To prepare and submit Sulphanilamide from acetanilide – Practical Medicinal Chemistry

 Aim: To prepare and submit Sulphanilamide from acetanilide.

Requirements: Beaker, funnel, conical flask, Buchner funnel, acetanilide, chlorosulphonic acid, aqueous ammonia.

Theory: For the preparation of sulphanilamide, acetanilide is treated with chlorosulphonic acid, which forms p-acetamidobenzene sulphonyl chloride, which on treatment with ammonia gives p-acetamidobenzene sulphonamide, followed by hydrolysis.

Reactions involved:

Step-I: Synthesis of p-acetamido benzene sulphonyl chloride:

Step-II: Synthesis of p-acetamido benzene sulphonamide:

Step-III: Synthesis of Sulphanilamide:


Step 1: Synthesis of p-acetamidobenzene sulphonyl chloride:

  • Take 25 g powdered acetanilide in a two mouth round bottom flask fitted with dropping funnel and reflux condenser.
  • From dropping funnel, add 63 ml chlorosulphonic acid drop by drop to it with frequent shaking.
  • Fix a calcium chloride guard tube to it. Heat the content to 60-70°C for about 2 hours.
  • Cool the mixture and pour it in crushed ice, where p-acetamidobenzene sulphonyl chloride separated out.
  • Filter the product and wash with cold water and dried.

Step 2: Synthesis of p-acetamidobenzene sulphonamide:

  • Take all p-acetamidobenzene sulphonyl chloride in a 500 ml round bottom flask
  • Add 120 ml of concentrated ammonia and 120 ml water to it with shaking.
  • Heat the mixture at 70°C for 30 minutes.
  • Cool the mixture in ice bath and acidify the reaction mixture with dilute sulphuric acid.
  • Filter the precipitated p-acetamidobenzene sulphonamide, wash with cold water and dry at 100°C in oven.

Step 3: Synthesis of sulphanilamide:

  • Add all p-acetamidobenzene sulphonamide to a mixture of 10 ml conc. hydrochloric acid and 30 ml distilled water in 250 ml round bottom flask
  • Boil the mixture for 1 hour.
  • No solid separates on cooling. If a solid separates, heat further for a short period.
  • Add 1 g charcoal to solution (for decolourize the solution), boil for 15 minutes and filter.
  • To the filtrate add 6 g solid sodium carbonate slowly and installments with stirring until no more effervescences are observed.
  • Cool the solution in ice bath, and then sulphanilamide precipitates out.
  • Filter the product in Buchner funnel with suction and dry.
  • Recrystallize with water or alcohol.
  • The melting point of sulphanilamide is 163°C.

Results: The yield of obtained product was found to be ___ gm and percentage yield was ___% and melting point was found to be ___°C.

Theoretical yield =

Practical yield =

Practical yield = (Percentage of yield/Theoretical yield) x 100

Uses: Sulphanilamide is used as an antibacterial, antifungal drug and for the treatment of vaginal yeast infections.

Cautions: Glass ware should be clean and dry before being used. Use chlorosulphonic acid very carefully. It is very corrosive to the skin and to clothing and reacts with water with violence. Use chemicals only in the hood and be sure the hood exhaust fan is on.

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