Chapter 26, Problem 26.12P

Interpretation Introduction

Interpretation:

The aromatic substitution reaction of $\text{pyridine-N-oxide}$ takes place at $4-$ position rather than $3-$ position is to be explained by giving resonance structure of carbocation intermediate formed.

Concept Introduction:

The aromatic electrophilic substitution reaction takes place at the position which is more resonance stabilized. The resonance structure which has more charge will be less stable. Also more the separation between the charged atoms, more will be the stability of resonance structure. The more stable intermediate will form the product.