Experiment 6

Objective

To detect the presence of double or triple bonds in unsaturated organic compounds using the Baeyer test with alkaline potassium permanganate.

Introduction

Alkaline potassium permanganate (KMnO₄) is a strong oxidizing agent that reacts with unsaturated bonds. In the presence of double bonds, it forms dihydroxy compounds, while with triple bonds, it forms carboxylic acids. The disappearance of the pink color of KMnO₄ indicates a positive reaction, confirming the presence of unsaturation.

Reactions:

1.    Oxidation with Double Bond (e.g., Propene):

CH3​CH = CH2 ​+ [O] + H2​O → CH3​CH(OH) - CH(OH) + [O]→COOH-COOH

2.    Oxidizing Solution Preparation:

KMnO4 ​+ KOH → K2​MnO4 ​+ H2​O + [O]

Materials

Chemicals

·       Potassium permanganate (KMnO₄)

·       Potassium hydroxide (KOH)

·       Propene

Apparatus

·       Two test tubes

·       Two test tube holders

·       Dropper

·       White paper (for color contrast)

Reagents

·       Prepare 5–6 ml of alkaline KMnO₄ solution in a test tube

·       3–4 ml of propene solution in a pipette

Procedure

1.    Place the KMnO₄ solution in a test tube and secure it in a test tube holder.

2.    Add propene dropwise to the KMnO₄ solution.

3.    Continue adding until the pink color of KMnO₄ completely disappears.

4.    Observe and record any changes.

Observation

The pink color of KMnO₄ disappears, forming a clear solution, indicating the presence of unsaturation in the compound.

Questions

1.    What is an unsaturated compound?

2.    How is unsaturation detected in organic compounds?

3.    What occurs when KMnO₄ reacts with propene?

4.    What is alkaline potassium permanganate?