Question

What is the visible evidence of positive results for the Potassium Permanganate Test?

Answer 1

Potassium Permanganate $\left({\mathrm{KMnO}}_4\right)$ Test:

• This test is used for Aldehydes, Alkenes, and Phenols.

Reactions:

• When aldehydes are oxidized to carboxylic acid:
• $\mathrm{R}-\mathrm{CHO}\stackrel{\mathrm{oxidation}}{\to }\mathrm{RCOOH}$
• Alkenes are oxidized to glycols:
• 
• When phenols when oxidized to quinones.
• 

How to perform:

• To perform this test we take the sample in a test tube and then Pottasium permanganate solution is added to it drop by drop.

Visible indication:

• The purple color of Potassium permanganate$\left({\mathrm{KMnO}}_4\right)$ disappears and a precipitate of Manganese oxide $\left({\mathrm{MnO}}_2\right)$ is then formed.

Hence, a brown color substance is seen and the purple color disappears.