pyridine - wikipedia, the free encyclopedia

7/22/2019 Pyridine - Wikipedia, The Free Encyclopedia

1/15

6/20/13 Pyridine - Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Pyridine 1/15

Pyridine

Pyridine

AzineAzabenzene

Identifiers

CAS number 110-86-1

PubChem 1049

ChemSpider 1020

UNII NH9L3PP67S

EC number 203-809-9

KEGG C00747

ChEBI CHEBI:16227

ChEMBL CHEMBL266158

Jmol-3D images Image 1

(http://chemapps.stolaf.edu/jmol/jmol.php?

model=c1ccncc1)

Properties

Molecular formula C5H5N

Molar mass 79.10 g mol1

Appearance colorless liquid

Density 0.9819 g/mL[1]

PyridineFrom Wikipedia, the free encyclopedia

Pyridineis a basic heterocyclic organic compound with the chemicalformula C5 H5 N. It is structurally related to benzene, with one methinegroup (=CH-) replaced by a nitrogen atom. The pyridine ring occurs inmany important compounds, including azines and the vitamins niacin and

pyridoxal.

Pyridine was discovered in 1849 by the Scottish chemist ThomasAnderson as one of the constituents of bone oil. Two years later,Anderson isolated pure pyridine through fractional distillation of the oil. Itis a colorless, highly flammable, weakly alkaline, water-soluble liquid witha distinctive, unpleasant fish-like odor.

Pyridine is used as a precursor to agrochemicals and pharmaceuticals andis also an important solvent and reagent. Pyridine is added to ethanol tomake it unsuitable for drinking (see denatured alcohol). It is used in the invitro synthesis of DNA,[6] in the synthesis of sulfapyridine (a drug against

bacterial and viral infections), antihistaminic drugs tripelennamine andmepyramine, as well as water repellents, bactericides and herbicides.Some chemical compounds, although not synthesized from pyridine,contain its ring structure. They include B vitamins niacin and pyridoxal, ananti-tuberculosis drug isoniazid, nicotine and other nitrogen-containing

plant products.[7] Historically, pyridine was produced from coal tar andas a by-product of the coal gasification. However, increased demand for

pyridine resulted in the developmentof more economical methods ofsynthesis from acetaldehyde and ammonia, and more than 20,000 tonnes

per year are manufactured worldwide.

Contents

1 Properties1.1 Physical properties1.2 Chemical properties

1.2.1 Molecular properties2 History3 Occurrence4 Nomenclature5 Production

5.1 Chichibabin synthesis5.2 Dealkylation of alkylpyridines

5.3 Hantzsch pyridine synthesis5.4 Bnnemann cyclization5.5 Other methods5.6 Biosynthesis

6 Reactions6.1 Electrophilic substitutions6.2 Nucleophilic substitutions6.3 Radical reactions6.4 Reactions on the nitrogen atom6.5 Hydrogenation and reduction

