Synthesis of sulphanilamide from acetanilide

Rate this post

[ps2id id=’background’ target=”/]

BACKGROUND

Principle:

Sulphanilamide can beprepared by taking acetanilide and treating it with excess of chlorosulphonic acid, which gives p-acetamidobenzenesulphonyl chloride which readily converted into corresponding p-acetamidobenzenesulphonamides upon reaction with ammonia or ammonium carbonate. The acetamido groups can easily undergo acid catalyzed hydrolysis reaction to form p-aminobenzene sulphonamide (sulphanilamide).1

Aim:

To prepare sulphanilamide from acetanilide.

Reactions:

Step 1:


Step 2:


Step 3:


Use: It is used as bacteriostatic agent.

[ps2id id=’requirements’ target=”/]

REQUIREMENTS

Chemicals:     Acetanilide

Chlorosulphonic acid

Conc. ammonia

Dilute sulphuric acid

Sodium bicarbonate

Concentrated hydrochloric acid

Apparatus:     Round-bottom flask – 2000 ml

Reflux condenser

Beaker

Buchner funnel

Measuring cylinder

Filter paper

[ps2id id=’procedure’ target=”/]

PROCEDURE

Step 1: To prepare p-acetamidobenzenesulphonyl chloride

Equip a double necked 500 ml flask with a dropping funnel and a reflux condenser. Attach the top of the latter to a device for the absorption of hydrogen chloride. Take 20 g (0.148 mol) of dry acetanilide in the flask and a good grade chlorosulphonic acid, 50 ml (90 g, 0.77 mol) in the dropping funnel and attach a calcium chloride guard tube into the latter. Add the chlorosulphonic acid in small portions and shake the flask from time to time to ensure thorough mixing. Heat the reaction mixture on a water bath for 1 h after mixing in order to complete the reaction. Keep some time for cooling and then pour the oily mixture in a thin stream with stirring into 300 g of crushed ice (or ice water) contained in a 1 litre beaker. Carry out this operation carefully in the fume cupboard since the excess of chlorosulphonic acid reacts vigorously with the water. Rinse the flask with a little ice water and add the contents after rinsing to the contents of the beaker. Break up the lumps (if any) of solid material and mix the content by stirring for several min in order to obtain an even suspension of the granular white solid. Filter off the p-acetamidobenzenesulphonyl chloride at the pump and wash it with a little cold water; press and drain well. Use the crude product immediately in the next stage.

Step 2: To prepare p-acetamidobenzenesulphonamide:

Transfer the crude p-acetamidobenzenesulphonyl chloride to the rinsed reaction flask and add a mixture of 70 ml of concentrated ammonia solution and 70 ml of water. Mix well the contents of the flask and heat the reaction mixture with occasional swirling (fume cupboard) to just below the boiling point for about 15 min the sulphonyl chloride will be converted into a pasty suspension of the corresponding sulphonamide. Cool the product suspension in ice, and then add dilute sulphuric acid until the mixture is just acid to congo red paper. collect the product on a buchner funnel, wash with a little cold water and drain as completely as possible. it is desirable, but not essential, to dry the crude pacetamidobenzenesulphonamide at 100 °C: the yield is about 18 g. The material is sufficiently pure for the next stage.

Step 3: To prepare p-aminobenzenesulphonamide

Transfer the crude p-acetamidobenzenesulphonamide to a 500 ml flask, mix 10 ml of concentrated hydrochloric acid 30 ml of water. Boil the mixture gently under reflux for 30-45 min. Then cool the solution to room temperature, should deposit no solid amide; if a solid separates, heat for a further short period. Treat the cooled solution with 2 g of decolourising carbon, heat the mixture to boiling and filter with suction through a hardened filter paper. Place the filtrate of the mixture (a solution of sulphanilamide hydrochloride) in a one litre beaker and carefully add 16 g of solid sodium hydrogen carbonate in some portions with constant stirring. After the evolution of gas has subsided, test the suspension with litmus paper and if it is still acid, add more sodium hydrogen carbonate until neutral. Cool in ice, filter off the sulphanilamide with suction and dry. The yield is 15 g (59% overall yield), m.p. 161-163 °C. A pure product, m.p. 163-164 °C, may be obtained by recrystallisation from water or from alcohol.

Calculation:

Here limiting reagent is acetanilide; hence yield shou+ld be calculated from its amount taken.

Molecular formula of acetanilide = C8H9NO

Molecular formula of sulphanilamide = C6H8N2O2S

Molecular weight of acetanilide = 135 g/mole

Molecular weight of sulphanilamide = 172 g/mole

Theoretical yield:

135 g acetanilide forms 172 g sulphanilamide

Therefore, 20 g acetanilide will form …….? (X) g sulphanilamide

X =(172 ×20)/135 = 25.48 g

Theoretical yield = 25.48 g

Practical yield = ————- g

% Yield = (Practical Yield)/(Theoretical Yield) × 100

[ps2id id=’conclusion’ target=”/]

CONCLUSION

Sulphanilamide was synthesized and the percentage yield was found to be………..%

[ps2id id=’references’ target=”/][ps2id id=’1′ target=”/]

REFERENCES

  1. Vogel’s Textbook of Practical Organic Chemistry by Brian S. Furniss, Antony J. Hannaford, Peter W. G. Smith & Austin R. Tatchell; Fifth Edition; Page No. 883.
  2. Practical in organic chemistry, by Hitesh G. Raval, Sunil L. Baldania and Dimal A. Shah, Nirav Prakashan, Page No. 308.