Thiophene
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| General | |||||||||||||||||||
| Surname | Thiophene | ||||||||||||||||||
| other names |
Thiofuran |
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| Molecular formula | C 4 H 4 S | ||||||||||||||||||
| Brief description |
colorless liquid with a weak benzene odor |
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| properties | |||||||||||||||||||
| Molar mass | 84.14 g mol −1 | ||||||||||||||||||
| Physical state |
liquid |
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| density |
1.06 g cm −3 (20 ° C) |
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| Melting point |
−38 ° C |
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| boiling point |
84 ° C |
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| Vapor pressure |
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| solubility |
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| Dipole moment | |||||||||||||||||||
| Refractive index |
1.5289 |
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| Thermodynamic properties | |||||||||||||||||||
| ΔH f 0 |
80.2 kJ / mol |
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| As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . Refractive index: Na-D line , 20 ° C | |||||||||||||||||||
Thiophene , also called thiofuran , is an organic compound with the empirical formula C 4 H 4 S and is a heteroaromatic compound . Four carbon atoms and one sulfur atom form a five-membered ring with six π electrons , four come from the double bonds and two from a lone pair of electrons in sulfur.
If a thiophene ring occurs as a substituent , this is indicated with the prefix thienyl- . As Anelland , his name is Thieno .
history
Thiophene was discovered in 1883 by Victor Meyer in crude benzene, which was obtained by distilling coal tar . While “phen” should refer to the gaseous coke oven product “illuminating gas”, which at that time was used as town gas for lighting (Greek phainomei: to shine) in cities, “thio” is derived from sulfur (Greek theion, cf. also thioether ) .
The crude benzene used by Victor Meyer formed a blue dye with isatin when it was mixed with sulfuric acid ( indophenine reaction ). For this reason, the formation of indophenine was considered to be a reaction with benzene for a long time until an experiment with pure benzene did not result in a color reaction.
Hugo Erdmann and Jacob Volhard succeeded in synthesizing thiophene in the Volhard-Erdmann cyclization named after both .
Manufacturing
Technically, thiophene is synthesized from n -butane and sulfur at 560 ° C:
Instead of butane, derivatives of butane, such as butenes , butadiene or 1-butanol , can also be used as sulfur donors, for example sulfur dioxide or carbon disulfide .
Furthermore, thiophene can be obtained by heating sodium succinate with diphosphorus trisulfide or by passing acetylene over heated pyrite .
properties
Thiophene is at room temperature, a with water not miscible fluid , the benzene-like smell and at 84 ° C boiling .
Since it is an aromatic compound, its properties differ greatly from those of conventional thioethers : For example, it is not possible to alkylate sulfur using methyl iodide , while the CH groups flanking it are susceptible to electrophilic attack. Since it can be easily sulfonated with sulfuric acid , the conversion into the water-soluble thiophenesulfonic acid is the basis for the separation of thiophene from contaminated benzene. A separation of the benzene-thiophene mixture by distillation is hardly possible due to the boiling points which differ by only 4 ° C.
Safety-related parameters
Thiophene forms highly flammable vapor-air mixtures. The compound has a flash point of −9 ° C. The explosion range is between 1.5 vol.% (52 g / m 3 ) as the lower explosion limit (LEL) and 12.5 vol.% (435 g / m 3 ) as the upper explosion limit (UEL). The maximum explosion pressure is 8.4 bar. The limit gap width was determined to be 0.91 mm (50 ° C). This results in an assignment to explosion group IIA. The ignition temperature is 395 ° C. The substance therefore falls into temperature class T2.
Polythiophene
Polythiophenes (PT) can be produced by electrochemical polymerization of thiophene or its derivatives . It is also possible to produce 2,5-dihalothiophenes from Grignard compounds or by oxidation . Polythiophenes are extremely stable to heat, oxygen or moisture.
Undoped polythiophene has only a low conductivity . However, by doping with suitable oxidizing agents , conductivities of up to 100 S / cm can be achieved. Therefore, doped polythiophenes are used as electrode material , semiconductors and light emitters in organic light-emitting diodes . The polythiophenes glow when a voltage is applied, whereby the respective color can be varied with the electrical voltage. Since unsubstituted polythiophene is insoluble and infusible, PT derivatives are used for better processing.
Occurrence
Like benzene, thiophene is contained in coal tar and can also be contained in it as an impurity.
See also
- If the sulfur of the thiophene is formally replaced by oxygen , the structurally analogous compound furan is obtained .
- If you formally replace the sulfur atom with selenium , you get selenophene .
Web links
- Entry to thiophene . In: P. J. Linstrom, W. G. Mallard (Eds.): NIST Chemistry WebBook, NIST Standard Reference Database Number 69 . National Institute of Standards and Technology , Gaithersburg MD
Individual evidence
- ↑ a b c d e f g h i j k l m n o p Entry on thiophene in the GESTIS substance database of the IFA , accessed on February 20, 2018(JavaScript required) .
- ↑ a b c d e f g Entry on thiophene. In: Römpp Online . Georg Thieme Verlag, accessed on April 4, 2014.
- ↑ David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Dipole Moments, pp. 9-58.
- ↑ David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Standard Thermodynamic Properties of Chemical Substances, pp. 5-25.
- ↑ Victor Meyer: About the companion of benzene in coal tar
- ↑ Beyer-Walter Textbook of Organic Chemistry , 23rd edition, S. Hirzel Verlag 1998.
- ↑ a b c d e f E. Brandes, W. Möller: Safety-related parameters. Volume 1: Flammable Liquids and Gases. Wirtschaftsverlag NW - Verlag für neue Wissenschaft, Bremerhaven 2003.