JEE PYQ: Haloalkanes And Haloarenes Question 18
Question 18 - 2019 (10 Apr Shift 1)
The major product of the following reaction is:
$\text{CH}_3-\text{C}(\text{CH}_3)(\text{H})-\text{CHBr}-\text{CH}_3 \xrightarrow{\text{CH}_3\text{OH}}$
(1) $\text{CH}_3-\text{C}(\text{CH}_3)=\text{CH}-\text{CH}_2$ (elimination)
(2) $\text{CH}_3-\text{C}(\text{CH}_3)=\text{CHCH}_3$ (elimination, Saytzeff)
(3) $\text{CH}_3-\text{C}(\text{CH}_3)(\text{OCH}_3)-\text{CH}_2\text{CH}_3$ (substitution with rearrangement)
(4) $\text{CH}_3-\text{C}(\text{CH}_3)(\text{H})-\text{CH}(\text{OCH}_3)-\text{CH}_3$ (substitution without rearrangement)
Show Answer
Answer: (3)
Solution
$\text{CH}3\text{OH}$ is a weak nucleophile, so $\text{S}\text{N}1$ pathway operates. Secondary carbocation rearranges to more stable tertiary carbocation: $\text{CH}_3-\overset{+}{\text{C}}(\text{CH}_3)_2-\text{CH}_2-\text{CH}_3$. Then $\text{CH}_3\text{OH}$ attacks to give the substitution product with rearrangement.
BETA
