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| Names | |
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| Preferred IUPAC name
5-Methyl-2-(propan-2-yl)phenol[1] | |
| Systematic IUPAC name
5-Methyl-2-(propan-2-yl)benzenol | |
| Other names
2-Isopropyl-5-methylphenol, isopropyl-m-cresol, 1-methyl-3-hydroxy-4-isopropylbenzene, 3-methyl-6-isopropylphenol, 5-methyl-2-(1-methylethyl)phenol, 5-methyl-2-isopropyl-1-phenol, 5-methyl-2-isopropylphenol, 6-isopropyl-3-methylphenol, 6-isopropyl-m-cresol, Apiguard, NSC 11215, NSC 47821, NSC 49142, thyme camphor, m-thymol, and p-cymen-3-ol
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| Identifiers | |
3D model (JSmol)
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| ChEBI | |
| ChEMBL | |
| ChemSpider | |
| DrugBank | |
| ECHA InfoCard | 100.001.768 |
| EC Number |
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| KEGG | |
PubChem CID
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| UNII | |
CompTox Dashboard (EPA)
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| Properties | |
| C10H14O | |
| Molar mass | 150.221 g·mol−1 |
| Density | 0.96 g/cm3 |
| Melting point | 49 to 51 °C (120 to 124 °F; 322 to 324 K) |
| Boiling point | 232 °C (450 °F; 505 K) |
| 0.9 g/L (20 °C)[2] | |
Refractive index (nD)
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1.5208[3] |
| Pharmacology | |
| QP53AX22 (WHO) | |
| Hazards | |
| GHS labelling: | |
  
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| Warning | |
| H302, H314, H411 | |
| P260, P264, P270, P273, P280, P301+P312, P301+P330+P331, P303+P361+P353, P304+P340, P305+P351+P338, P310, P321, P330, P363, P391, P405, P501 | |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Thymol (also known as 2-isopropyl-5-methylphenol, IPMP), C10H14O, is a monoterpenoid, phenol derivative of p-cymene, isomeric with carvacrol.[4] It occurs naturally in oil of thyme and is extracted from Thymus vulgaris (common thyme), ajwain,[5] and various other plants, as a white crystalline substance with a pleasant aromatic odor.[4]
Thymol provides the distinctive flavor of the culinary herb thyme, also produced from T. vulgaris.[4] Thymol is only slightly soluble in water at neutral pH, but due to deprotonation of the phenol, it is highly soluble in alcohols, other organic solvents, and strongly alkaline aqueous solutions.
Chemical synthesis
Thymol is produced by the alkylation of m-cresol and propene.[6][7] CH3C6H4OH + CH2CHCH3 → ((CH3)2CH)CH3C6H3OH
A predicted method of biosynthesis of thymol in thyme and oregano begins with the cyclization of geranyl diphosphate by TvTPS2 to γ-terpinene. Oxidation by a cytochrome P450 in the CYP71D subfamily creates a dienol intermediate, which is then converted into a ketone by short-chain dehydrogenase. Lastly, keto-enol tautomerization gives thymol. Its dissociation constant (pKa) is 10.59±0.10.[8] Thymol absorbs maximum UV radiation at 274 nm.[9]
History
The bee balms Monarda fistulosa and Monarda didyma, North American wildflowers, are natural sources of thymol. The Blackfoot Native Americans recognized these plants' strong antiseptic action and used poultices of the plants for skin infections and minor wounds. A tisane made from them was also used to treat mouth and throat infections caused by dental caries and gingivitis.[10]
Thymol was first isolated by German chemist Caspar Neumann in 1719.[11] In 1853, French chemist Alexandre Lallemand[12] (1816-1886) named thymol and determined its empirical formula.[13] Possible antiseptic properties of thymol were discovered in 1875,[14] and it was first synthesized by Swedish chemist Oskar Widman (1852-1930) in 1882.[15]
Extraction
The conventional method of extracting is hydro-distillation (HD), but can also be extracted with solvent-free microwave extraction (SFME). In 30 minutes, SFME yields similar amounts of thymol with more oxygenated compounds than 4.5 hours of hydro-distillation at atmospheric pressures without the need for solvent.[16]
Uses
During the 1910s, thymol was used for hookworm infection in the United States.[18][19] People of the Middle East continue to use za'atar, a delicacy made with large amounts of thyme, to reduce and eliminate internal parasites.[20] It is also used as a preservative in halothane, an anaesthetic, and as an antiseptic in mouthwash. When used to reduce plaque and gingivitis, thymol has been found to be more effective when used in combination with chlorhexidine than when used purely by itself.[21]