7 Applications8 Hazards

9 Health issues10 See also11 References12 Bibliography13 External links

IUPAC name

Other names

SMILES

InChI
https://en.wikipedia.org/wiki/Pyridine#External_linkshttps://en.wikipedia.org/wiki/Pyridine#See_alsohttps://en.wikipedia.org/wiki/Molecular_formulahttps://en.wikipedia.org/wiki/Pyridine#Hazardshttps://en.wikipedia.org/wiki/Pyridine#Hazardshttps://en.wikipedia.org/wiki/Pyridine#Hazardshttps://en.wikipedia.org/wiki/Pyridine#Hazardshttps://en.wikipedia.org/wiki/Pyridine#Applicationshttps://en.wikipedia.org/wiki/Pyridine#Reactions_on_the_nitrogen_atomhttp://chemapps.stolaf.edu/jmol/jmol.php?model=c1ccncc1https://en.wikipedia.org/wiki/Pyridine#Reactionshttps://en.wikipedia.org/wiki/ChEMBLhttps://en.wikipedia.org/wiki/Pyridine#Biosynthesishttps://en.wikipedia.org/wiki/Pyridine#B.C3.B6nnemann_cyclizationhttps://en.wikipedia.org/wiki/EC_number_(chemistry)http://esis.jrc.ec.europa.eu/lib/einecs_IS_reponse.php?genre=ECNO&entree=203-809-9https://en.wikipedia.org/wiki/Pyridine#Hantzsch_pyridine_synthesishttps://en.wikipedia.org/wiki/Unique_Ingredient_Identifierhttp://fdasis.nlm.nih.gov/srs/srsdirect.jsp?regno=NH9L3PP67Shttps://en.wikipedia.org/wiki/Pyridine#Chichibabin_synthesishttps://en.wikipedia.org/wiki/Pyridine#Occurrencehttps://en.wikipedia.org/wiki/Pyridine#Historyhttps://en.wikipedia.org/wiki/Pyridine#Molecular_propertieshttps://en.wikipedia.org/wiki/Pyridine#Physical_propertieshttps://en.wikipedia.org/wiki/Pyridine#Physical_propertieshttps://en.wikipedia.org/wiki/Pyridine#Physical_propertieshttps://en.wikipedia.org/wiki/File:Pyridine_sample.jpghttps://en.wikipedia.org/wiki/File:Pyridine_sample.jpghttps://en.wikipedia.org/wiki/Acetaldehydehttps://en.wikipedia.org/wiki/Ammoniahttps://en.wikipedia.org/wiki/Tonnehttps://en.wikipedia.org/wiki/File:Pyridine_sample.jpghttps://en.wikipedia.org/wiki/Coal_gasificationhttps://en.wikipedia.org/wiki/File:Pyridine_sample.jpghttps://en.wikipedia.org/wiki/Pyridine#cite_note-brit-7https://en.wikipedia.org/wiki/Coal_tarhttps://en.wikipedia.org/wiki/File:Pyridine_sample.jpghttps://en.wikipedia.org/wiki/B_vitaminshttps://en.wikipedia.org/wiki/Niacinhttps://en.wikipedia.org/wiki/Pyridoxalhttps://en.wikipedia.org/wiki/File:Pyridine_sample.jpghttps://en.wikipedia.org/wiki/File:Pyridine_sample.jpghttps://en.wikipedia.org/wiki/Histamine_antagonisthttps://en.wikipedia.org/wiki/Tripelennaminehttps://en.wikipedia.org/wiki/Thomas_Anderson_(chemist)https://en.wikipedia.org/wiki/Methine_grouphttps://en.wikipedia.org/wiki/Nitrogenhttps://en.wikipedia.org/wiki/Methine_grouphttps://en.wikipedia.org/wiki/Methine_grouphttps://en.wikipedia.org/wiki/International_Chemical_Identifierhttps://en.wikipedia.org/wiki/Simplified_molecular-input_line-entry_systemhttps://en.wikipedia.org/wiki/International_Union_of_Pure_and_Applied_Chemistry_nomenclaturehttps://en.wikipedia.org/wiki/Pyridine#External_linkshttps://en.wikipedia.org/wiki/Pyridine#Bibliographyhttps://en.wikipedia.org/wiki/Pyridine#Referenceshttps://en.wikipedia.org/wiki/Pyridine#See_alsohttps://en.wikipedia.org/wiki/Pyridine#Health_issueshttps://en.wikipedia.org/wiki/Pyridine#Hazardshttps://en.wikipedia.org/wiki/Pyridine#Applicationshttps://en.wikipedia.org/wiki/Pyridine#Hydrogenation_and_reductionhttps://en.wikipedia.org/wiki/Pyridine#Reactions_on_the_nitrogen_atomhttps://en.wikipedia.org/wiki/Pyridine#Radical_reactionshttps://en.wikipedia.org/wiki/Pyridine#Nucleophilic_substitutionshttps://en.wikipedia.org/wiki/Pyridine#Electrophilic_substitutionshttps://en.wikipedia.org/wiki/Pyridine#Reactionshttps://en.wikipedia.org/wiki/Pyridine#Biosynthesishttps://en.wikipedia.org/wiki/Pyridine#Other_methodshttps://en.wikipedia.org/wiki/Pyridine#B.C3.B6nnemann_cyclizationhttps://en.wikipedia.org/wiki/Pyridine#Hantzsch_pyridine_synthesishttps://en.wikipedia.org/wiki/Pyridine#Dealkylation_of_alkylpyridineshttps://en.wikipedia.org/wiki/Pyridine#Chichibabin_synthesishttps://en.wikipedia.org/wiki/Pyridine#Productionhttps://en.wikipedia.org/wiki/Pyridine#Nomenclaturehttps://en.wikipedia.org/wiki/Pyridine#Occurrencehttps://en.wikipedia.org/wiki/Pyridine#Historyhttps://en.wikipedia.org/wiki/Pyridine#Molecular_propertieshttps://en.wikipedia.org/wiki/Pyridine#Chemical_propertieshttps://en.wikipedia.org/wiki/Pyridine#Physical_propertieshttps://en.wikipedia.org/wiki/Pyridine#Propertieshttps://en.wikipedia.org/wiki/Tonnehttps://en.wikipedia.org/wiki/Ammoniahttps://en.wikipedia.org/wiki/Acetaldehydehttps://en.wikipedia.org/wiki/Coal_gasificationhttps://en.wikipedia.org/wiki/Coal_tarhttps://en.wikipedia.org/wiki/Pyridine#cite_note-brit-7https://en.wikipedia.org/wiki/Nicotinehttps://en.wikipedia.org/wiki/Isoniazidhttps://en.wikipedia.org/wiki/Tuberculosis_treatmenthttps://en.wikipedia.org/wiki/Pyridoxalhttps://en.wikipedia.org/wiki/Niacinhttps://en.wikipedia.org/wiki/B_vitaminshttps://en.wikipedia.org/wiki/Herbicidehttps://en.wikipedia.org/wiki/Bactericidehttps://en.wikipedia.org/wiki/Mepyraminehttps://en.wikipedia.org/wiki/Tripelennaminehttps://en.wikipedia.org/wiki/Histamine_antagonisthttps://en.wikipedia.org/wiki/Sulfapyridinehttps://en.wikipedia.org/wiki/Pyridine#cite_note-Pyridine_Solution_in_DNA_Synthesis-6https://en.wikipedia.org/wiki/DNAhttps://en.wikipedia.org/wiki/Denatured_alcoholhttps://en.wikipedia.org/wiki/Ethanolhttps://en.wikipedia.org/wiki/Reagenthttps://en.wikipedia.org/wiki/Solventhttps://en.wikipedia.org/wiki/Pharmaceuticalhttps://en.wikipedia.org/wiki/Agrochemicalhttps://en.wikipedia.org/wiki/Precursor_(chemistry)https://en.wikipedia.org/wiki/Fractional_distillationhttps://en.wikipedia.org/wiki/Dippel%27s_oilhttps://en.wikipedia.org/wiki/Thomas_Anderson_(chemist)https://en.wikipedia.org/wiki/Pyridoxalhttps://en.wikipedia.org/wiki/Niacinhttps://en.wikipedia.org/wiki/Azinehttps://en.wikipedia.org/wiki/Nitrogenhttps://en.wikipedia.org/wiki/Methine_grouphttps://en.wikipedia.org/wiki/Benzenehttps://en.wikipedia.org/wiki/Nitrogenhttps://en.wikipedia.org/wiki/Hydrogenhttps://en.wikipedia.org/wiki/Carbonhttps://en.wikipedia.org/wiki/Chemical_formulahttps://en.wikipedia.org/wiki/Organic_compoundhttps://en.wikipedia.org/wiki/Heterocyclic_compoundhttps://en.wikipedia.org/wiki/Pyridine#cite_note-1https://en.wikipedia.org/wiki/Densityhttps://en.wikipedia.org/wiki/Molar_masshttps://en.wikipedia.org/wiki/Molecular_formulahttp://chemapps.stolaf.edu/jmol/jmol.php?model=c1ccncc1https://en.wikipedia.org/wiki/Jmolhttps://www.ebi.ac.uk/chembldb/index.php/compound/inspect/CHEMBL266158https://en.wikipedia.org/wiki/ChEMBLhttps://www.ebi.ac.uk/chebi/searchId.do?chebiId=16227https://en.wikipedia.org/wiki/ChEBIhttp://www.kegg.jp/entry/C00747https://en.wikipedia.org/wiki/KEGGhttp://esis.jrc.ec.europa.eu/lib/einecs_IS_reponse.php?genre=ECNO&entree=203-809-9https://en.wikipedia.org/wiki/EC_number_(chemistry)http://fdasis.nlm.nih.gov/srs/srsdirect.jsp?regno=NH9L3PP67Shttps://en.wikipedia.org/wiki/Unique_Ingredient_Identifierhttp://www.chemspider.com/1020https://en.wikipedia.org/wiki/ChemSpiderhttp://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=1049https://en.wikipedia.org/wiki/PubChemhttp://www.commonchemistry.org/ChemicalDetail.aspx?ref=110-86-1https://en.wikipedia.org/wiki/CAS_registry_numberhttps://en.wikipedia.org/wiki/File:Pyridine_sample.jpghttps://en.wikipedia.org/wiki/File:Pyridine-CRC-MW-3D-vdW.pnghttps://en.wikipedia.org/wiki/File:Pyridine-CRC-MW-3D-balls.pnghttps://en.wikipedia.org/wiki/File:Pyridine_numbers.svghttps://en.wikipedia.org/wiki/File:Pyridine-2D-full.svg


2/15



Melting point41.6 C, 232 K, -43 F

Boiling point115.2 C, 388 K, 239 F

Solubility in water Miscible

Vapor pressure 18 mmHg

Acidity (pKa) 5.25 (for the conjugate acid)[2][3]

Refractive index (nD) 1.5093Viscosity 0.88 cP

Dipole moment 2.2 D[4]

Hazards[5]

MSDS External MSDS

EU classification Flammable (F)

Harmful (Xn)

R-phrases R20 R21 R22 R34 R36 R38

NFPA 704

Flash point 21 C

Threshold Limit Value 5 ppm (TWA)

Related compounds

Related amines Picoline

Quinoline

Related compounds Aniline

Pyrimidine

Piperidine

Supplementary data pageStructure and

properties

n, r, etc.

Thermodynamic

data

Phase behaviour

Solid, liquid, gas

Spectral data UV, IR, NMR, MS

(verify) (what is: / ?)

Except where noted otherwise, data are given for materials in

their standard state (at 25 C, 100 kPa)

Infobox references

Crystal structure of pyridine

Properties

Physical properties

Pyridine is a colorless liquid that boils at 115.2 C and freezes at41.6 C. Its density, 0.9819 g/cm3, is close to that of water, and itsrefractive index is 1.5093 at a wavelength of 589 nm and a temperature

of 20 C.[8] Addition of up to 40 mol% of water to pyridine graduallylowers its melting point from 41.6 C to 65.0 C.[9] The molecularelectric dipole moment is 2.2 Debye.[4] Pyridine is diamagnetic and has adiamagnetic susceptibility of 48.7 106 cm3mol1.[10] The standardenthalpy of formation is 100.2 kJmol1 in the liquid phase[11] and 140.4kJmol1 in the gas phase. At 25 C pyridine has a viscosity[12] of 0.88mPa/s and thermal conductivity of 0.166 Wm1K1.[13][14] Theenthalpy of vaporization is 35.09 kJmol1 at the boiling point and normal

pressure.[15] The enthalpy of fusion is 8.28 kJmol1 at the meltingpoint.[16]

