pyridine

Pyridine is a basic heterocyclic aromatic organic compound with the formula C5H5N. It consists of a six-membered ring with one nitrogen atom, is structurally related to benzene, and is planar and aromatic.

Pyridine is a colorless, flammable liquid with a distinctive, unpleasant odor. It is miscible with water and with most organic solvents. It boils at about 115°C and freezes at around -41°C. The conjugate acid has a pKa near 5.25, reflecting moderate basicity; as a result it readily forms pyridinium salts and serves as a versatile base and ligand in coordination chemistry.

Pyridine is a common industrial reagent and building block. It is used as a solvent for polymers and resins and as a precursor in the manufacture of agrochemicals, vitamins (notably niacin), pharmaceuticals, and specialty chemicals. It also serves as a ligand in metal complexes and as an acid scavenger and catalyst component in various reactions.

Production of pyridine is on a large scale. Historically it was obtained from coal tar; today it is produced from coal-tar–derived streams and refinery byproducts, often via catalytic oxidation and dehydrogenation steps of related heterocycles.

Safety: Pyridine is toxic and can irritate the skin, eyes, and respiratory tract. It is flammable and should be handled in well‑ventilated areas with appropriate protective equipment.

Occurrence: It occurs only in trace amounts in some tobacco smoke and other natural materials.