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ChemistryInteger+4Question 37 of 57

JEE Advanced 2021 · Paper 1, Chemistry question 18

In the reaction given below, the total number of atoms having sp2sp^2 hybridization in the major product P\mathbf P is ____.

A tricyclic diene: a cyclooctadiene ring whose two C=C bonds (on opposite sides of the ring) are each fused to a cyclopentane ring. Reagents: 1. O3 (excess), then Zn/H2O; 2. NH2OH (excess); product P.
Answer and worked solution

Official answer: 8

Ozonolysis. Both C=C bonds are tetrasubstituted and each sits at a ring fusion. Cutting them gives a single large ring with four ketone C=O groups: a cyclotetradecane-tetraone, CX14HX20OX4\ce{C14H20O4}.

Oxime formation. Excess NHX2OH\ce{NH2OH} turns all four ketones into oximes, C=N−OH\ce{C=N-OH}.

Counting sp² atoms. Each oxime has an sp² carbon and an sp² nitrogen: 4×2=4\times2= 8. The key also accepts 12, which counts the four oxime oxygens as sp² as well.

Topics:Nucleophilic additionAlkenesHybridisation
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