Q. Which of the following is least reactive in a nucleophilic substitution reaction?
A) $\left( CH_{3} \right)_{3}C - Cl$
B) $CH_{2} = CHCl$
C) $CH_{3}CH_{2}Cl$
D) $CH_{2} = CHCH_{2}Cl$
Explanation
(b)
Chlorine of vinyl chloride $(CH_{2} = CHCl)$ is non-reactive (less reactive) towards nucleophile in nucleophilic substitution reaction because it shows the following resonating structure due to +M effect of $–Cl$ atom.
[image:12_image394.emf]
In structure II, Cl-atom have positive charge and partial double bond character with C of vinyl group, so it is more tightly attracted towards the nucleus and it does not get replaced by nucleophile in $S_{N^{-}}$ reaction.
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.