Asked in Premeth Test 18 — Alkyl Halides, Aldehydes and Ketones, Atomic Structure (20 March 2025) 2025Moderate

In the presence of hot alkaline potassium permanganate solution 2-butene will give

Correct answer: C. Two moles of ethanoic acid

  • A. Formic acid + acetic acid
  • B. Two moles of methanoic acid
  • C. Two moles of ethanoic acid
  • D. Ethylene glycol

Explanation

2-butene is a symmetrical alkene, and when it undergoes oxidative cleavage with hot alkaline KMnO4, each carbon-carbon double bond is cleaved, and each carbon atom is oxidized to a carboxylic acid. Thus, two moles of ethanoic acid (acetic acid) are formed.Option A (Formic acid + acetic acid) is incorrect because 2-butene does not produce formic acid; it is not a terminal alkene.Option B (Two moles of methanoic acid) is incorrect because symmetrical alkenes like 2-butene do not produce methanoic acid.Option C (Two moles of ethanoic acid) is correct for the reasons explained above.Option D (Ethylene glycol) is incorrect because ethylene glycol is a product of hydroxylation, not oxidative cleavage.

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About Alkenes

Alkenes are unsaturated hydrocarbons containing a carbon-carbon double bond with sigma and pi components and restricted rotation. Their reactions include electrophilic addition of hydrogen, halogens, hydrogen halides and water, with Markovnikov orientation, oxidation, combustion and polymerisation, while their preparation commonly involves elimination from alkyl halides or alcohols.

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