Chapter 21, Problem 21.44P

Interpretation Introduction

(a)

Interpretation:

The mechanism and the structure of the product of the nucleophilic addition-elimination reaction between pyridine and an acid chloride are to be drawn.

Concept introduction:

Pyridine is a moderately strong nucleophile as the lone pair of the nitrogen atom is not involved in resonance (and aromaticity). When it is used as a solvent in a nucleophilic addition-elimination reaction, it can compete with the reagent, adding to the carbonyl carbon of the substrate.

Interpretation Introduction

(b)

Interpretation:

Why the reaction involving pyridine does not interfere with the production of the desired amide product of the given reaction is to be explained.

Concept introduction:

Pyridine is a moderately strong nucleophile as the lone pair of the nitrogen atom is not involved in resonance (and aromaticity). When it is used as a solvent in a nucleophilic addition-elimination reaction, it can compete with the reagent, adding to the carbonyl carbon of the substrate. The product of the reaction has a positive charge on the nitrogen of the pyridine group and, therefore, is reactive toward nucleophilic addition-substitution reaction.