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GATE 2024 CY – Question 25

Organic Chemistry · Heterocyclic Compounds: Nomenclature of mono- and bicyclic, as well as mono- and di-heteroatomic compounds, Structure, preparation, properties and reactions of furan, pyrrole, thiophene, pyridine, indole, quinoline and isoquinoline. · 1 mark · Multiple select

The reaction(s) that yield(s) 2-methylquinoline as the major product is (are)

Four quinoline syntheses with their substrates and reagents.
  1. Option A in the figure
  2. Option B in the figure
  3. Option C in the figure
  4. Option D in the figure

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Show answer and explanation

Correct answer: (B) Option B in the figure; (D) Option D in the figure

Explanation

Crotonaldehyde and aniline undergo Doebner–Miller cyclization and oxidation to quinaldine. Isatin and acetone undergo Pfitzinger condensation, followed by decarboxylation on acidic heating. Acetaldehyde in A gives unsubstituted quinoline; ring expansion in C places the methyl at a different position.

Official GATE 2024 answer key: https://gate2026.iitg.ac.in/doc/download/2024/CYFinalAnswerKey.pdf