A Levels Chemistry (9701)•9701/12/M/J/25

Explanation
Propane yields propene, which cleaves to formic and acetic acids
Steps:
- Alkane C4H8 likely erroneous for C3H8 (propane); it has two nonequivalent hydrogens, yielding 1-chloropropane and 2-chloropropane via free radical chlorination.
- Ethanolic KOH dehydrohalogenates both to the same alkene T: propene (CH3CH=CH2).
- Hot concentrated dilute KMnO4 oxidatively cleaves propene's double bond.
- The =CH2 group forms HCOOH; the =CHCH3 group forms CH3COOH.
Why B is correct:
- Oxidative cleavage of terminal alkene CH3CH=CH2 yields CH3COOH from the substituted carbon and HCOOH from =CH2 under dilute conditions preventing further oxidation to CO2.
Why the others are wrong:
- A: =CH2 oxidizes to HCOOH (dilute KMnO4), not CO2 (vigorous conditions).
- C: Ignores HCOOH from =CH2; only CH3COOH would imply symmetrical internal alkene like but-2-ene.
- D: Same as C; duplicate option, incomplete products.
Final answer: B
Topic: Hydrocarbons
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