JEE Main · 2019 · Shift-IeasyHC-068

But-2-ene on reaction with alkaline KMnO4 at elevated temperature followed by acidification will give:

Hydrocarbons · Class 11 · JEE Main Previous Year Question

Question

But-2-ene on reaction with alkaline \ceKMnO4\ce{KMnO4} at elevated temperature followed by acidification will give:

Options
  1. a

    One molecule of \ceCH3CHO\ce{CH3CHO} and one molecule of \ceCH3COOH\ce{CH3COOH}

  2. b

    \ceCH3CH(OH)CH(OH)CH3\ce{CH3-CH(OH)-CH(OH)-CH3}

  3. c

    2 molecules of \ceCH3COOH\ce{CH3COOH}

  4. d

    2 molecules of \ceCH3CHO\ce{CH3CHO}

Correct Answerc

2 molecules of \ceCH3COOH\ce{CH3COOH}

Detailed Solution

Step 1: Identify Oxidation Conditions

Hot alkaline \ceKMnO4\ce{KMnO4} = oxidative cleavage of the \ceC=C\ce{C=C} double bond.

Cold dilute \ceKMnO4\ce{KMnO4} gives diol; hot conc. \ceKMnO4\ce{KMnO4} gives cleavage. image Key Points:

  • Hot alk. \ceKMnO4\ce{KMnO4}: \ceRCH=\ce{RCH=} \rightarrow \ceRCOOH\ce{RCOOH}; \ceR2C=\ce{R2C=} \rightarrow ketone; \ceH2C=\ce{H2C=} \rightarrow \ceCO2\ce{CO2}
  • Both carbons in but-2-ene are \ceCH=\ce{-CH=} type with \ceCH3\ce{CH3} group, so both give acetic acid

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