Thiophene removal from benzene

Commercial benzene may contain thiophene C H S, b.p. 84°, which cannot be separated by distillation or by fractional crystallisation. The presence of thiophene may be detected by shaking 3 ml. of benzene with a solution of 10 mg. of isatin in 10 ml. of concentrated sulphuric acid and allowing the mixture to stand for a short time a bluish-green colouration is produced if thiophene is present. The thiophene may be removed from benzene by any of the following methods —... 

In a commercially useful reaction, sulfuric acid can be used to sulfonate thiophene at room temperature Benzene is not attacked under these conditions, and needs a reaction with oleum at 60 °C before it is sulfonated. Thiophene-2-sulfonic acid, formed in this way, dissolves in dilute alkali, allowing thiophene in coal tar distillate to be easily removed from benzene. Thiophene can be generated from its sulfonic acid by heating the latter in steam. 

THTOPHENE. [CAS 110-02-1]. (CH C.H)2)S, formula weight 84.H, colorless liquid resembling benzene in odor, mp —30°C, bp 84°C. sp gr 1,070. Thiophene and its derivatives closely resemble benzene and its derivatives in physical ancl chemical properties. Thiophene is present in coal tar and is recovered in the benzene distillation fraction (up to about 0.5% of the benzene present). Its removal from benzene is accomplished by mixing with concentrated sulfuric acid, soluble thiophene sulfonic acid being formed. Thiophene gives a characteristic blue coloration with isatin in concentrated sulfuric add. 

Weitkamp, J. Schwaik, M. Emest, S. Removal of Thiophene Impurities from Benzene by Selective Adsorption in Zeolite ZSM-5. J. Chem. Soc. Chem. Commun., 1991, 1133. 

Thiophene has been removed from benzene (absence of bluish-green coloration when 3mL of benzene is shaken with a solution of lOmg of isatin in lOmL of cone H2SO4) by refluxing the benzene (1.25L) for several hours with 40g HgO (freshly precipitated) dissolved in 40mL glacial acetic acid and 300mL of water. The precipitate is filtered off, the aqueous phase is removed and the benzene is washed twice with H2O, dried and... 

Thiophene has been removed from benzene (absence of a bluish-green coloration when 3ml of benzene is... 

For the determination of nitrate, use a 1 dram vial with a polyethylene stopper (Kimble No. 60975-L) as a reaction vessel. Introduce a 0.20ml aliquot of aqueous sample into the vial, followed by 1.0ml of thiophen free benzene. Catalyse the reaction by addition of 1.0ml of concentrated sulphuric acid. Shake the vial for lOmin. Remove the benzene layer immediately from the reaction vial with a Pasteur pipette, place it in a separate vial and analyse by gas chromatography with electron capture detection for the nitrobenzene concentration generated. Treat standard solutions of potassium nitrate in the same manner to generate a standard calibration plot relating nitrobenzene concentration to peak height. If higher precision is desired (approximately 4% relative standard deviation), add 2,5-dimethylnitrobenzene to the benzene prior to reaction. 

Raney nickel acts to remove sulfur from organic compounds even in the cold (119,120). The use of Raney nickel for the removal of thiophene from benzene and methylthiophene from toluene has also been reported. 

S, From benzene. A mixture of 50 grams of mercuric acetate, 50 c.c. of glacial acetic acid, and 100 c.c. of thiophene-free benzene is heated in a pressure flask for five hours at 100° C., then cooled, the residue filtered off and washed several times with benzene. The filtrate which contains the acetate is evaporated down and treated with alcoholic calcium chloride solution, when the chloride is precipitated. This is filtered off and washed with hot water to remove any adhering calcium chloride. 

A solution of 200 mg (0.89 mmol) of (1 /J,S )-l-(1-phenylethoxy)-1,3-dihydrobenzo[c]thiophene-2,2-dioxide (I5a), 349 mg (3.56 mmol) of maleic anhydride (22) and 30 mg of powdered ZnO in 10 mL of benzene is refluxed for 20 h. The solution is filtered to remove ZnO, evaporated, and then heated to 100 CC under high vacuum to remove the maleic anhydride. The residue is recrystallized from benzene/hexane to give the major diastereomer as colorless crystals yield 286 mg (100%). 

Removal of thiophen from benzene 2 Benzene (11) is stirred with concentrated sulfuric acid (80 ml) for 1.5 h at room temperature. The sulfuric acid is separated and these operations... 

Multi-site reactions are important in heterogeneous catalysis, and it is likely that more than one metal center is needed to effect sulfur removal from organic molecules. Therefore, binuclear or polynuclear metal complexes are of interest in modeling HDS reactions in solution. Thiophenes interact with Fe3(CO)i2 in refluxing benzene to produce thiaferroles 30 through metal insertion into the less hindered G-S bond of the thiophene. The... 

Multiple substitution of reactive aromatic compounds may occur. Thiophene gives a 2, 5-disubstituted and furan a 2,3,4, 5-tetrasubstituted derivative with mercury (II) acetate in boiling ethanol. The preferential mercuration of thiophene has been used for its removal from commercial benzene. Mercuration of ferrocene (p. 284) also occurs readily. 

The preferential mercuration of thiophene provides a good method for its removal from commercial benzene. 

An early process for the separation of thiophene from benzene reste on the fact that this compound condenses more rapidly w ith acid formalde-hA de than does benzene. According to this pi ocedure, 10,000 parts of benzene containing thiophene ai e agitated with 1500 parts of 73 per cent sulfuric acid and 45 parts of 30 per cent formaldehyde at ordinary temperature for several hours. When the benzene layer ceases to give a test for thiophene, it is removed from the acid liquor and steam-distilled to separate it from amorphous condensates ... 

By treatment with anhydrous aluminium chloride (Holmes and Beeman, 1934). Ordinary commercial, water-white benzene contains about 0 05 per cent, of thiophene. It is first dried with anhydrous calcium chloride. One litre of the dry crude benzene is shaken vigorously (preferably in a mechanical shaking machine) with 12 g. of anhydrous aluminium chloride for half an hour the temperature should preferably be 25-35°. The benzene is then decanted from the red liquid formed, washed with 10 per cent, sodium hydroxide solution (to remove soluble sulphur compounds), then with water, and finally dried over anhydrous calcium chloride. It is then distilled and the fraction, b.p. 79-5-80-5°, is collected. The latter is again vigorously shaken with 24 g. of anhydrous aluminium chloride for 30 minutes, decanted from the red liquid, washed with 10 per cent, sodium hydroxide solution, water, dried, and distilled. The resulting benzene is free from thiophene. 

About 1 gram of sodamide in fine powder is washed several times vrith benzene and placed in a 200 c.c. fiask. About 50 c.c. of benzene, free from thiophene, is added, and the fiask, attached to a condenser, warmed on the water-bath, and traces of ammonia are removed by a stream of carbon dioxide. From 1 to 2 grams of the phenol-containing oil is then admitted to the fiask through a stoppered funnel inserted through the... 

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