Pyridine crystallizes in an orthorhombic crystal system with space groupPna21 and lattice parameters a = 1752, b = 897, c = 1135 pm, and 16formula units per unit cell (measured at 153 K). For comparison, benzenecrystal is also orthorhombic, with space groupPbca, a = 729.2 pm, b =947.1 pm, c = 674.2 pm (at 78 K), but the number of molecules per cellis only 4.[17] This difference is partly related to the lower symmetry of theindividual pyridine molecule (C2v vs. D6h for benzene). A trihydrate(pyridine3H2O) is known; it also crystallizes in an orthorhombic systemin the space groupPbca, lattice parameters a = 1244, b = 1783, c =679 pm and eight formula units per unit cell (measured at 223 K). [9]

The critical parameters of pyridine are pressure 6.70 MPa, temperature

620 K and volume 229 cm3mol1.[18] In the temperature range 340426 C its vapor pressurep can be described with the Antoine equation

where Tis temperature,A = 4.16272,B = 1371.358 K and C=-58.496 K.[19]

The optical absorption spectrum of pyridine in hexane contains threebands at the wavelengths of 195 nm ( *transition, molarabsorptivity = 7500 L(molcm)1), 251 nm ( *transition,

= 2000 L(molcm)1) and 270 nm (n *transition, = 450 L(molcm)1).[20] The 1Hnuclear magnetic resonance (NMR) spectrum of pyridine contains three signals with the integralintensity ratio of 2:1:2 which correspond to the three chemically different protons in the molecule.These signals originate from the -protons (chemical shift 8.5 ppm), -proton (7.5 ppm) and -

protons (7.1 ppm). The carbon analog of pyridine, benzene, has only one proton signal at 7.27ppm. The larger chemical shifts of the - and -protons in comparison to benzene result from thelower electron density in the - and -positions, which can be derived from the resonancestructures. The situation is rather similar for the 13C NMR spectra of pyridine and benzene:

pyridine shows a triplet at (-C) = 150 ppm, (-C) = 124 ppm and (-C) = 136 ppm,whereas benzene has a single line at 129 ppm. All shifts are quoted for the solvent-freesubstances.[21] Pyridine is conventionally detected by the gas chromatography and Massspectrometry methods.[22]

Chemical properties

33 0
https://en.wikipedia.org/wiki/Pyridine#cite_note-lide3448-8https://en.wikipedia.org/wiki/File:NFPA_704.svghttps://en.wikipedia.org/wiki/Pyridine#cite_note-lide3448-8https://en.wikipedia.org/wiki/Pyridine#cite_note-osha-22https://en.wikipedia.org/wiki/Mass_spectrometryhttps://en.wikipedia.org/wiki/Gas_chromatographyhttps://en.wikipedia.org/wiki/Pyridine#cite_note-21https://en.wikipedia.org/wiki/Chemical_shifthttps://en.wikipedia.org/wiki/Nuclear_magnetic_resonancehttps://en.wikipedia.org/wiki/Pyridine#cite_note-20https://en.wikipedia.org/wiki/Molar_absorptivityhttps://en.wikipedia.org/wiki/Wavelengthhttps://en.wikipedia.org/wiki/Hexanehttps://en.wikipedia.org/wiki/Pyridine#cite_note-19https://en.wikipedia.org/wiki/Antoine_equationhttps://en.wikipedia.org/wiki/Pyridine#cite_note-18https://en.wikipedia.org/wiki/Critical_point_(thermodynamics)https://en.wikipedia.org/wiki/Pyridine#cite_note-str-9https://en.wikipedia.org/wiki/Hydratehttps://en.wikipedia.org/wiki/Pyridine#cite_note-17https://en.wikipedia.org/wiki/Unit_cellhttps://en.wikipedia.org/wiki/Formula_unithttps://en.wikipedia.org/wiki/Picometerhttps://en.wikipedia.org/wiki/Space_grouphttps://en.wikipedia.org/wiki/Orthorhombic_crystal_systemhttps://en.wikipedia.org/wiki/Pyridine#cite_note-16https://en.wikipedia.org/wiki/Melting_pointhttps://en.wikipedia.org/wiki/Enthalpy_of_fusionhttps://en.wikipedia.org/wiki/Pyridine#cite_note-Majer_Svoboda-15https://en.wikipedia.org/wiki/Boiling_pointhttps://en.wikipedia.org/wiki/Enthalpy_of_vaporizationhttps://en.wikipedia.org/wiki/Pyridine#cite_note-GESTIS-14https://en.wikipedia.org/wiki/Pyridine#cite_note-13https://en.wikipedia.org/wiki/Thermal_conductivityhttps://en.wikipedia.org/wiki/Pyridine#cite_note-12https://en.wikipedia.org/wiki/Viscosityhttps://en.wikipedia.org/wiki/Pyridine#cite_note-lide528-11https://en.wikipedia.org/wiki/Standard_enthalpy_of_formationhttps://en.wikipedia.org/wiki/Pyridine#cite_note-10https://en.wikipedia.org/wiki/Magnetic_susceptibilityhttps://en.wikipedia.org/wiki/Diamagnetismhttps://en.wikipedia.org/wiki/Pyridine#cite_note-roempp-4https://en.wikipedia.org/wiki/Debyehttps://en.wikipedia.org/wiki/Electric_dipole_momenthttps://en.wikipedia.org/wiki/Pyridine#cite_note-str-9https://en.wikipedia.org/wiki/Pyridine#cite_note-lide3448-8https://en.wikipedia.org/wiki/Wavelengthhttps://en.wikipedia.org/wiki/Refractive_indexhttps://en.wikipedia.org/wiki/File:Kristallstruktur_Pyridin.pnghttps://en.wikipedia.org/wiki/Wikipedia:Chemical_infobox#Referenceshttps://en.wikipedia.org/wiki/Standard_statehttps://en.wikipedia.org/wiki/Wikipedia:WikiProject_Chemicals/Chembox_validationhttps://en.wikipedia.org/w/index.php?title=Special:ComparePages&rev1=414415928&page2=Pyridinehttps://en.wikipedia.org/wiki/Mass_spectrometryhttps://en.wikipedia.org/wiki/NMR_spectroscopyhttps://en.wikipedia.org/wiki/Infrared_spectroscopyhttps://en.wikipedia.org/wiki/UV/VIS_spectroscopyhttps://en.wikipedia.org/wiki/Pyridine_(data_page)#Spectral_datahttps://en.wikipedia.org/wiki/Pyridine_(data_page)#Thermodynamic_propertieshttps://en.wikipedia.org/wiki/Dielectric_constanthttps://en.wikipedia.org/wiki/Refractive_indexhttps://en.wikipedia.org/wiki/Pyridine_(data_page)#Structure_and_propertieshttps://en.wikipedia.org/wiki/Pyridine_(data_page)https://en.wikipedia.org/wiki/Piperidinehttps://en.wikipedia.org/wiki/Pyrimidinehttps://en.wikipedia.org/wiki/Anilinehttps://en.wikipedia.org/wiki/Quinolinehttps://en.wikipedia.org/wiki/Picolinehttps://en.wikipedia.org/wiki/Aminehttps://en.wikipedia.org/wiki/Threshold_Limit_Valuehttps://en.wikipedia.org/wiki/Flash_pointhttps://en.wikipedia.org/wiki/NFPA_704https://en.wikipedia.org/wiki/R38:_Irritating_to_skinhttps://en.wikipedia.org/wiki/R36:_Irritating_to_eyeshttps://en.wikipedia.org/wiki/R34:_Causes_burnshttps://en.wikipedia.org/wiki/R22:_Harmful_if_swallowedhttps://en.wikipedia.org/wiki/R21:_Harmful_in_contact_with_skinhttps://en.wikipedia.org/wiki/R20:_Harmful_by_inhalationhttps://en.wikipedia.org/wiki/List_of_R-phraseshttps://en.wikipedia.org/wiki/Dangerous_Substances_Directive_(67/548/EEC)https://en.wikipedia.org/wiki/Pyridine_(data_page)#Material_Safety_Data_Sheethttps://en.wikipedia.org/wiki/Material_safety_data_sheethttps://en.wikipedia.org/wiki/Pyridine#cite_note-5https://en.wikipedia.org/wiki/Pyridine#cite_note-roempp-4https://en.wikipedia.org/wiki/Dipole#Molecular_dipoleshttps://en.wikipedia.org/wiki/Poisehttps://en.wikipedia.org/wiki/Viscosityhttps://en.wikipedia.org/wiki/Refractive_indexhttps://en.wikipedia.org/wiki/Pyridine#cite_note-3https://en.wikipedia.org/wiki/Pyridine#cite_note-2https://en.wikipedia.org/wiki/Acid_dissociation_constanthttps://en.wikipedia.org/wiki/Vapor_pressurehttps://en.wikipedia.org/wiki/Waterhttps://en.wikipedia.org/wiki/Solubilityhttps://en.wikipedia.org/wiki/Boiling_pointhttps://en.wikipedia.org/wiki/Melting_point


