PREPARATION OF SULFANILAMIDE
REQUIREMENTS
ü Acetanilide
ü Chlorosulphonic acid
ü Concentrated ammonia solution
ü Dilute sulfuric acid
ü Decolourising carbon
ü Solid sodium bi carbonate
ü alcohol
PRINCIPLE
p-acetamido benzene sulfonyl chloride is an essentialintermediate for the synthesis of sulfanilamide drugs. Chlorosulfonation of acetanilide with excess of chlorosulfonic acid affords p-acetamido benzene sulfonyl chloride. Aryl sulfonyl chlorides are converted into corresponding aryl sulfonamides by treatment with conc. ammonia solution or solid ammonium carbonate or by reaction with appropriateamino compounds .p- amino benzene sulfonamide is obtained by converting p-acetamido benzene sulfonyl chloride into the amide with aqueous ammonia and then selectively removing the protecting acetyl group by boiling with aqueous hydrochloric acid.
PROCEDURE (All apparatus must be perfectly dry,chlorosulfonic acid reacts violently with water)
ü Preparation of p-acetamido benzene sulfonyl chloride
Place 5 gm of dry acetanilide into a three necked flaskequipped with a condenser, add 16 ml of chlorosulfonic acid slowly in small portions. Shake the flask well and heat theflask on a water bath for 1 hr .Cool and pour this oily mixtureas a thin stream with stirring into 100 gm of crushed ice. Rinse with water and broke the ice lumps and stir the mixture for several minutes. Filter it at the pump, wash it with cold waterand drain well.
ü Preparation of p-acetamido benzene sulphonamide
Transfer the crude product obtained above into a round bottomflask. Add a mixture of 15ml of ammonia and 15ml of water. Mix the contents of the flask thoroughly with swirling. Heat themixture for 15 mins (below boiling point.). The sulphonyl chloride is converted into corresponding sulfonamide. Cool on ice, add dil. sulphuric acid until the mixture was just acidic to congo red paper. Collected the product in a buchner funnel.
ü Preparation of p-amino benzene sulphonamide.
Transfer the crude product into 500ml flask and add 5ml of conc. HCl, 10ml of water. Boil the mixture gently under refluxfor 10-30 minutes. Cool the mixture to room temperature(should not show any solid) to this add 3gm of charcoal, heat the mixture to boil. Place the filtrate in beaker and continuously add 4gm of solid sodium bicarbonate. Test the filtrate with litmus paper until neutral. Cool it in ice bath and filter the precipitate. Recrystallize from water or alcohol.
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