Question

The product \(Q\) of the following reaction is

• A. 1
• B. 2
• C. 3
• D. 4

Hint:

Friedel-Crafts acylation first introduces an acyl group on benzene. Clemmensen reduction then converts the carbonyl group into a methylene group: \[ C_6H_5COCH_2CH_3 \rightarrow C_6H_5CH_2CH_2CH_3 \]

Answer 1

The Correct Option is B

Step 1: Identify the Friedel-Crafts acylation reaction.
Benzene reacts with an acid chloride (RCOCl) in the presence of AlCl₃ (Lewis acid catalyst) to give an aryl ketone via electrophilic aromatic substitution. This is Friedel-Crafts acylation.
Step 2: Determine the product of acylation.
If the acid chloride is CH₃CH₂COCl (propanoyl chloride), benzene undergoes acylation to give phenyl ethyl ketone (propiophenone): C₆H₅COCH₂CH₃.
Step 3: Identify any subsequent reduction step.
A Clemmensen reduction (Zn-Hg/HCl) or Wolff-Kishner reduction converts the carbonyl (C=O) to CH₂. Propiophenone $\rightarrow$ propylbenzene (C₆H₅CH₂CH₂CH₃).
Step 4: Explain why acylation followed by reduction is preferred over direct alkylation.
Friedel-Crafts alkylation can lead to polyalkylation and carbocation rearrangements. Acylation gives a pure product (resonance-stabilized acylium ion, no rearrangement), and subsequent reduction gives the clean alkyl product.
Step 5: Identify the final product matching option 2.
Based on the image-described reaction sequence (Friedel-Crafts acylation then reduction), the product is a propyl-substituted benzene or the intermediate aryl ketone, matching option 2.
Step 6: Conclusion.
Friedel-Crafts acylation of benzene with propanoyl chloride/AlCl₃ gives propiophenone; Clemmensen reduction gives propylbenzene. The correct product matches option 2.
\[ \boxed{\text{Product = option 2 (Friedel-Crafts acylation product)}} \]