The reduction of cyclohexanone with \( LiAlH_4 \) will give:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Cyclohexanol
Lithium aluminium hydride, \( \ce{LiAlH4} \), is a source of hydride ions (\( \ce{H-} \)). The hydride adds to the carbonyl carbon and, after work-up with water, the oxygen picks up a proton. Cyclohexanone is a ketone, so it gives the secondary alcohol cyclohexanol:
\( \displaystyle \ce{C6H10O} \xrightarrow[\text{(ii) }\ce{H2O}]{\text{(i) }\ce{LiAlH4}} \ce{C6H11OH} \)
The >C=O group of the ring becomes >CH–OH; the ring itself is unchanged.
Why the other options are incorrect
Option (2) Cyclohexanaldehyde — Incorrect. Reduction adds hydrogen; it cannot turn a ketone into an aldehyde, which would need a change in the carbon skeleton.
Option (3) Benzoic acid — Incorrect. An acid is a product of oxidation, and benzoic acid has an aromatic ring and seven carbon atoms; cyclohexanone has a saturated six-carbon ring.
Option (4) Phenol — Incorrect. Phenol is aromatic; forming it from cyclohexanone would need dehydrogenation (removal of hydrogen), the opposite of what \( \ce{LiAlH4} \) does.
NCERT (2026-27 edition):
Reduction