3/15



1,10-phenanthroline

Pyridine with its

free electron

pair

Pyridine is miscible with water and virtually all organic solvents.[8] It is weakly basic, and with hydrochloric acid it forms a crystallinehydrochloride salt which melts at 145147 C.[23] Most chemical properties of pyridine are typical of a heteroaromatic compound. Inorganic reactions, pyridine behaves both as a tertiary amine, undergoing protonation, alkylation, acylation, and N-oxidation at the nitrogenatom, and as an aromatic compound, undergoing nucleophilic substitutions.

Because of the electronegative nitrogen in the pyridine ring, the molecule is relatively electron deficient. It therefore enters less readilyelectrophilic aromatic substitution reactions, which are characteristic of benzene derivatives. However, unlike benzene and its derivatives,

pyridine is more prone to nucleophilic substitution and metalation of the ring by strong organometallic bases.[24][25] The reactivity ofpyridine can be distinguished for three chemical groups. With electrophiles, electrophilic substitution takes place where pyridine expresses

aromatic properties. With nucleophiles, pyridine reacts via its 2nd and 4th carbon atoms and thus behaves similar to imines and carbonyls.The reaction with many Lewis acids results in the addition to the nitrogen atom of pyridine, which is similar to the reactivity of tertiaryamines. The ability of pyridine and its derivatives to oxidize, forming amine oxides (N-oxides), is also a feature of tertiary amines.[26]

The nitrogen center of pyridine features a basic lone pair of electrons. Because this lone pair is not part of thearomatic ring, pyridine is a base, having chemical properties similar to those of tertiary amines. The pKa of theconjugate acid is 5.25. Pyridine is protonated by reaction with acids and forms a positively charged aromatic

polyatomic ion called pyridinium. The bond lengths and bond angles in pyridine and pyridinium are almostidentical.[27] The pyridinium cation is isoelectronic with benzene. Pyridiniump-toluenesulfonate (PPTS) is anillustrative pyridinium salt; it is produced by treating pyridine withp-toluenesulfonic acid.

Pyridine can act as Lewis base, donating its pair of electron to a Lewis acid as in the sulfur trioxide pyridine complex.

Pyridine itself is a relatively weak ligand in forming complexes with transition metal ions. For example, it forms a 1:1 complexes withnickel(II), Ni2+, and copper(II), Cu2+, with logK1 values of ca. 1.9 and 2.6, respectively.

[28] The infrared spectra of pyridine complexes

have been discussed in detail.[29][30] Picolinic acid, which is a substituted derivative of pyridine, forms strong complexes due to the chelateeffect; 2,2'-bipyridine and 1,10-phenanthroline, which can also be viewed as substituted derivatives of pyridine, also form strongcomplexes, such as in Ferroin which can be used as an redox indicator in the quantitative analysis of iron.[31]

The 6 coordination mode, as occurs in 6 benzene complexes, is only observed in sterically encumbered derivatives that block thenitrogen center.[32]

Molecular properties

Pyridine has a conjugated system of six -electrons that are delocalized over the ring. The molecule is planar and thusfollows the Hckel criteria for aromatic systems. In contrast to benzene, the electron density is not evenly distributedover the ring, reflecting the negative inductive effect of the nitrogen atom. For this reason, pyridine has a dipolemoment and a weaker resonant stabilization than benzene (resonance energy 117 kJmol1 in pyridine vs. 150kJmol1 in benzene).[33] The electron localization in pyridine is also reflected in the shorter CN ring bond (137 pmfor the CN bond in pyridine vs. 139 pm for CC bond in benzene), [34] whereas the carboncarbon bonds in the

pyridine ring have the same 139 pm length as in benzene. These bond lengths lie between the values for the single anddouble bonds and are typical of aromatic compounds.

All the ring atoms in the pyridine molecule are sp2-hybridized. The nitrogen atom "donates" its three hybridizedelectrons to the ring system, and its extra electron pair lies in the molecule plane, projecting outwards, in the plane ofthe ring. This lone pair does not contribute to the aromatic system but importantly influences the chemical properties of pyridine, as it easily

supports bond formation via an electrophilic attack. However, because of the separation of the lone pair from the aromatic system of thering affects, the nitrogen atom can not exhibit a positive mesomeric effect.

