METHOD FOR PRODUCING THIOPHENE-2 Russian patent published in 1997 - IPC

5-DICARBOXYLIC ACID. FIELD: chemical engineering, specifically, preparation of thiophene-2.5-dicarboxylic acid used, as starting product, for producing optical-grade bleachers of polymers, and for producing polyester and polyamide fibres and plastics. SUBSTANCE: thiophene-2.5-dicarboxylic acid is produced by chloromethylation of thiophene contained in thiophene/benzene fraction resulting from coking process, with mixture of formalin and concentrated hydrochloric acid saturated with hydrogen chloride gas to thereby produce 2.5-di(chloromethyl)thiophene. The latter is subjected to acetolysis by reacting with alkali metal acetate to produce 2.5-di(acetoxymethyl)-thiophene which is subjected to alkaline hydrolysis to obtain 2.5-di(hydroxymethyl)thiophene. The latter is oxidized with potassium permanganate or nitric acid to desired product. For sake of simplicity, entire process is carried out without isolating and purifying all intermediates. Starting thiophene/benzene fraction resulting from coking process has following composition, wt.%: thiphene 28-86.7; benzene 6-66.0; toluene 0.7-7.4; alicyclic and aliphatic hydrocarbons (cyclohexane, hexane, heptane, etc.), the balance. Said fraction contains no non-limiting hydrocarbons. EFFECT: method uses relatively easily available and cheap starting material, namely, thiphene/benzene fraction of coking process instead of short-supply pure thiophene, as before; production is simpler and cheaper. 2 cl