Chemicals - Pyridines

Pyridine is a colorless and highly flammable chemical compound with the molecular formula C5H5N. It belongs to the heterocyclic parent systems and forms the simplest azine, which consists of a six-membered ring with five carbon atoms and one nitrogen atom. The name azine is derived from the systematic Hantzsch-Widman nomenclature, according to which pyridine is called azine. By analogy with benzene, the name azabenzole is also occasionally encountered. In 1849, pyridine was first described by the Scottish chemist and physician Thomas Anderson, who was investigating the constituents of bone oil. Two years later, Anderson isolated pyridine in pure form for the first time by fractional distillation of the oil. In the chemical industry, pyridine is both a major synthetic building block for drug or herbicide production and a common solvent for chemical reactions. Tens of thousands of tons of the compound are produced annually worldwide, and much of it is reused in the chemical industry. Historically, pyridine was obtained from tar or as a by-product of coal gasification; however, due to increased demand, these methods have given way to more economical synthetic processes over the years. Pyridine meets the Hückel criteria for aromaticity and exhibits typical heteroaromatic properties. Its reactivity to electrophilic substitutions is significantly lower than that of the homoaromatic analogue benzene, whereas nucleophilic substitutions occur more frequently.