JEE PYQ: Hydrocarbons Question 8
Question 8 - 2021 (24 Feb Shift 1)
What is the major product formed by HI on reaction with $(\text{CH}_3)_2\text{C}=\text{CH}-\text{CH}(\text{CH}_3)_2$?
(1) $\text{CH}_3-\text{C}(\text{CH}_3)(\text{H})-\text{CH}(-\text{CH}_2\text{I})-\text{CH}_3$
(2) $\text{CH}_3-\text{C}(\text{CH}_3)(\text{I})-\text{CH}(-\text{CH}_3)-\text{CH}_3$
(3) $\text{CH}_3-\text{C}(\text{CH}_3)(\text{I})-\text{CH}(-\text{CH}_3)-\text{CH}_3$ (different regiochemistry)
(4) Ring-opened product
Show Answer
Answer: (3)
Solution
HI adds across the double bond following Markovnikov’s rule. $\text{H}^+$ adds to give the more stable tertiary carbocation: $(\text{CH}_3)_3\text{C}^+-\text{CH}(\text{CH}_3)_2$. Then $\text{I}^-$ attacks to give the product. After 1,2-H shift the most stable carbocation forms, giving the major product.
BETA
