MCQ Detailed View

Pyridine is a six-membered aromatic heterocyclic compound with one nitrogen atom in the ring. The nitrogen atom in pyridine is sp² hybridized, which allows the ring to maintain planarity and aromaticity. In sp² hybridization, one s orbital mixes with two p orbitals to form three sp² hybrid orbitals. Two of these orbitals form sigma bonds with adjacent carbon atoms in the ring, and the third contains a lone pair of electrons.

The unhybridized p orbital of nitrogen overlaps with p orbitals of the carbon atoms, contributing to the delocalized π-electron system of the aromatic ring. This delocalization is essential for the aromatic stability of pyridine, similar to benzene. The lone pair of electrons on the nitrogen remains in an sp² orbital and does not participate in the aromatic π system. This distinguishes pyridine from pyrrole, where the nitrogen lone pair participates in the aromaticity.

Other options are incorrect. sp hybridization occurs in molecules with triple bonds or linear geometry, which is not the case for nitrogen in pyridine. sp³ hybridization occurs in saturated nitrogen compounds like amines, which have tetrahedral geometry. The nitrogen atom is always hybridized in pyridine; therefore, "It is not hybridized" is incorrect.

Understanding the hybridization of nitrogen is important in predicting reactivity, basicity, and chemical behavior. The sp² hybridized nitrogen in pyridine makes it less basic than aliphatic amines because the lone pair is localized in the plane of the ring and does not participate in delocalization. This knowledge is crucial for reactions such as electrophilic substitution and nucleophilic reactions in organic chemistry.