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(pĭr`ĭdēn) or


(ăz`ēn), C5H5N, colorless, flammable, toxic liquid with a putrid odor. It melts at −42°C; and boils at 115.5°C;. Chemically, it is a heterocyclic aromatic tertiary amine (see under amino groupamino group,
in chemistry, functional group that consists of a nitrogen atom attached by single bonds to hydrogen atoms, alkyl groups, aryl groups, or a combination of these three. An organic compound that contains an amino group is called an amine.
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). Its molecule resembles that of benzene, one carbon-hydrogen unit in the benzene ring being replaced with a nitrogen molecule. It is miscible with water and with most organic solvents. Its aqueous solution is slightly alkaline. Pyridine is used as a solvent, as a denaturant for alcohol, and as a starting material in the synthesis of other compounds. Compounds that can be derived from pyridine include antihistamines and vitamins. Pyridine is obtained from bone oil or from coal tar by destructive distillation, which decomposes alkaloids that contain it. Alkaloids that contain pyridine include coniine, piperine (the alkaloid in pepper), and nicotine (present in tobacco); free pyridine is present in tobacco smoke.
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The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



a heterocyclic compound. Colorless liquid with a characteristic odor. Melting point, — 41.6°C; boiling point, 115.3°C; density, 0.9832 g/cm3 (at 20°C). The structural formula

Pyridine is a weak base that is miscible in all proportions with water and most organic solvents. It forms salts with acids as well as with alkyl halides (RX); the alkyl halide salts are called N-alkyl pyridinium salts and have the general formula C5H5N-RX. Pyridine also forms complexes with FeCl2, S02, S03, Br2, and H20. It is oxidized by peracids (RCOOOH)to give N-oxides.

Pyridine exhibits the properties of an aromatic compound, although—unlike benzene—it does not undergo electrophilic substitution readily: it is nitrated, sulfonated, and brominated only at about 300°C, primarily with the resultant formation of ss-derivatives. Nucleophilic substitution occurs more easily with pyridine than with benzene. For example, pyridine reacts with NaNH2 to give α-aminopyridine and with KOH to give a- hydroxypyridine. Pyridine is reduced by sodium in ethanol or by hydrogen over a nickel catalyst at 120°C to give piperidine. The pyridine ring can be cleaved by, for example, the action of bases on pyridinium salts to form glutaconic dialdehyde (HOCCH=CHCH2COH) or the corresponding glutaconic-dialdehyde derivative. The pyridine nucleus is a structural component of many alkaloids, vitamins, and drugs, including anabasine, nicotine, nicotinic acid, and nikethamide.

Pyridine is toxic, with a maximum permissible vapor concentration in the air of 0.0015 mg/l. Coal tar, which contains about 0.08 percent pyridine, is the major source. A mixture of pyridine and its homologues, the pyridine bases, are extracted with dilute sulfuric acid from the light and medium fractions of the tar oils in coal tar. After neutralization, the desired compounds are separated by distillation.

Pyridine is widely used in industrial organic synthesis as a solvent and in the production of dyes, pesticides, and drugs. Derivatives of pyridine, for example, 2-methyl-5-vinylpyridine, are used in the production of vinylpyridine lattices. Pyridine N-sulfur trioxide (C5H5N -S03) is a mild sulfonating agent.


The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.


(organic chemistry)
C5H5N Organic base; flammable, toxic yellowish liquid, with penetrating aroma and burning taste; soluble in water, alcohol, ether, benzene, and fatty oils; boils at 116°C; used as an alcohol denaturant, solvent, in paints, medicine, and textile dyeing.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
Synthesis of disperse dyes: Eight novels disperse dyes based on substituted pyridines and their derivatives, oxazine, carbooxyanilide and thiocarbamate were synthesized using substituted aryl amines as chromophores.
The peaks of the extract oil and the shale oil diesel distillate at 1606 [cm.sup.-1] may be assigned to the C=N skeleton vibration on the pyridine ring.
The pyridine derivatives were obtained in good yield using solvent and catalyst-free condition under the fusion condition.
From the biological activity investigation, we observed that the antitumor activity of compounds 1 and 2 advanced greatly when organic ligands pyridine and Schiff bases were in coordination with Co ion.
Technavio's analysts forecast the global pyridine market to grow at a CAGR of 7.45% during the period 2016-2020.
Figure 1 shows the FT-Raman spectra of the three aminophosphonate derivatives of pyridine: [alpha]-Pyr, [beta]-Pyr, and [gamma]-Pyr, in the solid state in the spectral ranges between 3200-2800 and 1800-400 [cm.sup.-1].
The results obtained from various physicochemical and spectral techniques suggest that the adducts of bis(O-ethyldithiocarbonato)copper(II) with substituted pyridines have 1: 1 stoichiometry with square pyramidal geometry around copper(II) ion.
Keywords: Aminoalkyl pyridine alkaloids, Antimicrobial, Cytotoxicity, Marine sponges, Callyspongia crassa
Behzadi, "A simple, efficient, one-pot three-component domino synthesis of Hantzsch pyridines under solvent-free condition," Journal of Heterocyclic Chemistry, vol.
The ligand exhibits hydroxyl proton ([H.sub.a]) appearing at [delta] 15.68 ppm, the aromatic pyridine proton ([H.sub.b]) appearing at [delta] 9.97 ppm, [H.sub.c] appearing at [delta] 8.30 ppm, [H.sub.d] appearing at [delta] 6.89 ppm, methyl proton ([H.sub.e]) appearing at [delta] 2.49 ppm, and aromatic and heteroaromatic proton signals appearing at S 7.04-8.15 ppm.
Moreover, the increased heating rate results in an obvious and slight decrease in the relative abundance of pyridines (DBE = 4) with the highest abundance of [N.sub.1] class, and of those whose DBE is within the range of 5-10, respectively.
In first molecule the dihedral angle between the benzene ring A (C1C6) and the pyridine ring B (C9C13/N3) is 76.264 (103), in second molecule the dihedral angle between the benzene ring C (C14C19) and the pyridine ring D (C22C26/N6) is 62.395 (082 ) and in third molecule the dihedral angle between the benzene ring E (C27C32) and the pyridine ring F (C35C39/N9) is 72.491 (98).