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GATE 2024 CY – Question 14

Organic Chemistry · Pericyclic Reactions and Photochemistry: Electrocyclic, cycloaddition and sigmatropic reactions. Diels-Alder reaction, Claisen and Cope rearrangements and their applications in organic synthesis. FMO method of analysis. Woodward-Hoffmann rules. Photochemistry of alkenes, arenes and carbonyl compounds. Photo-oxidation and photo-reduction. Di-π-methane rearrangements, Norrish type-I and II reactions. Paternό-Büchi reaction, Photo- Curtius and Wolff rearrangements. Barton and Hofmann-Lӧffler-Freytag reactions. · 1 mark · Multiple choice

The major product in the following reaction sequence is

Photochemical rearrangement of an aryl cyclohexanone followed by boron tribromide; four product structures.
  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: (A) Option A in the figure

Explanation

The published product is A. Apply the photochemical rearrangement before BBr₃ demethylation, retaining the ring connectivity and stereochemistry shown in A. The provisional explanation identifying D as the final lactone was not supported by the official product assignment.

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