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GATE 2025 CY – Question 55

Organic Chemistry · Oxidation: Oxidation of alcohols involving metal and non-metal-based (chromium, manganese, DMSO, and hypervalent iodine) reagents. Peracid oxidation of alkenes and carbonyls. Alkenes to diols (manganese and osmium-based reagents), alkenes to carbonyls with bond cleavage (ozonolysis), and alkenes to alcohols/carbonyls without bond cleavage (hydroboration-oxidation). Asymmetric epoxidations (Sharpless and Jacobsen) and Sharpless asymmetric hydroxylation. · 2 marks · Multiple select

For the following reaction, the possible product(s) is/are

Enantiopure ethylcyclohexenone treated with methylmagnesium bromide, PCC and catalytic hydrogenation; four chair 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; (C) Option C in the figure

Explanation

Methyl addition gives a tertiary allylic alcohol. PCC causes oxidative allylic transposition; hydrogenation creates either configuration at the new methyl-bearing center while retaining the original ethyl-bearing stereocenter. The retained ethyl configuration selects A and C.

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