PREPARATION OF BENZILIC ACID

OBSERVATION AND CALCULATIONS:-

Molecular weight of benzil = 210.0g

Molecular weight of benzilic acid = 228.0g

210.0g of benzil yields benzilic acid = 228.0g

1.0g of benzil yields benzilic acid = 228/210g

3.0g of benzil yields benzilic acid = 228/210 ´ 3

= 3.25g

Theoretical yield = 3.25g

Practical yield = 2.5g

Percentage yield = Practical yield/Theoretical yield ´ 100

= 2.5/3.25 * 100

= 76%

RESULT:- Percentage yield of benzilic acid is 76%.

APPARATUS:- Round bottom flask, Burner, Stand, Beaker, Funnel, Condenser, Water bath, stirrer etc.

CHEMICALS:-

Benzil

Potassium hydroxide

Ethyl Alcohol

Hydrochloric Acid

PROCEDURE:-

1. Took 3.0g of benzil in round bottom flask.

2. Took 3.0g of potassium hydroxide dissolved in 10.0ml of water, added to it 10.0ml of ethanol (90%).

3. Added alcoholic potassium hydroxide solution (as in no.2) in benzil (as in no.1).

4. Refluxed the reaction mixture for 20 minutes over water bath.

5. Transferred the reaction mixture (in a small beaker) immediately into the ice bath. Stirred continuously until solution was cooled. The potassium salt of benzilic acid was precipitated out.

6. Filtered the precipitates.

7. Precipitates were dissolved in 30.0ml of water and acidified with 3 drops of concentrated hydrochloric acid with stirring.

8. Re-filtered and dried the precipitates.

9. PURIFICATION:- Dry precipitates were washed with 10.0ml of cold water and filtered, dried and again washed with 5.0ml of benzene, re-filtered and dried.

10. Precipitates were weighed and percentage yield was calculated.