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

The reactions that yield benzaldehyde as a product are:

(A) and (D)

Detailed Explanation:

1. Reaction (A):
   • In the first step, benzoic acid reacts with SOCl₂ and quinoline to form benzoyl chloride (C₆H₅-COCl).
   • In the second step, Rosenmund reduction using H₂/Pd-BaSO₄ converts benzoyl chloride to benzaldehyde.
   • This reaction yields benzaldehyde.
2. Reaction (B):
   • Benzyl alcohol (C₆H₅-CH₂OH) is oxidized by CrO₃/H₂SO₄ to form benzoic acid (C₆H₅-COOH), not benzaldehyde.
   • This reaction does not yield benzaldehyde.
3. Reaction (C):
   • In the first step, acetophenone (C₆H₅-CO-CH₃) is reduced using NaBH₄ to benzyl alcohol (C₆H₅-CH₂OH).
   • In the second step, oxidation using PCC converts benzyl alcohol to benzaldehyde.
   • This reaction yields benzaldehyde.
4. Reaction (D):
   • Toluene (C₆H₅-CH₃) undergoes oxidation with CrO₃/(CH₃CO)₂O followed by hydrolysis to selectively form benzaldehyde instead of complete oxidation to benzoic acid.
   • This reaction yields benzaldehyde.

Concept

• Benzaldehyde can be formed via selective reduction (e.g., Rosenmund reduction) or controlled oxidation (e.g., using CrO₃ with acetic anhydride).
• Reactions involving complete oxidation (e.g., with CrO₃ alone) lead to benzoic acid, not benzaldehyde.
• Reduction of benzoyl chloride and partial oxidation of toluene are key methods to synthesize benzaldehyde.