Which of the following products is obtained when cyclohexanone is treated with sodium borohydride (NaBH4) in ethanol?
Answer
Cyclohexanol
The correct answer is Cyclohexanol — Thus cyclohexanone (a ketone) is reduced to cyclohexanol (a secondary alcohol).
Step-by-step solution
- Identify the reagent: NaBH4 is a mild reducing agent that donates hydride ions (H⁻) to carbonyl groups.
- Cyclohexanone contains a C=O carbonyl group; NaBH4 will add a hydride to the carbonyl carbon and a proton to the oxygen.
- The addition converts the carbonyl (C=O) into a hydroxyl (C–OH) group, giving the corresponding alcohol.
- Thus cyclohexanone (a ketone) is reduced to cyclohexanol (a secondary alcohol).
Common mistake: Confusing NaBH4 with a strong reducing agent that can also reduce C–X bonds; it only reduces C=O.
Concept tested: Reduction of carbonyl compounds
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