JEE Advanced 2019 · Paper 2 · Chemistry Q13

← JEE Advanced 2019 · Paper 2

ChemistryNumerical+3Question 31 of 54

Total number of hydroxyl groups present in a molecule of the major product P is ______

1-(Cyclopent-2-enyl)-4-(cyclohex-3-enyl)but-2-yne (cyclopentene-CH₂-C≡C-CH₂-cyclohexene) treated with (i) H₂, Pd-BaSO₄, quinoline, (ii) dil. KMnO₄ (excess), 273 K, gives P.

Your answer

Answer and worked solution

Official answer: 6

Step (i). Lindlar's catalyst reduces the alkyne to a cis alkene. The molecule now has three C=C bonds: in the cyclopentene ring, in the chain, and in the cyclohexene ring.

Step (ii). Cold dilute $\ce{KMnO4}$ in excess syn-dihydroxylates every C=C, adding two OH groups to each.

So P has $3\times2=6$ OH groups.

Answer: 6

Topics:Alkenes Alkynes Alcohols

← Previous question Next question →

JEE Advanced 2019 · Paper 2, Chemistry question 13