Question

The structures A and B formed in the following reaction are : [Ph = \(-\mathrm{C_6H_5}\)]

• A.

  

• B.

  

• C.

  

• D.

  

Hint:

Benzene undergoes Friedel-Crafts acylation with succinic anhydride (ring opening) to give a keto acid A; Zn/Hg with HCl (Clemmensen reduction) then reduces only the ketone C=O to CH2.

Answer 1

The Correct Option is D

Benzene + succinic anhydride with \(\mathrm{AlCl_3}\) (2 eq): Friedel-Crafts acylation with ring opening of the anhydride gives \(\mathrm{Ph-CO-CH_2-CH_2-COOH}\), 4-oxo-4-phenylbutanoic acid (A). Two equivalents of \(\mathrm{AlCl_3}\) are needed because one is complexed by the carboxylate.
Clemmensen reduction (Zn/Hg, HCl) converts the aryl ketone \(\mathrm{C=O}\) to \(\mathrm{CH_2}\) while the \(\mathrm{COOH}\) group is untouched: \(\mathrm{Ph-CH_2-CH_2-CH_2-COOH}\), 4-phenylbutanoic acid (B).
This is option (4).
Answer: (4) A = 4-oxo-4-phenylbutanoic acid, B = 4-phenylbutanoic acid