JEE Main · 2021 · Shift-ImediumHC-116

Considering the above chemical reaction, identify the product X:

Hydrocarbons · Class 11 · JEE Main Previous Year Question

Question

image Considering the above chemical reaction, identify the product X:

Options
  1. a

    image

  2. b

    image

  3. c

    image

  4. d

    image

Correct Answerb

image

Detailed Solution

Step 1: Identify the Starting Material

4-methyl anisole = para-methyl anisole = 1-methoxy-4-methylbenzene (\ceCH3C6H4OCH3\ce{CH3-C6H4-OCH3}, methyl and methoxy groups para to each other).

Step 2: Alkaline KMnO4 Oxidation

Hot alkaline \ceKMnO4\ce{KMnO4} oxidizes alkyl side chains on aromatic rings to \ceCOOH\ce{-COOH}: image The \ceCH3\ce{-CH3} group is oxidized to \ceCOOH\ce{-COOH}. The \ceOCH3\ce{-OCH3} group is not oxidized under these conditions.

Product X = 4-methoxybenzoic acid (anisic acid): \ceHOOCC6H4OCH3\ce{HOOC-C6H4-OCH3} (para).

Key Points:

  • Alkaline \ceKMnO4\ce{KMnO4}: oxidizes \ceCH3\ce{-CH3} (or any alkyl) on benzene ring to \ceCOOH\ce{-COOH}
  • \ceOCH3\ce{-OCH3} (methoxy ether) is NOT oxidized under these conditions
  • Both \ceCH3\ce{-CH3} and \ceC2H5\ce{-C2H5} etc. on ring all give \ceCOOH\ce{-COOH}

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