GATE 2025 CY – Question 27

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 select

Choose the correct option(s) with regard to mechanism of the following transformation.

Photochemical norbornadiene-to-cycloheptatriene rearrangement.

It proceeds through divinyl cyclopropane rearrangement
It involves a diradical intermediate
It proceeds through di-$\pi$-methane rearrangement
It proceeds through [2+2+2] cycloaddition reaction

Practise this question in The GATE Grind →

Show answer and explanation

Correct answer: (B) It involves a diradical intermediate; (C) It proceeds through di-$\pi$-methane rearrangement

Explanation

Select B and C. The photochemical transformation is classified as a di-pi-methane rearrangement involving a diradical intermediate. It is not the divinylcyclopropane rearrangement claimed in A, nor a [2+2+2] cycloaddition.

Official GATE 2025 answer key: https://gate2026.iitg.ac.in/doc/download/2025_Key/CY_Keys.pdf