Arrange the following in correct order towards $\mathrm{S}_{\mathrm{N}} 2$ reaction.
Arrange the following in correct order towards $\mathrm{S}_{\mathrm{N}} 2$ reaction.
III $>$ I $>$ IV $>$ II
III $>$ IV $>$ I $>$ II
I $>$ II $>$ III $>$ IV
I $>$ III $>$ II $>$ IV
Solution
(a) $\mathrm{S}_{\mathrm{N}} 2$ reactivity depends on steric crowding at the $\alpha$ - carbon and the $\mathrm{C}-\mathrm{X}$ bond strength.
Steric crowding $\uparrow, \mathrm{S}_{\mathrm{N}} 2$ reactivity $\downarrow$
C-X bond strength $\uparrow, \mathrm{S}_{\mathrm{N}} 2$ reactivity $\downarrow$
Thus, the order of reactivity towards $\mathrm{S}_{\mathrm{N}} 2$ will be :-
