Question

For which of the following compounds doesn't decolorise Baeyer’s reagent?

• A. Cyclopentene
• B. Cyclopentane
• C. pent-1-ene
• D. pent-2-ene

Answer 1

The correct option is B Cyclopentane

Baeyer’s reagent : alkaline cold & dil. $KMn{O}_4$. It is used as a test for unsaturation. $KMn{O}_4$ decolorizes (from pink to colorless).

$\text{Alkene + Baeyer’s reagent}\to \text{Vicinal Glycol derivative}$

Alkanes do not give this test, and hence decolorization is not observed.
So (b) cyclopentane does not decolorizes $KMn{O}_4$