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JEE Advanced levelOne or more correct optionsDifficulty 3 of 3nm022

Which of the following statements is/are correct?

  1. ACyclohexene and 3-methylcyclopentene have the same degree of unsaturation.
  2. BPropanenitrile, , has a degree of unsaturation of 3.
  3. CEvery compound that contains a benzene ring has a degree of unsaturation of at least 4.
  4. DPent-1-en-4-yne and cyclopentene have the same degree of unsaturation.

Answer: A, C

Cyclohexene and 3-methylcyclopentene are both C6H10, each with DU 2, so the first statement is correct. A benzene ring alone accounts for 1 ring + 3 C=C = 4, so DU is at least 4. Pent-1-en-4-yne (C5H6) has DU 3, while cyclopentene (C5H8) has DU 2, so they differ. Propanenitrile (C3H5N) has DU = (6 + 2 + 1 - 5)/2 = 2, because the C-N triple bond counts as two pi bonds, not three.
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