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GATE 2022 CY – Question 41

Organic Chemistry · Types of Reactions: Nucleophilic and electrophilic substitution reactions (both aromatic and aliphatic). Addition reactions to carbon-carbon and carbon-heteroatom (N and O) multiple bonds. Elimination reactions. Reactive intermediates – carbocation, carbanion, carbenes, nitrenes, arynes and free radicals. Molecular rearrangements. Barton decarboxylation and Barton-McCombie reaction, Hunsdiecker reaction. · 2 marks · Multiple choice

The major products M and N in the given reaction sequence are

Diagram for GATE 2022 CY question 41
  1. Diagram A
  2. Diagram B
  3. Diagram C
  4. Diagram D

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Show answer and explanation

Correct answer: (B) Diagram B

Explanation

Methoxycarbonylation activates the ketone α-position. Bromination followed by methoxide induces Favorskii-type ring contraction and elimination to the cyclopentene bearing adjacent ester groups, M. Excess DIBAL reduces both methyl esters to CH2OH while preserving the alkene. The pair with both the contracted ring and retained C=C is **B**.