Pyridine

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{acid, form, water}

-41.6 °C, 232 K, -43 °F

115.2 °C, 388 K, 239 °F

Pyridine is a heterocyclic organic compound with the chemical formula C5H5N. It is structurally related to benzene, with one CH group replaced by a nitrogen atom. It is used as a precursor to agrochemicals and pharmaceuticals and is also an important solvent and reagent. It is a colorless liquid with a distinctive, unpleasant fish-like odor. The pyridine ring occurs in many important compounds, including the vitamins nicotinamide and pyridoxal.

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Preparation and occurrence

Pyridine was originally industrially produced by extraction from coal tar. It is currently synthesized from formaldehyde, ammonia, and acetaldehyde:

This process (Chichibabin pyridine synthesis) involves the intermediacy of acrolein. An estimated 26,000 tons were produced worldwide in 1989[citation needed]. Condensations of ammonia sources and related unsaturated carbon sources affords alkyl- and aryl-substituted pyridines, e.g. monomethyl compounds (picolines), dimethyl compounds (lutidines), and trimethyl derivatives (collidines).[4] Pyridine occurs in numerous plants, although this was mostly recorded just by smell. Goris and Larsonneau[5] did show definite evidence of its presence in belladonna leaves, while Kuhn and Schäfer[6][7] of its presence in the roots of the same plant.

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