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JEE Main · 2021 · 17 Mar 2021 · Shift 2 · Hydrocarbons

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Given below are two statements:
Statement I : 2-methylbutane on oxidation with gives 2-methylbutan-2-ol.
Statement II: n-alkanes can be easily oxidised to corresponding alcohols with . Choose the correct option:
  1. (A)Both statement I and statement II are correct
  2. (B)Both statement I and statement II are incorrect
  3. (C)Statement I is correct but statement II is incorrect✓ Correct
  4. (D)Statement I is incorrect but statement II is correct

Answer: (C)

Solution

Potassium permanganate attacks a carbon-hydrogen bond of an alkane only where that bond is weak enough to be abstracted, and in a branched alkane this is the tertiary carbon-hydrogen bond. 2-Methylbutane has one such hydrogen, on C-2, and oxidation puts a hydroxyl group there to give 2-methylbutan-2-ol, so the first statement holds. Straight-chain alkanes have only primary and secondary hydrogens, which permanganate leaves untouched under these conditions, so they are not converted to the corresponding alcohols. Statement I is correct but Statement II is incorrect.

JEE Main · 2021 · 17 Mar 2021 · Shift 2 · Single correct option

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