = 5768–5773 | issn = 0021-8561 | pmid = 12952431 | journal = Journal of agricultural and food chemistry}}</ref> |
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==Occurrence== |
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Guaiacol is usually derived from [[guaiacum]] or wood [[creosote]]. |
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It is produced by a variety of plants.<ref>{{cite journal | doi = 10.1016/0305-0491(77)90029-3 |pmid=830476 |last1=Duffey |first1=S. S. |last2=Aldrich |first2=J. R. |last3=Blum |first3=M. S. | title = Biosynthesis of phenol and guaiacol by the hemipteran ''Leptoglossus phyllopus'' | journal = Comparative Biochemistry and Physiology B | year = 1977 | volume = 56 | issue = 2B | pages = 101–102}}</ref> It is also found in essential oils from [[celery]] seeds, [[tobacco]] leaves, [[Orange (tree)|orange]] leaves, and [[lemon]] peels.<ref>{{cite book |last=Burdock|first=G. A.|date=1995|title=Encyclopedia of Food and Color Additives|location=Boca Raton, FL|publisher=CRC Press|pages=1244–1245|isbn=978-0849394126}}</ref> The pure substance is colorless, but samples become yellow upon exposure to air and light. The compound is present in wood [[smoke]], resulting from the [[pyrolysis]] of [[lignin]]. The compound contributes to the flavor of many substances such as [[whisky|whiskey]]<ref>{{cite news |last=Gallegos |first=Jenna |date=August 17, 2017 |title=The best way to drink whiskey, according to science |newspaper=The Washington Post |url=https://www.washingtonpost.com/news/speaking-of-science/wp/2017/08/17/the-best-way-to-drink-whiskey-according-to-science/ |quote=Guaiacol is what gives whiskey that smoky, spicy, peaty flavor.}}</ref> and [[roasted coffee]].<ref>{{cite journal |last1=Dorfner |first1=R. |last2=Ferge |first2=T. |last3=Kettrup |first3=A. |last4=Zimmermann |first4=R. |last5=Yeretzian |first5=C. |date=Sep 2003 |title=Real-time monitoring of 4-vinylguaiacol, guaiacol, and phenol during coffee roasting by resonant laser ionization time-of-flight mass spectrometry |journal=Journal of Agricultural and Food Chemistry |issn=0021-8561 |doi=10.1021/jf0341767 |pmid=12952431 |volume=51 |issue=19 |pages=5768–5773}}</ref> |
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==Preparation== |
==Preparation== |
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The compound was first isolated by [[Otto Unverdorben]] in 1826.<ref>{{cite journal|last1=Stevens |first1=M. E. |last2=Ronan |first2=A. K. |last3=Sourkes |first3=T. S. |first4=Boyd |last4=E. M. | title=On the Expectorant Action of Creosote and the Guaiacols | journal=Canadian Medical Association Journal | year= 1943 | volume= 48 | issue= 2 | pages= 124–127 | pmid=20322688 | pmc=1827660}}</ref> Guaiacol is produced by [[methylation]] of ''o''-[[catechol]], for example using [[potash]] and [[dimethyl sulfate]]:<ref name=Ullmann>{{Ullmann|first1=Helmut |last1=Fiege |first2=Heinz-Werner |last2=Voges |first3=Toshikazu |last3=Hamamoto |first4=Sumio |last4=Umemura |first5=Tadao |last5=Iwata |first6=Hisaya |last6=Miki |first7=Yasuhiro |last7=Fujita |first8=Hans-Josef |last8=Buysch |first9=Dorothea |last9=Garbe |first10=Wilfried |last10=Paulus |title=Phenol Derivatives|doi=10.1002/14356007.a19_313}}</ref> |
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:C<sub>6</sub>H<sub>4</sub>(OH)<sub>2</sub> + [[Dimethyl sulfate|(CH<sub>3</sub>O)<sub>2</sub>SO<sub>2</sub>]] → C<sub>6</sub>H<sub>4</sub>(OH)(OCH<sub>3</sub>) + HO(CH<sub>3</sub>O)SO<sub>2</sub> |
:C<sub>6</sub>H<sub>4</sub>(OH)<sub>2</sub> + [[Dimethyl sulfate|(CH<sub>3</sub>O)<sub>2</sub>SO<sub>2</sub>]] → C<sub>6</sub>H<sub>4</sub>(OH)(OCH<sub>3</sub>) + HO(CH<sub>3</sub>O)SO<sub>2</sub> |
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===Laboratory methods=== |
===Laboratory methods=== |
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Guaiacol can be prepared by diverse routes in the laboratory. |
Guaiacol can be prepared by diverse routes in the laboratory. [[o-Anisidine|''o''-Anisidine]], derived in two steps from [[anisole]], can be hydrolyzed via its [[diazonium]] derivative. Guaiacol can be synthesized by the [[methylation|dimethylation]] of [[catechol]] followed by selective mono-[[demethylation]].<ref>{{OrgSynth | first1= R. N. |last1=Mirrington |first2= G. I. |last2=Feutrill | year = 1988 | title = Orcinol Monomethyl Ether | collvol = 6 | collvolpages = 859 | prep = cv6p0859}}</ref> |
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:C<sub>6</sub>H<sub>4</sub>(OCH<sub>3</sub>)<sub>2</sub> + |
:C<sub>6</sub>H<sub>4</sub>(OCH<sub>3</sub>)<sub>2</sub> + C<sub>2</sub>H<sub>5</sub>SNa → C<sub>6</sub>H<sub>4</sub>(OCH<sub>3</sub>)(ONa) + C<sub>2</sub>H<sub>5</sub>SCH<sub>3</sub> |
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==Uses== |
==Uses and chemical reactions== |
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===Syringyl/guaiacyl ratio=== |
