Acetaminobenzene Sulfonyl Chloride

In a 500 cc. round-bottom flask, fitted with a mechanical stirrer, is placed 290 g. (2.49 moles) of chlorosulfonic acid (Note 1). The flask is surrounded by a cooling bath and cooled with running water to about 12-150. To the chlorosulfonic acid is added gradually 67.5 g. (0.5 moles) of acetanilide. This requires about fifteen minutes if the temperature is maintained at approxi mately 15°. Since large volumes of hydrogen chloride are evolved, the reaction should be conducted in a good hood. After all of the acetanilide has been added, the mixture is heated to 6o° for two hours to complete the reaction (Note 2). 

The syrupy liquid is poured slowly, with stirring (Note 3), into 1 kg. of ice to which just enough water has been added to make stirring easy. This decomposition of the excess chlorosulfonic acid should be carried out in the hood. The solid sul-fonyl chloride which separates is collected on a suction funnel (Note 4) and washed with water. The yield of crude material is 90-95 g. (77-81 per cent of the theoretical amount based on the acetanilide). 

This crude material may be used directly in many preparations such as -acetaminobenzene sulfinic acid (p. 1). If a pure product is desired, the crude material is dried by pressing on a porous plate and then crystallized from dry benzene. The acid 

The chlorosulfonic acid should be freshly distilled. Smaller amounts of this reagent may be used without reducing the yield or affecting the quality of the product. However, with smaller amounts the time required for the reaction must be increased. Thus, if 175 g. of chlorosulfonic acid is used with 67.5 g. of acetanilide, an additional hour of heating is required to obtain the yields mentioned above. 

The hydrogen chloride which is liberated during the reaction fills the mixture with tiny bubbles. When these disappear the reaction is complete. 

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The crude -acetaminobenzene sulfonyl chloride (p. 3) obtained from 67.5 g. (0.5 mole) of acetanilide is shaken for two hours with a solution of 250 g. (1 mole) of crystallized sodium sulfite (Na2S03 7H2O) in 500 cc. of water. The reaction mixture is kept slightly alkaline by the addition at intervals of small portions of 50 per cent sodium hydroxide solution. The total volume of alkali used varies from 10 to 50 cc. After the alkaline mixture has been shaken for the two-hour period (Note 1) it is filtered, and the filtrate is acidified with 60 per cent sulfuric acid. If the acid is added slowly, the sulfinic acid comes down in fine crystals which after filtering and drying, melt at 1550 with decomposition (Note 2). The yield is 50-55 g. (43-47 per cent of the theoretical amount based on the acetanilide used). 

Acetaminobenzene suliinic acid has been prepared only by the reduction of -acetaminobenzene sulfonyl chloride.1... 

Acetaminobenzene sulfonyl chloride has been prepared by the action of phosphorus pentachloride on sodium / -acetamino-benzene sulfonate1 and by the action of chlorosulfonic acid on acetanilide.2... 

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