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| Pyridine | |
|---|---|
| Name | Pyridine |
| Formula | C5H5N |
| Molar mass | 79.10 g·mol−1 |
| Appearance | colorless liquid |
| Density | 0.981 g·cm−3 |
| Bp | 115 °C |
| Mp | −42 °C |
| Solubility | miscible with water |
| CAS | 110-86-1 |
Pyridine is an aromatic heterocyclic organic compound consisting of a six-membered ring with five carbon atoms and one nitrogen atom. It is a basic, polar solvent and a key building block in the synthesis of pharmaceuticals, agrochemicals, and fine chemicals. Pyridine's properties and reactivity make it central to industrial organic chemistry and to research in synthetic methodology and heterocyclic chemistry.
The molecule features a planar, aromatic Hückel-compliant six-membered ring analogous to Benzene, with the lone pair on the ring nitrogen orthogonal to the π system, imparting basicity and coordination behavior comparable to heterocycles studied by August Wilhelm von Hofmann and techniques used in X-ray crystallography by investigators such as Dorothy Hodgkin. Crystal structures illustrate bond alternation similar to patterns reported for Nicotinic acid derivatives and complexes characterized by groups at institutions like Max Planck Society and University of Cambridge. The compound has a refractive index measured in physical chemistry laboratories including those at National Physical Laboratory (United Kingdom), and its vapor pressure features in thermodynamic compilations maintained by agencies such as the National Institute of Standards and Technology. Optical rotation is negligible due to achirality, while dipole moment and dielectric constant data are routinely compared to solvents cataloged by companies like Merck Group and Sigma-Aldrich.
Industrial production historically follows methods developed in the 19th and 20th centuries, including dehydrogenation of methylpyridines produced from coal-tar distillation pioneered during the era of Friedrich Wöhler and refined alongside processes at firms like BASF and Dow Chemical Company. Modern syntheses use catalytic routes inspired by work from Ryōji Noyori-era homogeneous catalysis and heterogeneous catalysts from research at Imperial College London and ETH Zurich. Laboratory methods include condensation reactions analogous to the Hantzsch pyridine synthesis and the Bohlmann–Rahtz pyridine synthesis, which are routinely employed in academic groups at University of Oxford and Harvard University. C–N bond-forming approaches using cross-coupling methods developed by awardees such as Akira Suzuki and Ei-ichi Negishi are applied to substituted derivatives, with scale-up techniques adapted by chemical manufacturers like Lonza and Pfizer.
As a Lewis base and nucleophilic heteroarene, pyridine undergoes electrophilic and nucleophilic transformations studied in the context of methodologies from research groups led by E. J. Corey and Karl Barry Sharpless. Electrophilic substitution is deactivated relative to Benzene, favoring substitution at the 3-position as discussed in treatises by Linus Pauling and textbooks used at Massachusetts Institute of Technology. N-oxidation to pyridine N-oxide and N-alkylation to pyridinium salts are central steps in synthetic sequences employed in laboratories including those of Novartis and GlaxoSmithKline. Metal coordination to the nitrogen is exploited in complexes characterized by Jean-Marie Lehn and applied in catalysis described in work from Stanford University and California Institute of Technology. Reductions to piperidine and oxidations to nicotinic acid derivatives intersect with research by Robert Burns Woodward and industrial processes utilized by DuPont.
Pyridine serves as a precursor to agrochemicals developed by companies such as Syngenta and Bayer AG, and to pharmaceuticals synthesized by corporations including Roche and Merck & Co.. It is a solvent and base in organic synthesis protocols common in academic laboratories at Yale University and Princeton University, and a ligand scaffold in coordination compounds explored at University of California, Berkeley. Pyridine derivatives are core motifs in vitamins like Niacin (vitamin B3) studied in nutritional research at institutions such as Johns Hopkins University and in active pharmaceutical ingredients patented by firms like Johnson & Johnson. It is used in dye chemistry with historical links to companies like DuPont and applications in materials science investigated at IBM Research and Bell Labs.
Pyridine is toxic and flammable; occupational exposure limits are set by regulatory bodies such as the Occupational Safety and Health Administration and European Chemicals Agency. Toxicology studies conducted at institutions including National Institutes of Health and Centers for Disease Control and Prevention document effects on the central nervous system and hepatic metabolism, with metabolic pathways examined in research from Scripps Research and Karolinska Institute. Environmental fate, biodegradation, and remediation strategies have been developed by agencies like the Environmental Protection Agency and research centers at University of Waterloo and ETH Zurich. Waste treatment and emission controls are practiced by chemical producers such as ExxonMobil and Shell to meet standards enforced under laws like the Clean Air Act.
Characterization employs NMR with chemical shifts cited in spectral databases maintained by American Chemical Society journals and groups at Bruker and JEOL. Infrared spectroscopy, mass spectrometry, and UV–visible spectroscopy data appear in compilations from Royal Society of Chemistry and analytical labs at National Institutes of Health. X-ray crystallography performed at facilities such as European Synchrotron Radiation Facility and Diamond Light Source provides structural confirmation for derivatives synthesized in research from University of Tokyo and Seoul National University. Chromatographic separation techniques using columns from Agilent Technologies and detectors from Shimadzu are standard for purity assessment in pharmaceutical quality control at Pfizer and regulatory submissions to agencies like the Food and Drug Administration.
Category:Organonitrogen compounds