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thiophene

Product name thiophene
Synonyms thiofuran
GOST no data
CAS 110-02-1

Thiohene is a clear, colorless, flammable liquid with a benzene like odor. It is fully miscible with benzene, toluene, hexane, diethyl ether, ethanol, carbon tetrachloride and many other organic solvents; almost insoluble in water. Thiophene molecule has a practically planar geometry.

Thiohene was accidentally discovered in 1882 by German chemist V. Meyer as an admixture in crude benzene, obtained from coal tar. Thiophene shows well-defined aromatic properties. Being compared with analogs, its aromaticity is in order of benzene > thiophene > pyrrole > furan. Almost specialists suggest that sulfur d-orbitals does not practically affect on thiophene properties in a ground state.

Chemical properties of thiopene are typical for aromatic compounds, but due to its π-excess aromatic system the reactivity is greater. Thus, in electrophilic substitution reactions (halogenation, nitration, deuteration, formylation, sulfination and others) the reaction rates are in 600-100000 times as much as benzene ones. Reaction proceeds to give presumably (sometimes only) 2-substitution adduct. Direct bromination of thiophene results in 2-bromothiophene.

Metallation is the way to rich many thiophene derivatives. Metallated thiophene derivatives are produced by interaction with corresponding organometallic compounds. Most common is 2-lithiothiothene or 2-thienyllithium is produced by interaction with n-butyllithium. Magnesium-, mercury- and sodium- derivatives can be obtained by treatment of thiophene with proper organometallic compounds. In these reaction thiophene behaves as CH-acid, process proceeds fast, quantitatively and with an excellent regioselectivity to form 2-substituted product:

interaction of thiophene with butyllithium

Production.

Industrially thiophene is produced from two sources:

  • By processing of pyrolysis fractions of coal, shale oil or sulfurous oils. So-called crude benzene which is obtained from coal tar containes 1.3-1.4% of thiophene. Some shale oil pyrolysis fractions contain it up to 70%.
  • Synthetic method for thiophene and its homologues production were first patented by American company Socony-Vakuum in the middle of 1940s and then developed by British company Croda Synthetic Chemicals. The process is based on interaction of four-carbon fragment with sulfur source in the presence of catalyst (aluminum oxides or silica gel doped with transition metal oxides). Butane, butylene, butadiene or its derivatives such as alcohols, aldehydes, ketones or furan can be used as four-carbon fragment. Sulfur containing reactant is used in different forms such as elemental sulfur, carbon disulfide, dihydrogen sulfide, sulfur oxides, metal sulfides. The temperature of reaction depends on reactants and catalysts and varies in the range from 180°C to 700°C.

Uses.

Thiopene is used as a starting material for numerous derivatives syntheses.

  • pharmaceuticals and bioactive compounds such as antihelminth drugs, antibiotics;
  • for preparation of optical bleaching agents (2,5-thiophenecarboxylic acid);
  • monomers for electroconducting polymers syntheses;

Manufacturer(s) no data
Chemical structure of thiophene

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