JEE PYQ: Hydrocarbons Question 14
Question 14 - 2020 (02 Sep Shift 1)
Which of the following compounds will show retention in configuration on nucleophilic substitution by $\text{OH}^-$ ion?
(1) $\text{CH}_3-\text{C}(-\text{Br})(-\text{H})-\text{C}6\text{H}{13}$
(2) $\text{CH}_3-\text{CH}(-\text{Br})-\text{C}_6\text{H}_5$
(3) $\text{CH}_3-\text{CH}(-\text{Br})-\text{CH}_3$
(4) $\text{CH}_3-\text{CH}(-\text{CH}_2\text{Br})-\text{C}_2\text{H}_5$
Show Answer
Answer: (4)
Solution
$\text{CH}_3-\text{CH}(-\text{CH}_2\text{Br})-\text{C}_2\text{H}5 \xrightarrow{\text{S}\text{N}1}$ $\text{CH}_3-\text{CH}^+-\text{C}_2\text{H}_5$ then 1,2-H shift gives tertiary carbocation $\rightarrow$ $\text{CH}_3-\text{C}(-\text{OH})(-\text{C}_2\text{H}_5)-\text{CH}_3$. Retention of configuration occurs due to neighboring group participation.
BETA
