To prepares a pure sample of Para Bromo-acetanilide from acetanilide.

To prepares a pure sample of Para Bromo-acetanilide from acetanilide.

 Theory:

Para-bromoacetanildie can be prepared by the action of bromine dissolved in glacial acetic acid on acetanilide.

C₆H₅NHCOCH₃ + Br₂ →Br-C₆H₄-NHCOCH₃ + HBr

 P-Bromo acetanilide is the main product (80%) and ortho Bromoacetanilide is formed in small quantity (20 %). Since ortho isomer is more soluble in ethyl alcohol it can be easily removed by crystallization from ethyl alcohol.

Requirements: 

(a) Apparatus :

250 ml conical flask, separating funnel. Buchner funnel, filtration flask, and suction pump.

(b) Chemicals :

 (i) Acetanilide = 8.0 g

(ii) Glacial acetic acid = 28.0 ml.

(iii) Bromine in glacial acetic acid = 3-4 ml. of Bromine in 15.0 ml. of glacial acetic

Chemical Equation :

Procedure:

• Dissolve 4.0 g of acetanilide in 14.0 ml. of glacial acetic acid in a 250 ml. conical flask.
• Dissolve1.6  ml. of Bromine in 8.0 ml. of glacial acetic acid in a separating funnel. 
• Add bromine solution to acetanilide solution slowly dropwise with continuous stirring and also take care that the temperature does not exceed 40℃.
• Allow the reaction mixture to maintain the temperature. After the addition of bromine is complete an orange colour solution is obtained.
• Pour the contents of the flask in 150 ml. of ice-cold water taken in 250 ml. beaker. A white precipitate of P-Bromo acetanilide with a small amount of ortho isomer will separate out.
• Stir it thoroughly and if the solution has yellow colour add a sufficient amount of sodium bisulphide to remove it. 
• Separate the precipitate by filtration through a Buchner funnel and wash it with cold water.
• Dry the product and crystallize from ethyl alcohol or rectified spirit. 
• Note the colour, weight, and melting point of the product.

Result: x g of p-bromoacetanilide is obtained white crystalline solid.

Melting point =____℃.

Expected yeild= ____g

Let me know if you have more questions or if there is a specific topic that you would like to know more about.