JEE PYQ: Hydrocarbons Question 19
Question 19 - 2020 (03 Sep Shift 1)
The mechanism of $\text{S}_\text{N}1$ reaction is given as:
$\text{R}-\text{X} \rightarrow \text{R}^+\text{X}^- \rightarrow \text{R}^+|\text{X}^- \rightarrow \text{R}-\text{Y} + \text{X}^-$
A student writes general characteristics based on the given mechanism as:
(a) The reaction is favoured by weak nucleophiles. (b) $\text{R}^+$ would be easily formed if the substituents are bulky. (c) The reaction is accompanied by racemization. (d) The reaction is favoured by non-polar solvents.
Which observations are correct?
(1) (a) and (b)
(2) (a) and (c)
(3) (a), (b) and (c)
(4) (b) and (d)
Show Answer
Answer: (3)
Solution
Above reaction is $\text{S}\text{N}1$ reaction as it proceeds via formation of carbocation. Polar protic solvent is more suitable for $\text{S}\text{N}1$ and so racemisation takes place. (d) is incorrect — polar solvents favour $\text{S}_\text{N}1$.
BETA
