“Lab Report For The Synthesis of Chalcone”

 

“Lab Report For The Synthesis of Chalcone”

Theory:

Chalcone is synthesized through the Claisen-Schmidt condensation reaction between an aromatic aldehyde and an acetophenone or ketone. The reaction is catalyzed by a base, usually a strong base like sodium hydroxide, and proceeds through the formation of an enolate intermediate. The enolate reacts with the aldehyde to form the chalcone product.

Chemicals Used:

1. Sodium hydroxide (NaOH) - 5.5 grams
2. Water - 50 ml
3. Rectified spirit - 30 ml
4. Ice - 13 grams
5. Acetophenone - 5.5 ml
6. Benzaldehyde - 5 ml

Apparatus Used:

• Magnetic stirrer
• Glass beaker 
• Stir bar
• Weighing scale
• Filtration setup
• Drying apparatus

Chemical Equation:

Mechanism:

Procedure:

1. Dissolve 5.5 g of sodium hydroxide in a mixture of 50 mL of water and 15 mL of ethanol in a conical flask.

2. Cool the solution in an ice bath.

3. Add 5.4 mL of acetophenone to the cooled solution, followed by 5 mL of benzaldehyde.

4. Stir the reaction mixture continuously with a magnetic stirrer, keeping the temperature around 25 °C.

5. Continue stirring for about 2 hours until the mixture becomes viscous.

6. Pour the reaction mixture slowly into crushed ice with continuous shaking.

7. Filter the separated solid and wash it with cold water.

8. Recrystallize the crude product from a minimum amount of warm ethanol.

9. Cool the solution to obtain light yellow crystals of chalcone.

10. Filter, dry the crystals, and determine the melting point (≈ 55 °C).

Calculations

In the synthesis of chalcone, the molar ratio between acetophenone and chalcone is 1:1.

To calculate the moles, we use the formula:

Moles = Mass/Molar Mass

Molar masses of Acetophenone (C₈H₈O) = 120.15 g/mol

Molar masses of Chalcone (C₁₅H₁₂O) = 208.26 g/mol

Volume of acetophenone = 5.4 mL

Density of acetophenone = 1.028 g/mL

Mass of acetophenone = 5.4 ml

Moles of acetophenone  = 5.55/120.15g/mol = 0.0462mol

Since the molar ratio between acetophenone and chalcone is 1:1

Moles of chalcone = 0.0462 mol

Theoretical yield of chalcone

Theoretical yield = Moles of chalcone/Molar mass of chalcone

Theoretical yield = 0.0462 mol / 208.26 g/mol

Theoretical yield of Chalcone = 9.62 g

Percentage Yield:

Let’s assume the actual yield (mass of chalcone obtained experimentally) is given or measured.

For example, if the actual yield of chalcone obtained is 6.5 g, then:

Percentage yield = Actual yield / Theoretical yield X 100

Percentage yield = 6.5/9.62 X 100

Percentage Yield of Chalcone = 67.6 %