Question

In the given reaction :

• A. (A)
• B. (B)
• C. (C)
• D. (D) B and C both

Answer 1

Answer: (D)

D

Answer 2

The reaction given is the treatment of cyclohexene with cold, dilute potassium permanganate ($KMnO_4$), also known as Baeyer's reagent.

1. Nature of Reagent: Cold, dilute, alkaline $KMnO_4$ is a mild oxidizing agent used for the hydroxylation of alkenes. It is specifically known to cause syn-dihydroxylation.
2. Syn-dihydroxylation: This means that two hydroxyl (-OH) groups are added to the carbons of the double bond from the same face (or side) of the alkene.
3. Product of Cyclohexene: When cyclohexene undergoes syn-dihydroxylation, the double bond breaks, and two -OH groups are added to the adjacent carbon atoms. Since the addition is syn, both -OH groups will be on the same side of the cyclohexane ring. This product is cis-cyclohexane-1,2-diol.

Since the starting material (cyclohexene) is achiral and the reagent (cold $KMnO_4$) is also achiral, the reaction will yield a racemic mixture of two enantiomers in equal amounts. Therefore, both B and C are formed as products.

• Option A shows a trans-1,2-diol (one -OH is wedge, one is dash), which would result from anti-dihydroxylation, not syn-dihydroxylation by Baeyer's reagent.
• Option B shows one enantiomer of the cis-1,2-diol.
• Option C shows the other enantiomer of the cis-1,2-diol.
• Option D correctly states that both B and C are formed.

The final answer is D