Pyridine is an organic compound with a heterocyclic basic nature and a chemical formula of C5H5N. Its structure is similar to that of benzene, except for the substitution of a nitrogen atom for a methine group (=CH−).

Pyridine ring is found in numerous essential compounds such as agrochemicals, pharmaceuticals, and vitamins. In the past, coal tar was the source for producing pyridine.

Pyridine differs from benzene in that its ring does not have an even distribution of electron density due to the negative inductive effect of the nitrogen atom. As a result, pyridine possesses a dipole moment and has a weaker resonant stabilization compared to benzene, as evidenced by its resonance energy of 117 kJ·mol-1 (as opposed to benzene’s 150 kJ·mol-1).

Pyridine, due to the presence of an electronegative nitrogen atom in its ring, exhibits a lower tendency to undergo electrophilic aromatic substitution reactions compared to benzene derivatives. Its reactivity, instead, bears a resemblance to that of nitrobenzene.

In the pyridine molecule, the ring atoms have undergone sp2 hybridization, while the nitrogen atom utilizes its unhybridized p orbital to participate in the π-bonding aromatic system. The lone pair of electrons resides in an sp2 orbital and extends outward from the ring in the same plane as the σ bonds.