Chapter 14, Problem 14.62P

Interpretation Introduction

Interpretation:

Which the two, pyridine or pyrrole, is a stronger nucleophile in an ${\text{S}}_{\text{N}}\text{2}$ reaction is to be explained.

Concept introduction:

An electron-rich species such as one containing an atom with a lone pair acts as a nucleophile. Its strength as a nucleophile depends on how easily it can donate that lone pair. If the lone pair is involved in resonance, as a part of a conjugated $\text{π}$ system, then it is not easily available for donation in an ${\text{S}}_{\text{N}}\text{2}$ reaction. The species is then a weak nucleophile compared to a similar species in which the lone pair is not involved in resonance. For the lone pair to be involved in resonance, it must reside in a pure p orbital of an ${\text{sp}}^2$ hybridized atom