Hydroboration of 2 - butyne with (C₆ H₁₁)₂ BH yields the intermediate U, which on treatment with I₂ and NaOMe… · ABC26OR0695
Subject: Organic Chemistry · Chapter: Reagents, Reaction Mechanisms & Named Reactions · Topic: Reagents, Reaction Mechanisms & Named Reactions – General · Exam: GATE 2000-2022 · Marks: 2 · Difficulty: Medium
Hydroboration of 2 - butyne with $\left(\mathrm{C}_{6} \mathrm{H}_{11}\right)_{2} \mathrm{BH}$ yields the intermediate U , which on treatment with $\mathrm{I}_{2}$ and NaOMe at $-78^{\circ} \mathrm{C}$, gives product V. The structure of U and V are
(a)$\mathrm{U}=$ 
$\mathrm{V}=$ 
$\mathrm{V}=$ (b)$\mathrm{U}=$ 
V = 
V = (c)$\mathrm{U}=$ 
$\mathrm{V}=$ 
$\mathrm{V}=$ (d)
V = 
V = Answer
Answer: D ✓ checked by 4AB · confidence medium
Explanation
Syn hydroboration puts H and B cis, giving U. The Zweifel reaction (I₂/NaOMe) proceeds with net inversion of alkene geometry, so in V the cyclohexyl group ends up cis to the methyl that was trans to boron (d).
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