JEE Main 2022 · 27 Jun · Shift 2 · Chemistry Q73

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ChemistrySingle correct+4 / -1Question 73 of 90

What will be the major product of following sequence of reactions?
$\text{n-Bu}\text{-}\mathrm{C{\equiv}CH}\xrightarrow[\text{(ii) Lindlar cat, H}_2]{\text{(i) n-BuLi, n-C}_5\text{H}_{11}\text{Cl}}$

Alkene with n-Bu on both carbons of the C=C and C5H11 on one (trisubstituted)

Alkene: one carbon bears n-Bu above and C5H11 below-left; the other bears n-Bu below-right.

Alkene with n-Bu and C5H11 on one carbon and n-Bu on the other

Alkene: n-Bu at lower left on one carbon; the other carbon bears n-Bu above and C5H11 below.

cis-

\mathrm{C_5H_{11}CH{=}CH\text{-}n\text{-}Bu}

(Z)

cis-Undec-5-ene: C5H11 and n-Bu on the same side of the C=C.

trans-

\mathrm{C_5H_{11}CH{=}CH\text{-}n\text{-}Bu}

(E)

trans-Undec-5-ene: C5H11 and n-Bu on opposite sides of the C=C.

Answer and worked solution

Official answer: C

Alkylation. n-BuLi forms the acetylide, which displaces Cl from $\mathrm{C_5H_{11}Cl}$ : $\mathrm{n\text{-}Bu\text{-}C{\equiv}C\text{-}C_5H_{11}}$ .

Lindlar hydrogenation gives the cis alkene.

(C)

Topics:Alkynes Alkenes

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JEE Main 2022 · 27 Jun · Shift 2, Chemistry question 73