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GATE 2022 CY – Question 26

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. · 1 mark · Multiple select

The CORRECT reagent(s) for the given reaction is(are)

Diagram for GATE 2022 CY question 26
  1. $H_2O_2$, NaOH
  2. Dimethyldioxirane (structure B in the figure)
  3. DIBAL-H, then mCPBA
  4. $SO_3\cdot$pyridine, $Me_2SO$

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Correct answer: (A) $H_2O_2$, NaOH; (B) Dimethyldioxirane (structure B in the figure)

Explanation

Alkaline hydrogen peroxide epoxidizes the electron-deficient enone by conjugate addition and ring closure, A. Dimethyldioxirane transfers oxygen directly across the C=C bond, B. DIBAL first reduces the carbonyl and would not retain the target ketone; SO3·pyridine/DMSO is an alcohol oxidation system. **Select A, B**.