PYQ NEET- Organic Chemistry Some Basic Principles L-4

Question: Predict the order of reactivity of the following four isomers towards $\mathrm{S}_{\mathrm{N}} 2$ reaction.#

(I) $\mathrm{CH}_3 \mathrm{CH}_2 \mathrm{CH}_2 \mathrm{CH}_2 \mathrm{Cl}$ (II) $\mathrm{CH}_3 \mathrm{CH}_2 \mathrm{CH}(\mathrm{Cl}) \mathrm{CH}_3$ (III) $\left(\mathrm{CH}_3\right)_2 \mathrm{CHCH}_2 \mathrm{Cl}$ (IV) $\left(\mathrm{CH}_3\right)_3 \mathrm{CCl}$

A) (IV) $>$ (II) $>$ (III) $>$ (I)

B) (IV) $>$ (III) $>$ (II) $>$ (I)

C) (I) $>$ (II) $>$ (III) $>$ (IV)

D) (I) $>$ (III) $>$ (II) $>$ (IV)

Answer: (I) $>$ (III) $>$ (II) $>$ (IV)#

Solution:#

• Lesser the steric hinderance on halide carbon, more will be the reactivity of alkyl halide towards $\mathrm{S}_{\mathrm{N}} 2$ reaction.
• So correct order towards $\mathrm{S}_{\mathrm{N}} 2$ reactivity is :