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JEE Advanced levelOne or more correct optionsDifficulty 3 of 3nm053

Each statement describes a ring compound and proposes a name. Which statement(s) is/are correct?

  1. AA cyclohexene with a methyl group on the sp3 carbon farthest from the double bond is named 4-methylcyclohexene.
  2. BA cyclopentane ring with an ethyl group and a methyl group on adjacent carbons is named 2-ethyl-1-methylcyclopentane.
  3. CA cyclohexene with a methyl group on the sp3 carbon adjacent to the double bond is named 3-methylcyclohexene.
  4. DA cyclohexene with a methyl group on the sp3 carbon adjacent to the double bond is named 6-methylcyclohexene.

Answer: A, C

In 1-ethyl-2-methylcyclopentane the two substituents are on adjacent carbons; the tie in locants {1,2} is broken in favour of the alphabetically first prefix (ethyl) getting 1, so '2-ethyl-1-methyl' is wrong. In cyclohexene the double bond is C1=C2; the sp3 carbon next to C2 is C3 (never 6), so 3-methylcyclohexene is correct. The farthest sp3 carbon is C4 (equivalent to C5), so 4-methylcyclohexene is correct. The adjacent-carbon methyl compound is therefore 3-methylcyclohexene, so 6-methylcyclohexene is wrong.
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