Question

19. The final major product obtained in the following reaction is __

1. conc. H2SO4, Δ

2. KMnO4, H , Δ

• A. Chemical structure of a benzene ring fused to a five-membered ring. The benzene ring has a carboxylic acid group (HOOC) attached to one carbon. The five-membered ring is a cyclic anhydride with two carbonyl groups (C=O) and an oxygen atom (O) in the ring.
• B. Chemical structure of a benzene ring fused to a five-membered ring. The benzene ring has a carboxylic acid group (COOH) attached to one carbon. The five-membered ring is a cyclic anhydride with two carbonyl groups (C=O) and an oxygen atom (O) in the ring.
• C. Chemical structure of a benzene ring with two carboxylic acid groups (COOH) attached to adjacent carbons.
• D. Chemical structure of a benzene ring with three carboxylic acid groups (COOH) attached to carbons in a 1,3,5 arrangement.

Answer 1

Answer: (A)

A)

Chemical structure of a benzene ring fused to a five-membered ring. The benzene ring has a carboxylic acid group (HOOC) attached to one carbon. The five-membered ring is a cyclic anhydride with two carbonyl groups (C=O) and an oxygen atom (O) in the ring.

Answer 2

Explanation of the solution:

1. Step 1 (Conc. H₂SO₄, Δ): The acid‐catalyzed conditions dehydrate and rearrange the bicyclic precursor so that it aromatizes.
2. Step 2 (KMnO₄, H⁺, Δ): The formed aromatic ring has a benzylic –CH₃ group; strong oxidation converts this group to –COOH. Under the reaction conditions, the o‐dicarboxylic acid thus produced cyclizes to form a five‐membered cyclic anhydride ring fused to the benzene ring (i.e. phthalic anhydride).