Chapter 9.5, Problem 21P

(a)

Interpretation Introduction

Interpretation:

Among the given compounds, the one which is more reactive in a ${\text{S}}_{\text{N}}\text{2}$ reaction has to be identified.

Concept Introduction:

Vinyl and aryl halides: (${\text{S}}_{\text{N}}\text{2}$ reaction)

Vinylic halides and aryl halides do not undergo ${\text{S}}_{\text{N}}\text{2}$ reaction. Because, as the nucleophile approaches the back side of the $s{p}^2$ carbon, it is repelled by the $\pi$ electrons of the double bond or the benzene ring.

(b)

Interpretation Introduction

Interpretation:

Among the given compounds, the one which is more reactive in a ${\text{S}}_{\text{N}}\text{2}$ reaction has to be identified.

Concept Introduction:

Vinyl and aryl halides: (${\text{S}}_{\text{N}}\text{2}$ reaction)

Vinylic halides and aryl halides do not undergo ${\text{S}}_{\text{N}}\text{2}$ reaction. Because, as the nucleophile approaches the back side of the $s{p}^2$ carbon, it is repelled by the $\pi$ electrons of the double bond or the benzene ring.