"Preparation of p bromo aniline from p bromo acetanilide"

 

"Preparation of  p bromo aniline from p bromo acetanilide"

Theory:

Para-bromoaniline is synthesized by the conversion of p-bromoacetanilide to p-bromoaniline through a hydrolysis reaction using sodium hydroxide (NaOH). The p-bromoacetanilide is reacted with NaOH, resulting in the replacement of the acetyl group with a hydroxyl group.

Chemicals Required:

1. 5 g p-Bromoacetanilide
2. Ethyl alcohol (as a solvent)
3. 5% Sodium hydroxide (NaOH) solution
4. 7 mL Concentrated hydrochloric acid (HCl)

Apparatus Required:

1. Round-bottom flask
2. Reflux condenser
3. Separatory funnel
4. Buchner funnel
5. Filter paper
6. Glass stirring rod
7. Glassware for measuring and transferring chemicals (graduated cylinders, pipettes, etc.)

Chemical Equation:

Mechanism:

Procedure:

• In a round-bottom flask, I added 5 g of p-bromoacetanilide.
• Then I fitted a reflux condenser to the flask.
• I added 7 mL of concentrated hydrochloric acid (HCl) to the flask.
• Heat the reaction mixture under reflux (boiling) for 1-2 hours. The reflux temperature should be around 70-80°C. During the reaction, the p-bromoacetanilide will react with HCl to form p-bromoacetanilide hydrochloride.
• After the reaction, Icooled the reaction mixture to room temperature.
• I transferred the reaction mixture to a separatory funnel and added water to the separatory funnel. I shaked the separatory funnel gently, allowing the layers to separate.
• I drained the lower aqueous layer (containing impurities) and discard it properly.
• I transferred the upper organic layer (containing p-bromoacetanilide) to a clean beaker.
• To the organic layer I added 5% sodium hydroxide (NaOH) solution dropwise until the pH is around 9-10. This will convert p-bromoacetanilide to p-bromoaniline.
• I stirred the mixture for some time to ensure complete conversion.
• I extracted the p-bromoaniline product by adding a suitable organic solvent (e.g., ethyl acetate or dichloromethane) to the beaker and shaked the mixture gently to ensure good extraction by using the above mentioned procedure of extarction
• I concentrated the organic solution using a rotary evaporator or by heating, once the volume was reduced, I cooled the concentrated solution in an ice bath. And collected the solid p-bromoaniline product by filtration using a Buchner funnel and filter paper.
• I rinsed the solid product with a cold solvent (e.g., cold water or ice-cold ethanol) to remove impurities.

Calculations:

Mass of p-bromoacetanilide = 5 g

Moles of p-bromoacetanilide = Mass / Molar mass

Moles of p-bromoacetanilide = 5 g / 214.1 g/mol

Moles of p-bromoacetanilide = 0.0234 mol

The stoichiometric ratio between p-bromoacetanilide and p-bromoaniline is 1:1. Therefore, the moles of p-bromoaniline formed will be the same as the moles of p-bromoacetanilide

Mass of p-bromoaniline = Moles of p-bromoaniline x Molar mass

Mass of p-bromoaniline = 0.0234 mol x 172.1 g/mol

Mass of p-bromoaniline = 4.026 g

The theoretical yield of p-bromoaniline is approximately 4.026 grams.

To calculate the percentage yield, we need the actual yield of p-bromoaniline.

Let's assume the actual yield of p-bromoaniline is 3.5 grams.

Percentage yield = (Actual yield / Theoretical yield) x 100 

Percentage yield = (3.5 g / 4.026 g) x 100 Percentage yield = 86.8%

Therefore, the theoretical yield of p-bromoaniline is approximately 4.026 grams, and the percentage yield is approximately 86.8%.