Question

Decolourisation of alkaline $KMn{O}_4$ is used as a test to distinguish :

• A. Paraffins and Olefins
• B. Benzene and paraffins
• C. Acetylenes and olefins
• D. Aldehydes and ketones

Answer 1

Answer: (A)

Paraffins and Olefins

Decolourisation of alkaline $KMn{O}_4$ (Baeyers reagent) is used as a test to distinguish Paraffins & Olefins. Alkaline $KMn{O}_4$ reacts with Olefins but not with paraffins (alkanes).
$RC{H}_2=C{H}_2+\underset{fromKMn{O}_4}{H_{2}O+O}\to RCH\left(OH\right)-CH\left(OH\right)R$
After reaction with alkenes, the bright purple colur of $KMn{O}_4$ disappears.