In Clemmensen reduction the reagents are:
A. \(Zn-Hg\)
B. \(HCl\)
C. \(Zn\)
D. \(H_2SO_4\)
E. \(Cu\)
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → A and B only
In the Clemmensen reduction the carbonyl group of an aldehyde or a ketone is reduced to a \( \ce{CH2} \) group by zinc amalgam (Zn–Hg) and concentrated hydrochloric acid; for example, acetone gives propane:
\( \displaystyle \ce{CH3COCH3 + 4[H]} \xrightarrow[\text{conc. }\ce{HCl}]{\ce{Zn-Hg}} \ce{CH3CH2CH3 + H2O} \)
The same reduction can be done in basic medium by the Wolff-Kishner reduction (hydrazine, then KOH in ethylene glycol on heating).
(A) \(Zn-Hg\) — Correct. Zinc amalgam is the reducing agent.
(B) \(HCl\) — Correct. Concentrated HCl is the acid used.
(C) \(Zn\) — Incorrect. Plain zinc is not used; it must be amalgamated with mercury.
(D) \(H_2SO_4\) — Incorrect. The acid of the Clemmensen reduction is hydrochloric acid.
(E) \(Cu\) — Incorrect. Copper plays no part in this reduction.
NCERT (2026-27 edition):
Reduction to Hydrocarbons
