Pyridine Formula

Pyridine is structurally related to the benzene (C\[_{6}\]H\[_{6}\]) compound, with a nitrogen atom replacing a single methine group. Both the structural and chemical formula for pyridine is given below.

Structural Formula for Pyridine

As stated above, pyridine is structurally the same as benzene having a nitrogen atom by replacing one of the =CH− groups. The molecular formula of pyridine is given as C\[_{5}\]H\[_{5}\]N and the pyridine structure formula or pyridine chemical formula is represented as follows:

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Pyridine Chemical Formula

Pyridine contains 5 hydrogen atoms, 5 carbon atoms, and a nitrogen atom. It is a 6-atom heterocyclic organic compound and contains a molar mass of 70.0999 g/mol. The chemical formula for pyridine is C\[_{5}\]H\[_{5}\]N.

Pyridine Properties

Physical Properties

The molecular electric dipole moment is given as 2.2 debyes. Pyridine is defined as diamagnetic and contains a diamagnetic susceptibility of −48.7 × 10\[^{-6}\] cm\[^{3}\]·mol\[^{-1}\]. The standard enthalpy of the formation is given as 100.2 kJ·mol\[^{-1}\] in the liquid phase and as 140.4 kJ·mol\[^{-1}\] in the gas phase.

Pyridine looks colorless to the yellow liquid holding a fish-like odor. It is mildly flammable, basic, and toxic to humans. There are many uses of pyridine and a few of the notable ones are in pharmaceuticals, dental care products, in paints and dyes, as a sulfonating and reducing agent, and more.

Chemical Properties

Due to the electronegative nitrogen in the pyridine ring, the molecule is said to be relatively electron deficient. Therefore, it enters less readily into the electrophilic aromatic substitution reactions compared to benzene derivatives. Correspondingly, the pyridine compound is more prone to nucleophilic substitution, as evidenced by the ease of metalation by the strong organometallic bases.

Pyridine reactivity may be differentiated for three chemical groups. With the electrophiles, electrophilic substitution occurs where the pyridine expresses aromatic properties. With the nucleophiles, pyridine reacts at the positions of 2 and 4 and hence behaves the same as carbonyls or imines. The reaction with several Lewis acids results in addition to the nitrogen atom of pyridine that is the same as the tertiary amines’ reactivity. The ability of pyridine, including its derivatives, to oxidize by forming amine oxides (N-oxides) is also given as a feature of tertiary amines.

Radical Reactions

Pyridine supports a radical reaction series, which is used in its dimerization to the bipyridines. Pyridine’ radical dimerization with Raney nickel or elemental sodium selectively yields or 2,2'-bipyridine or 4,4'-bipyridine, which are the essential precursor reagents in the chemical industry. One of the named reactions involving the free radicals is given as the Minisci reaction. It may produce 2-tert-butyl pyridine upon reacting the pyridine compound with pivalic acid, ammonium, and silver nitrate in sulfuric acid with a yield of 97%.