"Preparation of Acetanilide"

 

"Preparation of Acetanilide"

Theory:

Acetanilide is an organic compound that can be synthesized by acetylation of aniline. Acetylation refers to the process of introducing an acetyl group (-COCH3) to a compound. In this case, acetic anhydride will be used as the acetylating agent to react with aniline, resulting in the formation of acetanilide.

Materials Required:

• Acetic anhydride (C₄H₆O₃): Acetylating agent used to introduce the acetyl group.
• Aniline (C₆H₇N): Amine compound that undergoes acetylation to form acetanilide.
• Zinc dust (Zn): Catalyst used to promote the reaction.
• Glacial acetic acid (CH₃COOH): Solvent and reaction medium.
• Distilled water (H₂O): Used for washing and purification steps.

Chemicals Required:

1. Acetic anhydride
2. Aniline
3. Zinc dust
4. Glacial acetic acid
5. Distilled water

Chemical Equation:

Mechanism:

Procedure:

• Set up a round-bottom flask equipped with a reflux condenser and a magnetic stirrer.
• Add 10 mL of aniline to the flask.
• Slowly add 20 mL of acetic anhydride to the flask while stirring.
• Add a small amount (a few grams) of zinc dust to the reaction mixture as a catalyst.
• Heat the mixture gently under reflux for about 30 minutes. The reaction is exothermic, so monitor the temperature and adjust the heat accordingly to maintain refluxing conditions.
• After 30 minutes, remove the heat source and allow the reaction mixture to cool to room temperature.
• Carefully add the reaction mixture to a beaker containing ice-cold water while stirring vigorously. This will cause the acetanilide to precipitate out of the solution.
• Filter the precipitated acetanilide using a Buchner funnel or a simple gravity filtration setup.
• Wash the collected solid with cold distilled water to remove impurities. Repeat this washing process a few times.
• Finally, dry the acetanilide by spreading it out on a watch glass or filter paper in a well-ventilated area until it is completely dry.
• Weigh and record the yield of acetanilide obtained.
  
  
  

Calculations:

Amount of Aniline = 10ml

Molar mass of Aniline = 93 g/mol

Density of Aniline = 1.022 g/mol

Mass of Aniline = 10 x 1.02 = 9.784g

Moles of Aniline =  m/M

                    9.784÷93g/mol = 0.1052 moles

Moles of Aniline = 0.1052 moles

Amount of Acetic anhydride = 20ml

Molar mass of Acetic anhydride = 102 g/mol

Density of Acetic anhydride = 1.08 g/mol

Mass of Acetic anhydride = 20 x 1.08 = 18.51g

Moles of Acetic anhydride = m/M

                       18.51g÷102g/mol = 0.1815 moles

Moles of Acetic anhydride = 0.1815 moles

From chemical equation;

1eq of Aniline = 1eq of Acetic anhydride = 1eq of Acetanilide

so,

Molecular mass of Acetanilide = 135 g/moles

Moles of Acetanilide = 0.105 moles

Mass of Acetanilide = n×M

                                (0.105mol)(135 g/mol) = 7.77g

Theoretical yield = 7.77 g

Actual Yield = 7 g

Percentage Yield = (7 g / 7.77 g) × 100

 Percentage Yield = 90.01%

Precautions:

The reaction should be performed with caution as acetic anhydride is a corrosive and toxic compound. It is also important to wear appropriate safety equipment, such as gloves and goggles, and work in a well-ventilated area.