Q. In the nucleophilic substitution reactions $\left( S_{N}2or\ S_{N}1 \right)$, the reactivity of alkyl halides follows the sequence
A) R-I>R-Br>R-Cl>R-F
B) R-Cl>R-F>R-Br>R-I
C) R-F>R-Cl>R-Br>R-I
D) R-I>R-F>R-Cl>R-Br
Explanation
(a)
The correct order of reactivity is
$\ \ \ \ \ RI > RBr > RCl > RF\$
It is due to fact, that weaker the base, better it will be the leaving group.
Hence, $I^{-}$ is the best leaving group.
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.