Thymol is a fragrance ingredient in some cosmetics.[4] Thymol has been used to successfully control varroa mites and prevent fermentation and the growth of mold in bee colonies.[22] Thymol is also used as a rapidly degrading, non-persisting pesticide,[4][23] such as insecticides and fungicides which are leveraged in plant care products. Thymol can also be used as a medical disinfectant and general purpose disinfectant.[24] Thymol is also used in the production of menthol through the hydrogenation of the aromatic ring.[25]
Thymol (and its isomer carvacrol) is commonly used to synthesize thymoquinone, a quinone derivative, through catalytic oxidation.[26][27]
List of plants that contain thymol
- Illicium verum[citation needed]
- Euphrasia rostkoviana[28]
- Lagoecia cuminoides[29]
- Monarda didyma[30]
- Monarda fistulosa[31]
- Mosla chinensis [citation needed]
- Ocimum gratissimum L.[32]
- Origanum compactum[33]
- Origanum dictamnus[34]
- Origanum onites[35][36]
- Origanum syriacum
- Origanum vulgare[37][38]
- Satureja hortensis
- Satureja thymbra
- Thymus glandulosus[33]
- Thymus hyemalis[39]
- Thymus serpyllum
- Thymus praecox
- Thymus vulgaris[39][40]
- Thymus zygis[41]
- Trachyspermum ammi
Toxicology and environmental impacts
In 2009, the U.S. Environmental Protection Agency (EPA) reviewed the research literature on the toxicology and environmental impact of thymol and concluded that "thymol has minimal potential toxicity and poses minimal risk".[42]
Environmental breakdown and use as a pesticide
Studies have shown that hydrocarbon monoterpenes and thymol in particular degrade rapidly (DT50 16 days in water, 5 days in soil[23]) in the environment and are, thus, low risks because of rapid dissipation and low bound residues,[23] supporting the use of thymol as a pesticide agent that offers a safe alternative to other more persistent chemical pesticides that can be dispersed in runoff and produce subsequent contamination. Though, there has been recent research into sustained released systems for botanically derived pesticides, such as using natural polysaccharides which would be biodegradable and biocompatible.[43]
Compendial status
See also
Notes and references
- ^ "Front Matter". Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book). Cambridge: The Royal Society of Chemistry. 2014. p. 691. doi:10.1039/9781849733069-FP001. ISBN 978-0-85404-182-4.
- ^ "Thymol". PubChem. Retrieved 1 April 2016.
- ^ Mndzhoyan AL (1940). "Thymol from Thymus kotschyanus". Sbornik Trudov Armyanskogo Filial. Akad. Nauk. 1940: 25–28.
- ^ a b c d e "Thymol". PubChem, US National Library of Medicine. 21 June 2025. Retrieved 28 June 2025.
- ^ O'Connell, John (27 August 2019). The book of spice: from anise to zedoary. New York: Pegasus. ISBN 978-1681774459. OCLC 959875923.
- ^ Stroh R, Sydel R, Hahn W (December 2012). Foerst W (ed.). Newer Methods of Preparative Organic Chemistry, Volume 2 (1st ed.). New York: Academic Press. p. 344. ISBN 9780323150422.
- ^ Fiege H, Voges HW, Hamamoto T, et al. (2000). "Phenol Derivatives". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a19_313. ISBN 3527306730.
- ^ CAS Registry: Data obtained from SciFinder[full citation needed]
- ^ Norwitz G, Nataro N, Keliher PN (1986). "Study of the Steam Distillation of Phenolic Compounds Using Ultraviolent Spectrometry". Anal. Chem. 58 (639–640): 641. doi:10.1021/ac00294a034.
- ^ Tilford GL (1997). Edible and Medicinal Plants of the West. Missoula, MT: Mountain Press Publishing. ISBN 978-0-87842-359-0.
- ^ Neuman C (1724). "De Camphora". Philosophical Transactions of the Royal Society of London. 33 (389): 321–332. doi:10.1098/rstl.1724.0061. On page 324, Neumann mentions that in 1719 he distilled some essential oils from various herbs. On page 326, he mentions that during these experiments, he obtained a crystalline substance from thyme oil, which he called "Camphora Thymi" (camphor of thyme). (Neumann gave the name "camphor" not only to the specific substance that today is called camphor but to any crystalline substance that precipitated from a volatile, fragrant oil from some plant.)