Many analogues of pyridine are known where N is replaced by other heteroatoms (see Figure). Substitution of one CH in pyridine with asecond N gives rise to the "diaza" heterocycles (C4H4N2), with the names pyridazine, pyrimidine, and pyrazine.
https://en.wikipedia.org/wiki/Pyrazinehttps://en.wikipedia.org/wiki/Pyrimidinehttps://en.wikipedia.org/wiki/Pyridazinehttps://en.wikipedia.org/wiki/Mesomeric_effecthttps://en.wikipedia.org/wiki/Lone_pairhttps://en.wikipedia.org/wiki/Orbital_hybridisation#sp2_hybridshttps://en.wikipedia.org/wiki/Double_bondhttps://en.wikipedia.org/wiki/Pyridine#cite_note-34https://en.wikipedia.org/wiki/Picometerhttps://en.wikipedia.org/wiki/Pyridine#cite_note-33https://en.wikipedia.org/wiki/Resonance_(chemistry)#Resonance_energyhttps://en.wikipedia.org/wiki/Resonance_(chemistry)https://en.wikipedia.org/wiki/Inductive_effecthttps://en.wikipedia.org/wiki/Electron_densityhttps://en.wikipedia.org/wiki/H%C3%BCckel_rulehttps://en.wikipedia.org/wiki/Pi_bondhttps://en.wikipedia.org/wiki/Conjugation_(organic_chemistry)https://en.wikipedia.org/wiki/Pyridine#cite_note-32https://en.wikipedia.org/wiki/Steric_effectshttps://en.wikipedia.org/wiki/Pyridine#cite_note-31https://en.wikipedia.org/wiki/Quantitative_analysis_(chemistry)https://en.wikipedia.org/wiki/Redox_indicatorhttps://en.wikipedia.org/wiki/Ferroinhttps://en.wikipedia.org/wiki/Chelate_effecthttps://en.wikipedia.org/wiki/Pyridine#cite_note-30https://en.wikipedia.org/wiki/Pyridine#cite_note-nakamoto-29https://en.wikipedia.org/wiki/Infrared_spectrumhttps://en.wikipedia.org/wiki/Pyridine#cite_note-scdb-28https://en.wikipedia.org/wiki/Transition_metalhttps://en.wikipedia.org/wiki/Coordination_complexhttps://en.wikipedia.org/wiki/Sulfur_trioxide_pyridine_complexhttps://en.wikipedia.org/wiki/Lewis_basehttps://en.wikipedia.org/wiki/P-Toluenesulfonic_acidhttps://en.wikipedia.org/wiki/Toluenesulfonic_acidhttps://en.wikipedia.org/wiki/Isoelectronichttps://en.wikipedia.org/wiki/Pyridine#cite_note-27https://en.wikipedia.org/wiki/Bond_anglehttps://en.wikipedia.org/wiki/Bond_lengthhttps://en.wikipedia.org/wiki/Pyridiniumhttps://en.wikipedia.org/wiki/Polyatomic_ionhttps://en.wikipedia.org/wiki/Acidhttps://en.wikipedia.org/wiki/Chemical_reactionhttps://en.wikipedia.org/wiki/Protonationhttps://en.wikipedia.org/wiki/Conjugate_acidhttps://en.wikipedia.org/wiki/PKahttps://en.wikipedia.org/wiki/Tertiary_aminehttps://en.wikipedia.org/wiki/Base_(chemistry)https://en.wikipedia.org/wiki/Electronhttps://en.wikipedia.org/wiki/Lone_pairhttps://en.wikipedia.org/wiki/Pyridine#cite_note-26https://en.wikipedia.org/wiki/Amine_oxidehttps://en.wikipedia.org/wiki/Lewis_acidhttps://en.wikipedia.org/wiki/Carbonylhttps://en.wikipedia.org/wiki/Iminehttps://en.wikipedia.org/wiki/Nucleophilehttps://en.wikipedia.org/wiki/Electrophilic_substitutionhttps://en.wikipedia.org/wiki/Electrophilehttps://en.wikipedia.org/wiki/Pyridine#cite_note-davies-25https://en.wikipedia.org/wiki/Pyridine#cite_note-jou10-24https://en.wikipedia.org/wiki/Metalationhttps://en.wikipedia.org/wiki/Nucleophilic_substitutionhttps://en.wikipedia.org/wiki/Electrophilic_aromatic_substitutionhttps://en.wikipedia.org/wiki/Nitrogenhttps://en.wikipedia.org/wiki/Nucleophilic_substitutionhttps://en.wikipedia.org/wiki/Aromatic_compoundhttps://en.wikipedia.org/wiki/N-oxidationhttps://en.wikipedia.org/wiki/Acylationhttps://en.wikipedia.org/wiki/Alkylationhttps://en.wikipedia.org/wiki/Protonationhttps://en.wikipedia.org/wiki/Aminehttps://en.wikipedia.org/wiki/Organic_reactionhttps://en.wikipedia.org/wiki/Heteroaromatichttps://en.wikipedia.org/wiki/Pyridine#cite_note-23https://en.wikipedia.org/wiki/Hydrochloridehttps://en.wikipedia.org/wiki/Hydrochloric_acidhttps://en.wikipedia.org/wiki/Pyridine#cite_note-lide3448-8https://en.wikipedia.org/wiki/File:Pyridine-2D-Skeletal.pnghttps://en.wikipedia.org/wiki/Phenanthrolinehttps://en.wikipedia.org/wiki/File:1,10-phenanthroline.svg


4/15



Thomas Anderson

Bond lengths and angles of benzene, pyridine, phosphorine, arsabenzene, stilbabenzene, and bismabenzene Electron orbitals in pyridine

Resonance structures of pyridine Electron orbitals in protonated

pyridine

HistoryImpure pyridine was undoubtedly prepared by early alchemists by heating animal bones and otherorganic matter,[35] but the earliest documented reference is attributed to the Scottish scientist ThomasAnderson.[36][37] In 1849, Anderson examined the contents of the oil obtained through high-temperatureheating of animal bones.[37] Among other substances, he separated from the oil a colorless liquid withunpleasant odor, from which he isolated pure pyridine two years later. He described it as highly soluble inwater, readily soluble in concentrated acids and salts upon heating, and only slightly soluble in oils. Owingto its flammability, Anderson named the new substancepyridine, after Greek: () (pyr) meaning

fire. The suffix -idine was added in compliance with the chemical nomenclature, as in toluidine, toindicate a carbon cycle containing a nitrogen atom.[38]
https://en.wikipedia.org/wiki/Pyridine#cite_note-40https://en.wikipedia.org/wiki/Pyridine#cite_note-39https://en.wikipedia.org/wiki/Pyridine#cite_note-anderson2-38https://en.wikipedia.org/wiki/Toluidinehttps://en.wikipedia.org/wiki/Greek_languagehttps://en.wikipedia.org/wiki/Pyridine#cite_note-ReferenceA-37https://en.wikipedia.org/wiki/Pyridine#cite_note-ReferenceA-37https://en.wikipedia.org/wiki/Pyridine#cite_note-36https://en.wikipedia.org/wiki/Thomas_Anderson_(chemist)https://en.wikipedia.org/wiki/Pyridine#cite_note-weiss-35https://en.wikipedia.org/wiki/File:Pyridinium-orbitals.svghttps://en.wikipedia.org/wiki/File:Pyridine-10.pnghttps://en.wikipedia.org/wiki/File:Pyridine-orbitals.svghttps://en.wikipedia.org/wiki/Arsabenzenehttps://en.wikipedia.org/wiki/Phosphorinehttps://en.wikipedia.org/wiki/File:Bond_lengths_of_group_15_heterobenzenes_and_benzene.svghttps://en.wikipedia.org/wiki/File:ThomasAnderson(1819-1874).jpg


5/15



The chemical structure of pyridine was determined decades after its discovery. Wilhelm Krner (1869)[39] and James Dewar (1871)[40]

independently suggested that, in analogy between quinoline and naphthalene, the structure of pyridine is derived from benzene bysubstituting one CH unit with a nitrogen atom.[41][42] The suggestion by Krner and Dewar was later confirmed in an experiment where

pyridine was reduced to piperidine with sodium in ethanol. In 1876, William Ramsay combined acetylene and hydrogen cyanide intopyridine in a red-hot iron-tube furnace. This was the first synthesis of a hetero-aromatic compound.[22][43]

The contemporary methods of pyridine production had a low yield, and the increasing demand for the new compound urged to search formore efficient routes. A breakthrough came in 1924 when the Russian chemist Aleksei Chichibabin invented a pyridine synthesis reactionwhich was based on inexpensive reagents.[44] This method is still used for the industrial production of pyridine.[45]

Occurrence

Pyridine is not abundant in nature, except for the leaves and roots of belladonna (Atropa belladonna)[46] and in marshmallow (Althaeaofficinalis).[47] Pyridine derivatives, however, are often part of biomolecules such as the eponymous pyridine nucleotides and alkaloids.

In daily life, trace amounts of pyridine are components of the volatile organic compounds that are produced in roasting and canningprocesses, e.g. in fried chicken,[48] sukiyaki,[49] roasted coffee,[50] potato chips,[51] and fried bacon.[52] Traces of pyridine can be found inBeaufort cheese,[53] vaginal secretions,[54] black tea,[55] saliva of those suffering from gingivitis,[56] and sunflower honey.[57] The smoke of

tobacco

[58][59]

and marijuana

[22]

also contain small amounts of pyridine.

Nomenclature

The systematic name of pyridine, within the HantzschWidman nomenclature recommended by the IUPAC, is azine. However, systematicnames for simple compounds are used very rarely, instead heterocyclic nomenclature follows historically established common names.IUPAC discourages the use ofazine in favor ofpyridine.[60] The numbering of the ring atoms in pyridine starts at the nitrogen (seeinfobox). An allocation of positions by letter of the Greek alphabet (-) and the substitution pattern nomenclature common forhomoaromatic systems (ortho, meta,para) are used sometimes. Here (ortho), (meta) and (para) refer to the 2, 3 and 4 position,respectively. The systematic name for the pyridine derivatives ispyridinyl, wherein the position of the substituted atom is preceded by anumber. However, here again the historical namepyridylis encouraged by the IUPAC and used instead of the systematic name.[61] Thecationic derivative formed by the addition of an electrophile to the nitrogen atom is called pyridinium.

