JEE PYQ: Haloalkanes And Haloarenes Question 4
Question 4 - 2021 (24 Feb Shift 1)
The product formed in the first step of the reaction of:
$\text{CH}_3-\text{CH}_2-\text{CH}(-\text{Br})-\text{CH}_2-\text{CH}(-\text{Br})-\text{CH}_3$
with excess $\text{Mg}/\text{Et}_2\text{O}$ (Et = $\text{C}_2\text{H}_5$) is:
(1) $\text{CH}_3-\text{CH}_2-\text{CH}=\text{CH}-\text{CH}(-\text{CH}_3)$ (elimination product)
(2) $\text{CH}_3-\text{CH}_2-\text{CH}(-\text{MgBr})-\text{CH}_2-\text{CH}(-\text{CH}_3)$ (Grignard at both positions)
(3) $\text{CH}_3\text{CH}_2-\text{CH}(-\text{MgBr})-\text{CH}_2-\text{CH}(-\text{MgBr})-\text{CH}_3$
(4) Cyclopropane derivative
Show Answer
Answer: (3)
Solution
With excess Mg/Et$_2$O, both C-Br bonds react to form a bis-Grignard reagent: $\text{CH}_3\text{CH}_2-\text{CH}(-\text{MgBr})-\text{CH}_2-\text{CH}(-\text{MgBr})-\text{CH}_3$.
BETA
