Aldehydes and Ketones I: Introduction to Carbonyl Chemistry

Experiment: Carbonyl Condensation Reactions

Objective:
To demonstrate the reactivity of aldehydes and ketones in condensation reactions.
Materials:

• Benzaldehyde
• Acetone
• Sodium hydroxide solution (10%)
• Tollens' reagent
• Fehling's reagent
• Test tubes

Procedure:
Step 1: Benzaldehyde-Acetone Condensation

1. In a test tube, add 5 mL of benzaldehyde and 5 mL of acetone.
2. Add a few drops of sodium hydroxide solution.
3. Shake the test tube gently and observe the formation of a white precipitate.

Step 2: Tollen's Test

1. In a separate test tube, add 5 mL of the reaction mixture from Step 1.
2. Add 1 mL of Tollens' reagent.
3. Heat the test tube in a water bath for a few minutes.
4. Observe the formation of a silver mirror on the walls of the test tube.

Step 3: Fehling's Test

1. In another test tube, add 5 mL of the reaction mixture from Step 1.
2. Add 1 mL of Fehling's reagent A and 1 mL of Fehling's reagent B.
3. Heat the test tube in a water bath for a few minutes.
4. Observe the formation of a brick-red precipitate.

Significance:
This experiment demonstrates the following key procedures and concepts:

• Condensation reaction: Aldehydes and ketones react with each other in the presence of a base to form a new carbon-carbon bond.
• Carbonyl reactivity: Aldehydes and ketones are reactive toward nucleophiles and reducing agents.
• Tollens' test: Aldehydes react with Tollens' reagent to form a silver mirror, indicating the presence of an aldehyde group.
• Fehling's test: Aldehydes and ketones react with Fehling's reagent to form a brick-red precipitate, indicating the presence of a reducing sugar.

This experiment provides a practical understanding of the chemistry of aldehydes and ketones and their reactivity in condensation reactions.