4-bromopyridine

2,2-bipyridine

pyridine-2,6-dicarboxylicacid (dipicolinic acid)

General form of thepyridinium cation

Production

Historically, pyridine was extracted from coal tar or obtained as a by-product of coal gasification. The process was labor consuming andinefficient: coal tar contains only about 0.1% pyridine,[62] and therefore a multi-stage purification was required, which further reduced theoutput. Nowadays, most pyridine is produced synthetically using various name reactions, and the major ones are discussed below. [45]

Chichibabin synthesis

The Chichibabin pyridine synthesis was reported in 1924 and is still in use industrially.[44] In its general form, the reaction can be described

as a condensation reaction of aldehydes, ketones, ,-Unsaturated carbonyl compounds, or any combination of the above, in ammonia orammonia derivatives.[63] In particular, unsubstituted pyridine is produced from formaldehyde and acetaldehyde, which are inexpensive andwidely available. First, acrolein is formed in a Knoevenagel condensation from the acetaldehyde and formaldehyde. It is then condensedwith acetaldehyde and ammonia into dihydropyridine, and then oxidized with a solid-state catalyst to pyridine. This process is carried out ina gas phase at 400450 C. The product consists of a mixture of pyridine, simple methylated pyridines (picoline) and lutidine; its
https://en.wikipedia.org/wiki/Lutidinehttps://en.wikipedia.org/wiki/Picolinehttps://en.wikipedia.org/wiki/Methyl_grouphttps://en.wikipedia.org/wiki/Dihydropyridinehttps://en.wikipedia.org/wiki/Condensation_reactionhttps://en.wikipedia.org/wiki/Knoevenagel_condensationhttps://en.wikipedia.org/wiki/Acroleinhttps://en.wikipedia.org/wiki/Acetaldehydehttps://en.wikipedia.org/wiki/Formaldehydehttps://en.wikipedia.org/wiki/Pyridine#cite_note-Frank1949-63https://en.wikipedia.org/wiki/Aminehttps://en.wikipedia.org/wiki/Ammoniahttps://en.wikipedia.org/wiki/%CE%91,%CE%B2-Unsaturated_carbonyl_compoundhttps://en.wikipedia.org/wiki/Ketoneshttps://en.wikipedia.org/wiki/Aldehydeshttps://en.wikipedia.org/wiki/Condensation_reactionhttps://en.wikipedia.org/wiki/Pyridine#cite_note-tschi-44https://en.wikipedia.org/wiki/Chichibabin_pyridine_synthesishttps://en.wikipedia.org/wiki/Pyridine#cite_note-ul-45https://en.wikipedia.org/wiki/Name_reactionhttps://en.wikipedia.org/wiki/Pyridine#cite_note-62https://en.wikipedia.org/wiki/Coal_tarhttps://en.wikipedia.org/wiki/Pyridiniumhttps://en.wikipedia.org/wiki/Electrophilehttps://en.wikipedia.org/wiki/Cationhttps://en.wikipedia.org/wiki/Pyridine#cite_note-61https://en.wikipedia.org/wiki/Arene_substitution_patternshttps://en.wikipedia.org/wiki/Greek_alphabethttps://en.wikipedia.org/wiki/Pyridine#cite_note-60https://en.wikipedia.org/wiki/IUPAChttps://en.wikipedia.org/wiki/Hantzsch%E2%80%93Widman_nomenclaturehttps://en.wikipedia.org/wiki/Pyridine#cite_note-osha-22https://en.wikipedia.org/wiki/Marijuanahttps://en.wikipedia.org/wiki/Pyridine#cite_note-59https://en.wikipedia.org/wiki/Pyridine#cite_note-58https://en.wikipedia.org/wiki/Pyridine#cite_note-57https://en.wikipedia.org/wiki/Monofloral_honeyhttps://en.wikipedia.org/wiki/Pyridine#cite_note-56https://en.wikipedia.org/wiki/Gingivitishttps://en.wikipedia.org/wiki/Pyridine#cite_note-55https://en.wikipedia.org/wiki/Black_teahttps://en.wikipedia.org/wiki/Pyridine#cite_note-54https://en.wikipedia.org/wiki/Vaginal_lubricationhttps://en.wikipedia.org/wiki/Pyridine#cite_note-53https://en.wikipedia.org/wiki/Beaufort_(cheese)https://en.wikipedia.org/wiki/Pyridine#cite_note-52https://en.wikipedia.org/wiki/Baconhttps://en.wikipedia.org/wiki/Pyridine#cite_note-51https://en.wikipedia.org/wiki/Pyridine#cite_note-50https://en.wikipedia.org/wiki/Pyridine#cite_note-49https://en.wikipedia.org/wiki/Sukiyakihttps://en.wikipedia.org/wiki/Pyridine#cite_note-48https://en.wikipedia.org/wiki/Canninghttps://en.wikipedia.org/wiki/Volatile_organic_compoundhttps://en.wikipedia.org/wiki/Pyridine#cite_note-47https://en.wikipedia.org/wiki/Althaea_officinalishttps://en.wikipedia.org/wiki/Pyridine#cite_note-46https://en.wikipedia.org/wiki/Atropa_belladonnahttps://en.wikipedia.org/wiki/Pyridine#cite_note-ul-45https://en.wikipedia.org/wiki/Pyridine#cite_note-tschi-44https://en.wikipedia.org/wiki/Chichibabin_pyridine_synthesishttps://en.wikipedia.org/wiki/Aleksei_Chichibabinhttps://en.wikipedia.org/wiki/Pyridine#cite_note-43https://en.wikipedia.org/wiki/Pyridine#cite_note-osha-22https://en.wikipedia.org/wiki/Red_heathttps://en.wikipedia.org/wiki/Hydrogen_cyanidehttps://en.wikipedia.org/wiki/Acetylenehttps://en.wikipedia.org/wiki/William_Ramsayhttps://en.wikipedia.org/wiki/Sodiumhttps://en.wikipedia.org/wiki/Piperidinehttps://en.wikipedia.org/wiki/Pyridine#cite_note-42https://en.wikipedia.org/wiki/Pyridine#cite_note-41https://en.wikipedia.org/wiki/Benzenehttps://en.wikipedia.org/wiki/Naphthalenehttps://en.wikipedia.org/wiki/Quinolinehttps://en.wikipedia.org/wiki/Pyridine#cite_note-40https://en.wikipedia.org/wiki/James_Dewarhttps://en.wikipedia.org/wiki/Pyridine#cite_note-39https://en.wikipedia.org/wiki/Wilhelm_K%C3%B6rnerhttps://en.wikipedia.org/wiki/Pyridiniumhttps://en.wikipedia.org/wiki/Dipicolinic_acid


6/15



Bnnemann cyclization

composition depends on the catalyst used and can be adapted to the needs of the manufacturer. The catalyst is usually a transition metalsalt such as cadmium(II) fluoride or manganese(II) fluoride, but cobalt and thallium compounds can also be used. The recovered pyridine isseparated from by-products in a multistage process.[45]

Formation of acrolein from acetaldehyde and formaldehyde

Condensation of pyridine from acrolein and acetaldehyde

Practical application of the traditional Chichibabin pyridine synthesis are limited by its consistently low yield, typically about 20%. This lowyield, together with the high prevalence of byproducts, render unmodified forms of Chichibabin's method unpopular. [63]

Dealkylation of alkylpyridines

Pyridine can be prepared by dealkylation of alkylated pyridines, which are obtained as by-products in the syntheses of other pyridines. Theoxidative dealkylation is carried out either using air over vanadium(V) oxide catalyst, [64] by vapor-dealkylation on nickel-basedcatalyst,[65][66] or hydrodealkylation with a silver or platinum based catalyst.[67] Yields of pyridine up to be 93% can be achieved with thenickel-based catalyst.[45]

Hantzsch pyridine synthesis

The first major synthesis of pyridine derivatives was described in 1881 by Arthur Rudolf Hantzsch.[68] The Hantzsch pyridine synthesistypically uses a 2:1:1 mixture of a -keto acid (often acetoacetate), an aldehyde (often formaldehyde), and ammonia or its salt as thenitrogen donor. First, a double hydrogenated pyridine is obtained, which is then oxidized to the corresponding pyridine derivative. Emil

Knoevenagel showed that unsymmetrically substituted pyridine derivatives can be produced with this process.[69]

Hantzsch pyridine synthesis with acetoacetate, formaldehyde and ammonium acetate, and iron(III) chloride as the catalyst.