- ^ Marie-Étienne-Alexandre Lallemand (25 December 1816 – 16 March 1886)
- ^ Lallemand A (1853). "Sur la composition de l'huile essentielle de thym" [On the composition of the essential oil of thyme]. Comptes Rendus (in French). 37: 498–500.
- ^ Oettingen WF (1949). Phenol and Its Derivatives: The Relation Between Their Chemical Constitution and Their Effect on the Organism. U.S. Government Printing Office.
- ^ Widmann O (1882). "Ueber eine Synthese von Thymol aus Cuminol" [On a synthesis of thymol from cuminol]. Berichte der Deutschen Chemischen Gesellschaft zu Berlin (in German). 15: 166–172. doi:10.1002/cber.18820150139.
- ^ Lucchesi ME, Chemat F, Smadja J (23 July 2004). "Solvent-free microwave extraction of essential oil from aromatic herbs: comparison with conventional hydro-distillation". Journal of Chromatography A. 1043 (2): 323–327. doi:10.1016/j.chroma.2004.05.083. ISSN 0021-9673. PMID 15330107.
- ^ Krause ST, Liao P, Crocoll C, et al. (28 December 2021). "The biosynthesis of thymol, carvacrol, and thymohydroquinone in Lamiaceae proceeds via cytochrome P450s and a short-chain dehydrogenase". Proceedings of the National Academy of Sciences. 118 (52) e2110092118. Bibcode:2021PNAS..11810092K. doi:10.1073/pnas.2110092118. ISSN 0027-8424. PMC 8719858. PMID 34930840.
- ^ Ferrell JA (1914). The Rural School and Hookworm Disease. US Bureau of Education Bulletin. Vol. 20, Whole No. 593. Washington, DC: U.S. Government Printing Office.
- ^ Milton JR (1913). Preventive Medicine and Hygiene. D. Appleton. p. 119.
- ^ Inskeep S, Godoy M (11 June 2013). "Za'atar: A Spice Mix With Biblical Roots And Brain Food Reputation". NPR. Retrieved 24 February 2022.
- ^ Filoche SK, Soma K, Sissons CH (2005). "Antimicrobial effects of essential oils in combination with chlorhexidine digluconate". Oral Microbiol. Immunol. 20 (4): 221–225. doi:10.1111/j.1399-302X.2005.00216.x. PMID 15943766.
- ^ Ward M (8 March 2006). "Almond farmers seek healthy bees". BBC News. BBC.
- ^ a b c Hu D, Coats J (2008). "Evaluation of the environmental fate of thymol and phenethyl propionate in the laboratory". Pest Manag. Sci. 64 (7): 775–779. Bibcode:2008PMSci..64..775H. doi:10.1002/ps.1555. PMID 18381775.
- ^ "Thymol" (PDF). US Environmental Protection Agency. September 1993.
- ^ "Menthol | Definition, Structure, & Uses | Britannica". www.britannica.com. 6 October 2023. Retrieved 30 October 2023.
- ^ Günay T, Çimen Y, Karabacak RB, et al. (2016). "Oxidation of Thymol and Carvacrol to Thymoquinone with KHSO5 Catalyzed by Iron Phthalocyanine Tetrasulfonate in a Methanol–Water Mixture". Catalysis Letters. 146 (11): 2306–2312. doi:10.1007/s10562-016-1850-2. ISSN 1011-372X. Retrieved 22 February 2026.
- ^ Kani İ (2025). "Homogeneous catalytic oxidation of thymol with dinuclear Cu(II)-2-phenyl propionate-bipyridine complex". Polyhedron. 266 117312. doi:10.1016/j.poly.2024.117312. Retrieved 22 February 2026.
- ^ Novy P, Davidova H, Serrano Rojero CS, et al. (2015). "Composition and Antimicrobial Activity of Euphrasia rostkoviana Hayne Essential Oil". Evid Based Complement Alternat Med. 2015: 1–5. doi:10.1155/2015/734101. PMC 4427012. PMID 26000025.
- ^ Baser KH, Tümen G (1994). "Composition of the Essential Oil of Lagoecia cuminoides L. from Turkey". Journal of Essential Oil Research. 6 (5): 545–546. doi:10.1080/10412905.1994.9698448.
- ^ Donata Ricci, Francesco Epifano, Daniele Fraternale (February 2017). Olga Tzakou (ed.). "The Essential Oil of Monarda didyma L. (Lamiaceae) Exerts Phytotoxic Activity In Vitro against Various Weed Seeds". Molecules (Basel, Switzerland). 22 (2). Molecules: 222. doi:10.3390/molecules22020222. PMC 6155892. PMID 28157176.
