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温度

0 °C

In a glass autoclave, 8.6 g. of 4-chlorothiophene-3-carboxylic acid are dissolved in 23 ml. of water containing 2.1 g. of sodium hydroxide, whereupon a solution of 5.6 g. of sodium bisulfite in 16 ml. of water is added and the solution make just alkaline with a 30% sodium hydroxide solution. The solution is treated with 0.43 g. of copper (I) chloride and heated at 143° C. for 16 hours. After cooling, the red copper oxide is filtered off under suction. The filtrate is acidified with 7 ml. of concentrated hydrochloric acid and the unreacted starting material precipitates out, the latter being removed by shaking out with ether. The acidic solution is treated with 12 g. of potassium chloride while warming and, after cooling to 0° C, the potassium salt of 4-sulfothiophene-3-carboxylic acid separates as colorless crystals. The crystals are dissolved in 50 ml. of water and the solution passed through an ion-exchange column which is charged with protons, after which the column is rinsed with water until the solution flowing out has a pH value of 5. The eluate is evaporated to dryness in vacuo. There is obtained 4-sulfothiophene-3-carboxylic acid as a crystalline residue of melting point 154° C (recrystallization from water).

1. additionThe solution is treated with 0.43 g
2. temperatureAfter cooling
3. filtrationthe red copper oxide is filtered off under suction
4. customprecipitates out
5. customthe latter being removed
6. additionThe acidic solution is treated with 12 g
7. temperatureof potassium chloride while warming
8. dissolutionThe crystals are dissolved in 50 ml
9. additionis charged with protons
10. washafter which the column is rinsed with water until the solution
11. customThe eluate is evaporated to dryness in vacuo