Bnnemann cyclization

The trimerization of a part of a nitrile molecule and two parts of acetylene into pyridine is calledBnnemann cyclization. This modification of the Reppe synthesis can be activated either byheat or light. While the thermal activation requires high pressures and temperatures, the

photoinduced cycloaddition proceeds at ambient conditions with CoCp2(cod) (Cp =cyclopentadienyl, cod = 1,5-cyclooctadiene) as a catalyst, and can be performed even inwater.[70] A series of pyridine derivatives can be produced in this way. When using acetonitrileas the nitrile, 2-methylpyridine is obtained, which can be dealkylated to pyridine.

Other methods

The Krhnke pyridine synthesis involves the condensation of 1,5-diketones with ammonium acetate in acetic acid followed byoxidation.[71]
https://en.wikipedia.org/wiki/Pyridine#cite_note-71https://en.wikipedia.org/wiki/Acetic_acidhttps://en.wikipedia.org/wiki/Ammonium_acetatehttps://en.wikipedia.org/wiki/Ketonehttps://en.wikipedia.org/wiki/Acetonitrilehttps://en.wikipedia.org/wiki/Pyridine#cite_note-70https://en.wikipedia.org/wiki/1,5-cyclooctadienehttps://en.wikipedia.org/wiki/Cycloadditionhttps://en.wikipedia.org/wiki/Photochemistryhttps://en.wikipedia.org/wiki/Walter_Reppehttps://en.wikipedia.org/wiki/Acetylenehttps://en.wikipedia.org/wiki/Nitrilehttps://en.wikipedia.org/wiki/Iron(III)_chloridehttps://en.wikipedia.org/wiki/Ammonium_acetatehttps://en.wikipedia.org/wiki/Hantzsch_pyridine_synthesishttps://en.wikipedia.org/wiki/File:Hantzsch_pyridine_synthesis.svghttps://en.wikipedia.org/wiki/Pyridine#cite_note-69https://en.wikipedia.org/wiki/Emil_Knoevenagelhttps://en.wikipedia.org/wiki/Hydration_reactionhttps://en.wikipedia.org/wiki/Ammoniahttps://en.wikipedia.org/wiki/Formaldehydehttps://en.wikipedia.org/wiki/Aldehydehttps://en.wikipedia.org/wiki/Acetoacetic_acidhttps://en.wikipedia.org/wiki/Keto_acidhttps://en.wikipedia.org/wiki/Hantzsch_pyridine_synthesishttps://en.wikipedia.org/wiki/Pyridine#cite_note-68https://en.wikipedia.org/wiki/Arthur_Rudolf_Hantzschhttps://en.wikipedia.org/wiki/Pyridine#cite_note-ul-45https://en.wikipedia.org/wiki/Pyridine#cite_note-67https://en.wikipedia.org/wiki/Platinumhttps://en.wikipedia.org/wiki/Pyridine#cite_note-66https://en.wikipedia.org/wiki/Pyridine#cite_note-65https://en.wikipedia.org/wiki/Pyridine#cite_note-64https://en.wikipedia.org/wiki/Vanadium(V)_oxidehttps://en.wikipedia.org/wiki/Pyridine#cite_note-Frank1949-63https://en.wikipedia.org/wiki/File:Pyridin_aus_Acrolein.svghttps://en.wikipedia.org/wiki/File:AcroleinDarstellung.svghttps://en.wikipedia.org/wiki/Pyridine#cite_note-ul-45https://en.wikipedia.org/wiki/Thalliumhttps://en.wikipedia.org/wiki/Cobalthttps://en.wikipedia.org/wiki/Manganese(II)_fluoridehttps://en.wikipedia.org/wiki/Cadmium(II)_fluoridehttps://en.wikipedia.org/wiki/File:B%C3%B6nnemannEn.png


7/15



The Ciamician-Dennstedt rearrangement entails the ring-expansion of pyrrole with dichlorocarbene to 3-chloropyridine.[72][73][74][75]

In the Gattermann-Skita synthes is,[76] a malonate ester salt reacts with dichloromethylamine.[77]

Biosynthesis

Several pyridine derivatives play important roles in biological systems. While its biosynthesis is not fully understood, nicotinic acid (vitaminB3) occurs in some bacteria, fungi and mammals. Mammals synthesize nicotinic acid through oxidation of the amino acid tryptophan, wherean intermediate product, aniline, creates a pyridine derivative, kynurenine. On the contrary, the bacteriaMycobacterium tuberculosis and

Escherichia coli produce nicotinic acid by condensation of glyceraldehyde 3-phosphate and aspartic acid.[78]

Reactions

Many reactions that are characteristic of benzene proceed with pyridine either at more complicated conditions or/and with low yield.

Owing to the decreased electron density in the aromatic system, electrophilic substitutions are suppressed in pyridine and its derivatives infavor of addition of nucleophiles at the electron-rich nitrogen atom. The nucleophilic addition at the nitrogen atom leads to a furtherdeactivation of the aromatic properties and hindering of the electrophilic substitution. On the other hand, free-radical and nucleophilicsubstitutions occur more readily in pyridine than in benzene.[4][24]

Electrophilic substitutions

Many electrophilic substitutions on pyridine either do not proceed or proceed only partially; however, the heteroaromatic character can beactivated by electron-donating functionalization. Common alkylations and acylations, such as FriedelCrafts alkylation or acylation, usuallyfail for pyridine because they only lead to the addition at the nitrogen atom. Substitutions usually occur at the 3-position which is the mostelectron-rich carbon atom in the ring and is therefore more susceptible to an electrophilic addition.
https://en.wikipedia.org/wiki/File:Pyridine-EAS-4-position-2D-skeletal.pnghttps://en.wikipedia.org/wiki/File:Pyridine-EAS-3-position-2D-skeletal.pnghttps://en.wikipedia.org/wiki/File:Pyridine-EAS-2-position-2D-skeletal.pnghttps://en.wikipedia.org/wiki/Friedel%E2%80%93Crafts_reactionhttps://en.wikipedia.org/wiki/Acylationhttps://en.wikipedia.org/wiki/Alkylationhttps://en.wikipedia.org/wiki/Pyridine#cite_note-jou10-24https://en.wikipedia.org/wiki/Pyridine#cite_note-roempp-4https://en.wikipedia.org/wiki/Nucleophilic_aromatic_substitutionhttps://en.wikipedia.org/wiki/Addition_reactionhttps://en.wikipedia.org/wiki/Electrophilic_substitutionhttps://en.wikipedia.org/wiki/Pyridine#cite_note-78https://en.wikipedia.org/wiki/Aspartic_acidhttps://en.wikipedia.org/wiki/Glyceraldehyde_3-phosphatehttps://en.wikipedia.org/wiki/Escherichia_colihttps://en.wikipedia.org/wiki/Mycobacterium_tuberculosishttps://en.wikipedia.org/wiki/Kynureninehttps://en.wikipedia.org/wiki/Anilinehttps://en.wikipedia.org/wiki/Tryptophanhttps://en.wikipedia.org/wiki/Amino_acidhttps://en.wikipedia.org/wiki/Nicotinic_acidhttps://en.wikipedia.org/wiki/File:Gattermann-Skita_Syntesis.pnghttps://en.wikipedia.org/wiki/Pyridine#cite_note-77https://en.wikipedia.org/wiki/Methylaminehttps://en.wikipedia.org/wiki/Malonic_ester_synthesishttps://en.wikipedia.org/wiki/Pyridine#cite_note-76https://en.wikipedia.org/wiki/File:Ciamician-Dennstedt_Rearrangement.pnghttps://en.wikipedia.org/wiki/Pyridine#cite_note-75https://en.wikipedia.org/wiki/Pyridine#cite_note-74https://en.wikipedia.org/wiki/Pyridine#cite_note-73https://en.wikipedia.org/wiki/Pyridine#cite_note-72https://en.wikipedia.org/wiki/Dichlorocarbenehttps://en.wikipedia.org/wiki/Pyrrolehttps://en.wikipedia.org/wiki/File:Kr%C3%B6hnke_Pyridine_Synthesis.png


