Question: How do the mechanisms of the following reactions differ?

In nucleophilic aromatic substitution reactions, the ring has a leaving group that is replaced by a nucleophile.Nucleophilic aromatic substitution of pyridine takes place at C-2 or C-4 because addition to these positions leads to the most stable intermediate. Only when addition occurs to these positions, a resonance contributor obtained that has the greatest electron density on nitrogen, the most electronegative elementof the ring atoms.

It involves two steps:

1. The nucleophile added to the ring carbon that is attached to the leaving group.
2. The leaving group is eliminated in the last step of the reaction.

TheS_N2 reaction is a nucleophilic substitution reaction where bond is broken and other is form simultaneously. Two reacting species involved in the rate determining step of the reaction. The termS_N2 stands for substitution nucleophilic bimolecular.

This reaction follows two step nucleophilic aromatic substitution (S_NAr).

This reaction follows one step nucleophilic substitution reaction S_N2 reaction mechanism.

Mechanism of reaction (2)