Question

Which of the following is obtained by Wolff Kishner reduction?

• A. $>$CH$_2$ group
• B. –NO$_3$ group
• C. –OH group
• D. $>$C=O group

Hint:

Remember: Wolff–Kishner reduction and Clemmensen reduction both convert carbonyl groups to methylene groups. Wolff–Kishner is done under strongly basic conditions, while Clemmensen uses acidic conditions with Zn–Hg/HCl.

Answer 1

The Correct Option is A

Step 1: Recall the Wolff–Kishner reduction.
The Wolff–Kishner reduction is a method used to reduce carbonyl compounds (aldehydes and ketones) to alkanes.
The reaction involves treating the carbonyl compound with hydrazine (NH$_2$NH$_2$) in the presence of a strong base (KOH) and heating, which removes the oxygen atom completely as N$_2$ gas.

Step 2: General reaction.
\[ R_2C=O \; \xrightarrow[\Delta]{NH_2NH_2/KOH} \; R_2CH_2 \] Thus, a carbonyl group ($>$C=O) is converted into a methylene group ($>$CH$_2$).

Step 3: Analyze the given options.
- (A) $>$CH$_2$ group: This is exactly what is obtained after Wolff–Kishner reduction. Correct.
- (B) –NO$_3$ group: Not involved in this reaction.
- (C) –OH group: Obtained by partial reduction, not Wolff–Kishner.
- (D) $>$C=O group: This is the starting group, not the product.
Step 4: Final Answer.
Hence, the product obtained is the methylene group ($>$CH$_2$).
\[ \boxed{>CH_2 \; \text{group}} \]