IIT-JEE 2011 · Paper 1 · Chemistry Q15

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ChemistrySingle correct+3 / -1Question 15 of 69

Passage

Paragraph for Question Nos. 15 and 16

An acyclic hydrocarbon P, having molecular formula $\ce{C6H10}$ , gave acetone as the only organic product through the following sequence of reactions, in which Q is an intermediate organic compound.

P (C₆H₁₀) → [(i) dil. H₂SO₄/HgSO₄; (ii) NaBH₄/ethanol; (iii) dil. acid] → Q → [(i) conc. H₂SO₄ (catalytic amount) (−H₂O); (ii) O₃; (iii) Zn/H₂O] → 2 acetone.

The structure of compound P is

\ce{CH3CH2CH2CH2-C#C-H}

\ce{H3CH2C-C#C-CH2CH3}

\ce{(CH3)2CH-C#C-CH3}

\ce{(CH3)3C-C#C-H}

Answer and worked solution

Official answer: D

Work back from acetone. 2 acetone come from ozonolysis of $\ce{(CH3)2C=C(CH3)2}$ .

That alkene forms from $\ce{(CH3)3C-CH(OH)CH3}$ by dehydration with a methyl shift (secondary → tertiary carbocation).

This alcohol comes from NaBH₄ reduction of $\ce{(CH3)3C-CO-CH3}$ , the Markovnikov hydration product of $\ce{(CH3)3C-C#CH}$ (C₆H₁₀).

(D)

Topics:Alkynes Alkenes

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IIT-JEE 2011 · Paper 1, Chemistry question 15