Question

Which of the following reactions will yield benzaldehyde as a product? 
 

 

Choose the correct answer from the following options:
 

• (B) and (C)
• (C) and (D)
• (A) and (D)
• (A) and (C)

Hint:

Benzaldehyde can be synthesized by oxidation of toluene (Etard reaction), Gattermann-Koch formylation, or partial oxidation of benzyl alcohol.

Answer 1

The Correct Option is A

Step 1: Analyzing Reaction (A). 
The reaction starts with benzoic acid (C₆H₅COOH).
- SOCl₂, Quinoline: SOCl₂ converts the carboxylic acid to the corresponding acyl chloride (C₆H₅COCl). 
- H₂/Pd/BaSO₄: Hydrogenation of the acyl chloride reduces it to the corresponding aldehyde, benzaldehyde (C₆H₅CHO). Thus, Reaction (A) yields benzaldehyde.
Step 2: Analyzing Reaction (B). 
The reaction starts with benzyl alcohol (C₆H₅CH₂OH). 
- CrO₃/H₂SO₄: This reagent is used to oxidize alcohols to aldehydes. 
- Benzyl alcohol is oxidized to benzaldehyde (C₆H₅CHO). 
Step 3: Analyzing Reaction (C). 
The reaction starts with anisole (C₆H₅OCH₃).
- NaBH₄: This is a mild reducing agent that typically reduces carbonyl compounds (like esters or ketones) to alcohols. - PCC: This reagent is used to oxidize alcohols to aldehydes.
- Anisole undergoes reduction to benzyl alcohol (C₆H₅CH₂OH) via NaBH₄, and then PCC oxidizes it to benzaldehyde (C₆H₅CHO). 
Step 4: Analyzing Reaction (D). 
The reaction starts with toluene (C₆H₅CH₃). - CrO₃: Chromium trioxide oxidizes methyl groups (CH₃) to the corresponding aldehyde, resulting in benzaldehyde. - (CH₃CO)₂O is a reagent typically used in Friedel-Crafts acylation, but in this reaction setup, it does not interfere with the oxidation step. The final product is benzaldehyde. Thus, Reaction (D) gives benzaldehyde. 
Conclusion: The reactions that yield benzaldehyde are (A) and (D). Therefore, the correct answer is (C) (A) and (D).