Introduction about pyridine ring. py ridine, any of a class of organic compounds of the aromatic heterocyclic series characterized by a six-membered ring structure composed of five carbon atoms and one nitrogen atom. The simplest member of the pyridine family is pyridine itself, a compound with molecular formula C5H5N It is structurally related tobenzene, with one methine group (=CH−) replaced by a nitrogen atom. The pyridine ring occurs in many important compounds, including azines and the vitamins niacin and pyridoxal.
Pyridine is used as a solvent and is added to ethyl alcohol to make it unfit for drinking. It is converted to such products as sulfapyridine, a drug active against bacterial and viral infections; pyribenzamine and pyrilamine, used as antihistaminic drugs;
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Chemical properties
Pyridine is miscible with water and virtually all organic solvents.[10] It is weakly basic, and with hydrochloric acid it forms a crystalline hydrochloride salt that melts at 145–147 °C.[25] Most chemical properties of pyridine are typical of aheteroaromatic compound
Molecular properties
Pyridine has a conjugated system of six π electrons that are delocalized over the ring. The molecule is planar and, thus, follows the Hückel criteria for aromatic systems. In contrast to benzene, the electron density is not evenly distributed over the ring, reflecting the negative inductive effect of the nitrogen atom. For this reason, pyridine has a dipole moment and a weaker resonant stabilization than benzene (resonance energy) Production[edit]
Chichibabin synthesis
In its general form, the reaction can be described as a condensation reaction of aldehydes, ketones, α,β-unsaturated carbonyl compounds, or any combination of the above, in ammonia or ammonia derivatives.[66] In particular, unsubstituted pyridine is produced from formaldehyde and acetaldehyde
Formation of acrolein from acetaldehyde and