- ^ Zamureenko VA, Klyuev NA, Bocharov BV, et al. (1989). "An investigation of the component composition of the essential oil of Monarda fistulosa". Chemistry of Natural Compounds. 25 (5): 549–551. Bibcode:1989CNatC..25..549Z. doi:10.1007/BF00598073. ISSN 1573-8388. S2CID 24267822.
- ^ Escobar A, Pérez M, Romanelli G, et al. (1 December 2020). "Thymol bioactivity: A review focusing on practical applications". Arabian Journal of Chemistry. 13 (12): 9243–9269. doi:10.1016/j.arabjc.2020.11.009. hdl:11336/139451. ISSN 1878-5352.
- ^ a b Bouchra C, Achouri M, Idrissi Hassani LM, et al. (2003). "Chemical composition and antifungal activity of essential oils of seven Moroccan Labiatae against Botrytis cinerea Pers: Fr". Journal of Ethnopharmacology. 89 (1): 165–169. doi:10.1016/S0378-8741(03)00275-7. PMID 14522450.
- ^ Liolios CC, Gortzi O, Lalas S, et al. (2009). "Liposomal incorporation of carvacrol and thymol isolated from the essential oil of Origanum dictamnus L. and in vitro antimicrobial activity". Food Chemistry. 112 (1): 77–83. doi:10.1016/j.foodchem.2008.05.060.
- ^ Ozkan G, Baydar H, Erbas S (2009). "The influence of harvest time on essential oil composition, phenolic constituents and antioxidant properties of Turkish oregano (Origanum onites L.)". Journal of the Science of Food and Agriculture. 90 (2): 205–209. doi:10.1002/jsfa.3788. PMID 20355032.
- ^ Lagouri V, Blekas G, Tsimidou M, et al. (1993). "Composition and antioxidant activity of essential oils from Oregano plants grown wild in Greece". Zeitschrift für Lebensmittel-Untersuchung und -Forschung A. 197 (1): 1431–4630. doi:10.1007/BF01202694. S2CID 81307357.
- ^ Kanias GD, Souleles C, Loukis A, et al. (1998). "Trace elements and essential oil composition in chemotypes of the aromatic plant Origanum vulgare". Journal of Radioanalytical and Nuclear Chemistry. 227 (1–2): 23–31. Bibcode:1998JRNC..227...23K. doi:10.1007/BF02386426. S2CID 94582250.
- ^ Figiel A, Szumny A, Gutiérrez Ortíz A, et al. (2010). "Composition of oregano essential oil (Origanum vulgare) as affected by drying method". Journal of Food Engineering. 98 (2): 240–247. doi:10.1016/j.jfoodeng.2010.01.002.
- ^ a b Goodner K, Mahattanatawee K, Plotto A, et al. (2006). "Aromatic profiles of Thymus hyemalis and Spanish T. vulgaris essential oils by GC–MS/GC–O". Industrial Crops and Products. 24 (3): 264–268. doi:10.1016/j.indcrop.2006.06.006.
- ^ Lee SJ, Umano K, Shibamoto T, et al. (2005). "Identification of volatile components in basil (Ocimum basilicum L.) and thyme leaves (Thymus vulgaris L.) and their antioxidant properties". Food Chemistry. 91 (1): 131–137. doi:10.1016/j.foodchem.2004.05.056.
- ^ Moldão Martins M, Palavra A, Beirão da Costa ML, et al. (2000). "Supercritical CO2 extraction of Thymus zygis L. subsp. sylvestris aroma". The Journal of Supercritical Fluids. 18 (1): 25–34. doi:10.1016/S0896-8446(00)00047-4.
- ^ 74 FR 12613
- ^ Campos EV, Proença PL, Oliveira JL, et al. (1 October 2019). "Use of botanical insecticides for sustainable agriculture: Future perspectives". Ecological Indicators. 105: 483–495. Bibcode:2019EcInd.105..483C. doi:10.1016/j.ecolind.2018.04.038. hdl:11449/179822. ISSN 1470-160X. S2CID 89798604.
- ^ The British Pharmacopoeia Secretariat (2009). "Index, BP 2009" (PDF). Archived from the original (PDF) on 11 April 2009. Retrieved 5 July 2009.
- ^ "Japanese Pharmacopoeia" (PDF). Archived from the original (PDF) on 22 July 2011. Retrieved 21 April 2010.
External links
Media related to Thymol at Wikimedia Commons
