Question

Which from following reactions converts carbonyl group of aldehydes and ketones to methylene group on treatment with zinc amalgam and concentrated HCl ?

• A. Wolf-Kishner reaction
• B. Stephen reduction
• C. Clemmensen reduction
• D. Rosenmund reduction

Hint:

To avoid confusing the two alkane-forming reductions:
Clemmensen uses Chloric acid (HCl) — Acidic medium.
Wolff-Kishner uses a Base (KOH) — Basic medium.

Answer 1

The Correct Option is C

Step 1: Read the reagents.
We need the named reaction that uses zinc amalgam with concentrated HCl and turns C=O into $\text{CH}_2$.

Step 2: Match the conditions.
Wolff-Kishner does the same job but in a basic mix with hydrazine. Stephen and Rosenmund only partly reduce nitriles or acid chlorides to aldehydes.

Step 3: Name it.
The acidic Zn-Hg with HCl route is the Clemmensen reduction.
\[ \boxed{\text{Clemmensen reduction}} \]