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Guaiacol is a precursor to various [[flavorant]]s such as [[eugenol]]<ref>{{OrgSynth | author = C. F. H. Allen and J. W. Gates, Jr. | title = ''o''-Eugenol | collvol = 3 | collvolpages = 418 | year = 1955 | prep = cv30418}}</ref> and [[vanillin]].<ref>{{cite encyclopedia |
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[[Lignin]], comprising a major fraction of biomass, is sometimes classified according to the '''guaiacyl''' component. Pyrolysis of lignin from [[gymnosperm]]s gives more guaiacol, resulting from removal of the [[propenyl]] group of [[coniferyl alcohol]]. These lignins are said to have a high guaiacyl (or G) content. In contrast, lignins derived from [[sinapyl alcohol]] affords [[syringol]]. A high syringyl (or S) content is indicative of lignin from [[angiosperm]]s.<ref name=TPC>{{cite journal |doi=10.1105/tpc.010111|title=The Last Step of Syringyl Monolignol Biosynthesis in Angiosperms is Regulated by a Novel Gene Encoding Sinapyl Alcohol Dehydrogenase |year=2001 |last1=Li |first1=Laigeng |last2=Cheng |first2=Xiao Fei |last3=Leshkevich |first3=Jacqueline |last4=Umezawa |first4=Toshiaki |last5=Harding |first5=Scott A. |last6=Chiang |first6=Vincent L. |journal=The Plant Cell |volume=13 |issue=7 |pages=1567–1586 |pmid=11449052 |pmc=139549 }}</ref> Sugarcane [[bagasse]] is one useful source of guaiacol; pyrolysis of the bagasse lignins yields compounds including guaiacol, 4-methylguaiacol and 4-vinylguaiacol.<ref>{{Cite journal |last1=del Río |first1=José C. |last2=Lino |first2=Alessandro G. |last3=Colodette |first3=Jorge L. |last4=Lima |first4=Claudio F. |last5=Gutiérrez |first5=Ana |last6=Martínez |first6=Ángel T. |last7=Lu |first7=Fachuang |last8=Ralph |first8=John |last9=Rencoret |first9=Jorge |date=2015-10-01 |title=Differences in the chemical structure of the lignins from sugarcane bagasse and straw |journal=Biomass and Bioenergy |language=en |volume=81 |pages=322–338 |doi=10.1016/j.biombioe.2015.07.006 |issn=0961-9534|doi-access=free }}</ref> |
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===Chemical intermediate=== |
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| coauthors = K. Formanek, G. Kientz, F. Mauger, V. Maureaux, G. Robert, and F. Truchet |
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Guaiacol is a useful precursor for the synthesis of other compounds.<ref>{{cite journal|doi=10.1351/pac200577071221|title=Masked ''o''-benzoquinone strategy in organic synthesis: Short and efficient construction of ''cis''-decalins and linear triquinanes from 2-methoxyphenols|journal=Pure and Applied Chemistry|volume=77|issue=7|pages=1221–1234|year=2005|last1=Liao|first1=Chun-Chen|doi-access=free}}</ref> Being derived from biomass, it is a potential component or precursor to "green fuels".<ref>{{cite journal|doi=10.1039/C3EE43081B|title=Upgrading of lignin-derived bio-oils by catalytic hydrodeoxygenation|journal=Energy Environ. Sci.|volume=7|pages=103–129|year=2014|last1=Saidi|first1=Majid|last2=Samimi|first2=Fereshteh|last3=Karimipourfard|first3=Dornaz|last4=Nimmanwudipong|first4=Tarit|last5=Gates|first5=Bruce C.|last6=Rahimpour|first6=Mohammad Reza}}</ref> |
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Guaiacol is also a useful reagent for the quantification of [[peroxidase]]s, as in the presence of [[hydrogen peroxide]] these enzymes will catalyse with it the formation of tetraguaiacol,<ref>{{cite journal | vauthors = Koduri RS, Tien M | journal = Journal of Biological Chemistry | volume = 270 | issue = 38 | pages = 22254–8 | date = 1995 | pmid = 7673205 | doi = 10.1074/jbc.270.38.22254 | title = Oxidation of Guaiacol by Lignin Peroxidase. Role of veratryl alcohol | doi-access = free }}</ref> a coloured compound that can be quantified by its absorbance at 420–470 nm, following the equation: |
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:4 {{chem|guaiacol (colorless)}} + 2 {{chem|H|2|O|2}} → {{chem|tetraguaiacol (colored)}} + 8 {{chem|H|2|O}}. |
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===Medicinal and food=== |
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Guaiacol is a precursor to various [[flavorant]]s, such as [[eugenol]].<ref>{{OrgSynth | first1= C. F. H. |last1=Allen |first2=J. W. Jr |last2=Gates | title = ''o''-Eugenol | collvol = 3 | collvolpages = 418 | year = 1955 | prep = cv3P0418}}</ref> An estimated 85% of the world's supply of [[vanillin]] comes from guaiacol. Because consumers tend to prefer natural vanillin to synthetic vanillin, methods such as microbial fermentation have been adopted. The route entails the [[condensation reaction]] of [[glyoxylic acid]] with guaiacol to give mandelic acid, which is oxidized to produce [[phenylglyoxylic acid]]. This acid undergoes a decarboxylation to afford vanillin.<ref>{{cite encyclopedia |
