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ChemistryInteger+4 / -1Question 60 of 90

JEE Main 2022 · 30 Jul · Shift 2, Chemistry question 60

Among the following, how many hydrocarbon (s) with formula C10_{10}H16_{16} which on reaction with acidic potassium permagenate yield(s) same product ? _______

Five hydrocarbons: (1) 1-isopropenyl-4-methylcyclohexane; (2) a cyclobutene with the C=C away from the substituents, a methyl on one sp3 ring carbon and a 3-methylbut-3-enyl chain on the next; (3) 1,2-dimethylcyclopentene with an allyl group on the ring carbon next to the C=C; (4) 1-methylcyclobutene carrying a 3-methylbut-3-enyl chain on C4; (5) a cyclopropene carrying a 3-methylbut-3-enyl chain.
Answer and worked solution

Official answer: 2

Oxidative cleavage. Hot acidic KMnO₄ cuts every C=C: =CH₂ ends become CO₂, =CH- becomes COOH, and =CR₂ becomes a ketone.

Matching pair. The cyclopentene (3): cleaving the C(CH₃)=C(CH₃) ring bond and the allyl group gives CH3CO−CH(CH2COOH)−CH2CH2−COCH3\mathrm{CH_3CO{-}CH(CH_2COOH){-}CH_2CH_2{-}COCH_3}. The 1-methylcyclobutene (4): the ring opens to CH3CO−CH(…)−CH2COOH\mathrm{CH_3CO{-}CH(\ldots){-}CH_2COOH} and the side chain becomes CH2CH2COCH3\mathrm{CH_2CH_2COCH_3}: the same keto acid. The other three give different products. So 2.

Answer: 2

Topics:Alkenes
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