Question

Does pyridine undergo nucleophilic aromatic substitution reactions? If no, why not. If yes, on what position does the substitution occur? Use resonance contributors to justify your answer.(15 points) b) Draw the tautomers of 2-hydroxypyridine and 4-hydroxypyridine (5 points)

Answer 1

Explanation:

Part a

Pyridine is an aromatic heterocyclic compound and undergoes nucleophilic aromatic substitution reaction at 2 and 4 positions.

This is because, when a  nucleophile attack pyridine at 2 and 4 positions, the anoin formed is stabilized. In the anion formed is tabilized by resonance and also negative charge is present at electronegative atom, nitrogen.

If the nucleophile attack at 3 position, the anion formed is not as stable as anions formed when nucleophile attach at 2 and 4 positions. This is because negative charge is not present at the nitrogen atom.

Part b:

Tautomers are structural isomers of each others formed by migration atom within the molecule. Tautomers exist in equilibrium with each other.

Tautomers of 2-Hydroxypyridine and 4-Hydroxypyrine are given in the attachment.