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GATE 2021 CY – Question 45

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

Which of the illustrated compounds can be prepared by nucleophilic substitution?

Diagram for GATE 2021 CY question 45
  1. III, IV, and V
  2. I, II, and VI
  3. II, IV, and VI
  4. I, III, and V

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Correct answer: (C) II, IV, and VI

Explanation

II can arise by substitution of an activated secondary leaving group with acetate; IV is accessible by thiolate displacement on the nitro-activated aryl ring; VI is formed by substitution at the primary phenethyl carbon with methoxide. Unactivated phenyl and vinyl carbons in I/V do not undergo ordinary SN1/SN2, and bridgehead III resists the required substitution geometry.

Thus **II, IV and VI, C**, under the standard substitution routes intended.