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| first2=K. |last2=Formanek |first3=G. |last3=Kientz |first4=F. |last4=Mauger |first5=V. |last5=Maureaux |first6=G. |last6=Robert |first7=F. |last7=Truchet |
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| title = Vanillin |
| title = Vanillin |
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| encyclopedia = |
| encyclopedia = Kirk–Othmer Encyclopedia of Chemical Technology |edition=4th |
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| volume = 24 |
| volume = 24 |
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| pages = 812–825 |
| pages = 812–825 |
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| publisher = John Wiley & Sons |
| publisher = John Wiley & Sons |
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| location = New York |
| location = New York, NY |
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| year = 1997}}</ref> |
| year = 1997}}</ref> The crude vanillin product can then be purified with vacuum distillation and recrystallization. |
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It also can be used as a dye in chemical reactions, as oxygen will turn guaiacol from colorless to brown. |
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Guaiacol is also used medicinally as an [[expectorant]], [[antiseptic]], and local [[anesthetic]].<ref>{{cite web |url=https://www.drugbank.ca/drugs/DB11359|title=Guaiacol|author=<!--Not stated--> |date=2019-11-02|website=DrugBank|access-date=2019-11-18}}</ref> |
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==Related compounds== |
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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|date=October 2007}} 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. |
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⚫ | Guaiacol is produced in the gut of [[desert locust]]s, ''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]].<ref>{{cite journal|doi=10.1038/35002669|pmid=10706273|title=Pheromones: Exploitation of gut bacteria in the locust|first1=Rod J.|last1=Dillon|first2=Chris T.|last2=Vennard|first3=A. Keith|last3=Charnley|journal=Nature|volume=403|issue=6772|page=851|date=2000-02-24|bibcode=2000Natur.403..851D|s2cid=5207502|doi-access=free}}</ref> |
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Guaiacol is used as an inducer in Biochemical transformation. It has powerful effect on the fungi culture to incite them for producing the enzyme in their liquid or agar culture.<ref>[http://www.jbc.org/content/268/32/23954.abstract JBC Journal of Biological Chemistry]</ref><ref>[http://www.pnas.org/content/92/24/11312.abstract PNAS, National Academy of Sciences of the United States of America]</ref> |
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==Safety== |
==Safety== |
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[[Methoxyphenol]]s 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.<ref>{{cite web|last=Smith|first=K. R.|date=2005|url=http://ehs.sph.berkeley.edu/krsmith/publications/2005%20pubs/HC%20woodsmoke%20report%20Mar%2031%2005%20%28rev%29.pdf |title=Critical review of the health effects of woodsmoke|publisher=School of Public Health, University of Berkeley|url-status=dead|archive-url=https://web.archive.org/web/20090710235756/http://ehs.sph.berkeley.edu/krsmith/publications/2005%20pubs/HC%20woodsmoke%20report%20Mar%2031%2005%20%28rev%29.pdf|archive-date=2009-07-10}}</ref> |
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== See also == |
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* [[Creosote]] |
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⚫ | Guaiacol is produced in the gut of [[ |
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* [[Guaifenesin]] |
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==References== |
== References == |
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{{reflist}} |
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{{Authority control}} |
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[[Category:Phenol ethers]] |
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[[Category:Flavors]] |
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[[de:Guajacol]] |
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[[fr:Gaïacol]] |
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[[Category:Substances discovered in the 19th century]] |
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[[it:Guaiacolo]] |
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[[hu:Gvajakol]] |
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[[nl:Guaiacol]] |
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[[ja:グアイアコール]] |
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[[pl:Gwajakol]] |
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[[pt:Guaiacol]] |
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[[ru:Гваякол]] |
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[[zh:愈创木酚]] |