Thymol

Structural formula
General
Surname	Thymol
other names	2-isopropyl-5-methyl-phenol; 2- (1-methylethyl) -5-methyl-phenol; THYMOL ( INCI ) ;
Molecular formula	C 10 H 14 O
Brief description	colorless, spicy thyme-smelling, burning-tasting plates
External identifiers / databases
EC number	201-944-8
ECHA InfoCard	100,001,768
PubChem	6989
ChemSpider	21105998
DrugBank	DB02513
Wikidata	Q408883
properties
Molar mass	150.22 g mol −1
Physical state	firmly
density	0.97 g cm −3 (20 ° C)
Melting point	49-51 ° C
boiling point	233 ° C
Vapor pressure	2.5 hPa (50 ° C)
solubility	poor in water (0.98 g l −1 at 25 ° C) and glycerine ; good in caustic soda , ethanol , diethyl ether , carbon disulfide and chloroform ;
safety instructions
H and P phrases	H: 302-314-411
	P: 273-280-303 + 361 + 353-304 + 340 + 310-305 + 351 + 338-391
Toxicological data	980 mg kg −1 ( LD 50 , rat , oral )
	As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

The thymol is a terpenoid natural products . The systematic name ( IUPAC ) of thymol is 2- (1-methylethyl) -5-methyl-phenol. The compound represents a structural isomer ( constitutional isomer ) to carvacrol .

History and occurrence

Thyme ( Thymus vulgaris )

In addition to its isomer carvacrol, thymol is a component of the essential oils from ajwain , thyme , oregano and savory .

In ancient Egypt , thymol and carvacrol were used in the form of thyme preparations to preserve mummies because of their bactericidal and fungicidal properties .

The crystalline substance thymol was discovered by Kaspar Neumann in 1719 and presented in pure form by M. Lallemand in 1842 and characterized by an elemental analysis . This enabled him to determine the correct ratio of the elements carbon , hydrogen and oxygen that make up this substance. Also keep Ferdinand Runge worked on the chemistry of this substance. The crystal structure analysis with the exact determination of the atomic positions was published by Alain Thozet and M. Perrin in 1980 .

Extraction and presentation

Thymol can via the reaction of m - cresol and propene in the presence of acidic catalysts, such as. B. zeolites .

properties

Thymol, crystalline, e.g. T. powder-coated on a watch glass bowl

The solid melts at 49-51 ° C and boils at 233 ° C. The density is 0.97 g / cm³. The vapor pressure is 2.5 hPa at 50 ° C. According to Antoine, the vapor pressure function results from log ₁₀ (P) = A− (B / (T + C)) (P in bar, T in K) with A = 5, 29395, B = 2522.332 and C = −28.5756 in the temperature range from 337.5 to 505.0 K. Thymol forms flammable vapor-air mixtures above the flash point temperature. The compound has a flash point of 104 ° C. The ignition temperature is approx. 285 ° C. The substance therefore falls into temperature class T3.

Since thymol is a phenol derivative , it shows the typical behavior of phenol. This means that it dissolves in caustic soda or potassium hydroxide and is released again through acidification. It is also readily soluble in ethanol , ether and chloroform: 1000 g of thymol dissolve in one liter of ethanol at 25 ° C, and around 1428 g of thymol in one liter of chloroform. It is only sparingly soluble in water; about one gram of thymol dissolves in one liter of water.

Thymol results in a color reaction in water with iron (III) chloride through the formation of a complex, but this is not visible to the eye due to the low solubility of thymol. However, after adding ethanol , the complex is visible as a green color.

Thymol can be hydrogenated to menthol .

The bromination of thymol with elemental bromine in acetic acid leads exclusively to 4-bromothymol .

use

Thymol is characterized by a strong disinfectant, fungicidal and bactericidal effect and, because of its pleasant taste, is used in mouthwashes, toothpaste and in alcoholic solution for skin disinfection or locally against skin fungi, for example as a component of vaginal capsules or for the treatment of oral cavity fungus in AIDS - Patient. In veterinary medicine, thymol has also been used for many years to treat skin fungal infections, but also as a digestive aid. In bee care, thymol is used as an active ingredient against mite infestation (varroosis).

Thymol can also be used to store and preserve extracted teeth before further processing for scientific study purposes.

The triphenylmethane dyes thymolphthalein , thymol blue and bromothymol blue , which are used as pH indicators, are derived from thymol .

Individual evidence

↑ Entry on THYMOL in the CosIng database of the EU Commission, accessed on May 11, 2020.
↑ ^a ^b ^c Entry on thymol. In: Römpp Online . Georg Thieme Verlag, accessed on September 30, 2014.
↑ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k ^l Entry on thymol in the GESTIS substance database of the IFA , accessed on January 10, 2017(JavaScript required) .
↑ Entry on thymol in the Classification and Labeling Inventory of the European Chemicals Agency (ECHA), accessed on February 1, 2016. Manufacturers or distributors can expand the harmonized classification and labeling .
↑ Patent for the synthesis of thymol .
^ Stull, DR: Vapor Pressure of Pure Substances. Organic and Inorganic Compounds , in: Ind. Eng. Chem. , 1947 , 39 , pp. 517-540 ( doi : 10.1021 / ie50448a022 ).
↑ Abstracts of Chemical Papers, Preparation of Parabromothymol, J. Chem. Soc. , 1894 , 66 (1), p. 19 ( full text ).
↑ Heinz Lüllmann, Klaus Mohr, Lutz Hein: Pharmakologie und Toxikologie , Georg Thieme, Stuttgart, 2010, p. 451 ( limited preview in the Google book search).
↑ Jochen Peter Baumeister: Microradiographic studies on the influence of different storage media and polishing on the in vitro de- and remineralization of bovine and human enamel . (PDF; 3.5 MB) Zahnmed. Dissertation, Berlin 2011.

Web links

Commons : Thymol - collection of images, videos and audio files

About the discovery of thymol sensor cells in the gastrointestinal tract , June 12, 2007.

[CosIng-1] Entry on THYMOL in the CosIng database of the EU Commission, accessed on May 11, 2020.

[roempp-2] Entry on thymol. In: Römpp Online . Georg Thieme Verlag, accessed on September 30, 2014.

[GESTIS-3] ↑ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k ^l Entry on thymol in the GESTIS substance database of the IFA , accessed on January 10, 2017(JavaScript required) .

[CLP_100.001.768-4] Entry on thymol in the Classification and Labeling Inventory of the European Chemicals Agency (ECHA), accessed on February 1, 2016. Manufacturers or distributors can expand the harmonized classification and labeling .

[5] Patent for the synthesis of thymol .

[6] Stull, DR: Vapor Pressure of Pure Substances. Organic and Inorganic Compounds , in: Ind. Eng. Chem. , 1947 , 39 , pp. 517-540 ( doi : 10.1021 / ie50448a022 ).

[JCS-7] Abstracts of Chemical Papers, Preparation of Parabromothymol, J. Chem. Soc. , 1894 , 66 (1), p. 19 ( full text ).

[8] Heinz Lüllmann, Klaus Mohr, Lutz Hein: Pharmakologie und Toxikologie , Georg Thieme, Stuttgart, 2010, p. 451 ( limited preview in the Google book search).

[9] Jochen Peter Baumeister: Microradiographic studies on the influence of different storage media and polishing on the in vitro de- and remineralization of bovine and human enamel . (PDF; 3.5 MB) Zahnmed. Dissertation, Berlin 2011.