Question

Which of the reactions is used in the conversion of a ketone into hydrocarbon ?

• A. Reimer-Tiemann reaction
• B. Wolff-Kishner reduction
• C. Aldol condensation
• D. Stephen reaction

Hint:

Use Wolff-Kishner reduction for substrates that are sensitive to acids.
Use Clemmensen reduction \( (\text{Zn-Hg / HCl}) \) for substrates that are sensitive to bases.
Both reactions remove the oxygen and add two hydrogens to the carbonyl carbon.

Answer 1

The Correct Option is B

Step 1: Understand what the question is asking.
We need the reaction that removes the oxygen from a ketone completely and replaces the $\text{C=O}$ with $\text{CH}_2$, turning the ketone straight into a hydrocarbon.
Step 2: Check each named reaction against this requirement.
The Reimer-Tiemann reaction adds a $-\text{CHO}$ group to a phenol ring, it does not touch a ketone. The Stephen reaction converts a nitrile into an aldehyde. Aldol condensation joins two carbonyl molecules together and keeps the oxygen in the product.
Step 3: Confirm Wolff-Kishner reduction fits.
The ketone first reacts with hydrazine to form a hydrazone, and heating this hydrazone with a strong base like KOH releases nitrogen gas and leaves behind the $\text{CH}_2$ group in place of $\text{C=O}$. \[ \text{R}_2\text{C=O} \xrightarrow{\text{NH}_2\text{NH}_2} \text{R}_2\text{C=N-NH}_2 \xrightarrow{\text{KOH}, \Delta} \text{R}_2\text{CH}_2 + \text{N}_2 \]
Step 4: State the conclusion.
Since this is the only listed reaction that fully deoxygenates a ketone to a hydrocarbon, it is the correct choice.
\[ \boxed{\text{Wolff-Kishner reduction}} \]