8/15



Structure of

pyridine-Noxide

Substitutions to pyridine at the 2- or 4-position result in an energetically unfavorable complex. They can be promoted, however, usingclever experimental techniques, such as conducting electrophilic substitution on the pyridine-N-oxide followed by deoxygenation of thenitrogen atom. Addition of oxygen reduces electron density on the nitrogen atom and promotes substitution at the 2-and 4-carbons. The oxygen atom can then be removed via several routes, most commonly with compounds oftrivalent phosphorus or divalent sulfur which are easily oxidized. Triphenylphosphine is a frequently used reagent,which is oxidized in this reaction to triphenylphosphine oxide. The following paragraphs describe representativeelectrophilic substitution reactions of pyridine.[24]

Direct nitration of pyridine requires harsh conditions and has very low yields. The 3-nitropyridine can be obtained

instead by reacting pyridine with dinitrogen pentoxide in presence of sodium.[79][80][81]

Pyridine derivatives where thenitrogen atom is screened sterically and/or electronically can be obtained by nitration with nitronium tetrafluoroborate(NO2BF4). In this way, 3-nitropyridine can be obtained via the synthesis of 2,6-dibromopyridine followed by

removal of the bromine atoms.[82][83] Direct sulfonation of pyridine is even more difficult than direct nitration.However, pyridine-3-sulfonic acid can be obtained at acceptable yield by boiling pyridine in an excess of sulfuric acid at 320 C. [84]

Reaction with the SO3 group also facilitates addition of sulfur to the nitrogen atom, especially in the presence of a mercury(II) sulfate

catalyst.[24][85]

In contrast to the nitration and sulfonation, the direct bromination and chlorination of pyridine proceed well. The reaction of pyridine withmolecular bromine in sulfuric acid at 130 C readily produced 3-bromopyridine. The yield is lower for 3-chloropyridine upon chlorinationwith molecular chlorine in the presence of aluminium chloride at 100 C. Both 2-bromopyridine and 2-chloropyridine can be produced bydirect reaction with halogen with a palladium(II) chloride catalyst.[86]

Nucleophilic substitutions

In contrast to benzene, pyridine efficiently supports several nucleophilic substitutions, and is regarded as a good nucleophile (donor number33.1). The reason for this is relatively lower electron density of the carbon atoms of the ring. These reactions include substitutions withelimination of a hydride ion and elimination-additions with formation of an intermediate aryne configuration, and usually proceed at 2- or 4-

position.[24][25]

Many nucleophilic substitutions occur easier not with bare pyridine, but with pyridine modified with bromine, chlorine, fluorine or sulfonic

acid fragments which then become a leaving group. So fluorine is the best leaving group for the substitution with organolithium compounds.The nucleophilic attack compounds may be alkoxides, thiolates, amines, and ammonia (at elevated pressures).[87]

The hydride ion is generally a poor leaving group and occurs only in a few heterocyclic reactions. They include the Chichibabin reactionwhich yields pyridine derivatives aminated at the 2-position. Here sodium amide is used as the nucleophile yielding 2-aminopyridine. Thehydride ion released in this reaction combines with a proton of an available amino group forming a hydrogen molecule.[25][88]

Analogous to benzene, nucleophilic substitutions to pyridine can result in the formation of pyridyne intermediates as heteroaryne. For thispurpose, pyridine derivatives can be eliminated with good leaving groups using strong bases such as sodium and potassium tert-butoxide.The subsequent addition of a nucleophile to the triple bond has low selectivity and the result is a mixture of the two possible adducts. [24]

Radical reactions

Pyridine supports a series of radical reactions, which is used in its dimerization to bipyridines. Radical dimerization of pyridine withelemental sodium or Raney nickel selectively yields 4,4'-bipyridine[89] or 2,2'-bipyridine,[90] which are important precursor reagents in thechemical industry. One of the name reactions involving free radicals is the Minisci reaction. It can produce 2-tert-butylpyridine uponreacting pyridine with pivalic acid, silver nitrate and ammonium in sulfuric acid with a yield of 97%. [24]
https://en.wikipedia.org/wiki/Pyridine#cite_note-jou10-24https://en.wikipedia.org/wiki/Sulfuric_acidhttps://en.wikipedia.org/wiki/Ammoniumhttps://en.wikipedia.org/wiki/Silver_nitratehttps://en.wikipedia.org/wiki/Pivalic_acidhttps://en.wikipedia.org/wiki/Minisci_reactionhttps://en.wikipedia.org/wiki/Name_reactionshttps://en.wikipedia.org/wiki/Pyridine#cite_note-90https://en.wikipedia.org/wiki/2,2%27-bipyridinehttps://en.wikipedia.org/wiki/Pyridine#cite_note-89https://en.wikipedia.org/wiki/4,4%27-bipyridinehttps://en.wikipedia.org/wiki/Raney_nickelhttps://en.wikipedia.org/wiki/Sodiumhttps://en.wikipedia.org/wiki/Dimer_(chemistry)https://en.wikipedia.org/wiki/Pyridine#cite_note-jou10-24https://en.wikipedia.org/wiki/Triple_bondhttps://en.wikipedia.org/wiki/Potassium_tert-butoxidehttps://en.wikipedia.org/wiki/Arynehttps://en.wikipedia.org/wiki/Pyridynehttps://en.wikipedia.org/wiki/Pyridine#cite_note-88https://en.wikipedia.org/wiki/Pyridine#cite_note-davies-25https://en.wikipedia.org/wiki/Sodium_amidehttps://en.wikipedia.org/wiki/Aminationhttps://en.wikipedia.org/wiki/Chichibabin_reactionhttps://en.wikipedia.org/wiki/Pyridine#cite_note-87https://en.wikipedia.org/wiki/Aminehttps://en.wikipedia.org/wiki/Alkoxidehttps://en.wikipedia.org/wiki/Organolithium_compoundhttps://en.wikipedia.org/wiki/File:Pyridine-NA-4-position.svghttps://en.wikipedia.org/wiki/File:Pyridine-NA-3-position.svghttps://en.wikipedia.org/wiki/File:Pyridine-NA-2-position.svghttps://en.wikipedia.org/wiki/Pyridine#cite_note-davies-25https://en.wikipedia.org/wiki/Pyridine#cite_note-jou10-24https://en.wikipedia.org/wiki/Arynehttps://en.wikipedia.org/wiki/Hydridehttps://en.wikipedia.org/wiki/Donor_numberhttps://en.wikipedia.org/wiki/Nucleophilehttps://en.wikipedia.org/wiki/Pyridine#cite_note-86https://en.wikipedia.org/wiki/Palladium(II)_chloridehttps://en.wikipedia.org/wiki/Aluminium_chloridehttps://en.wikipedia.org/wiki/Chlorinehttps://en.wikipedia.org/wiki/Brominehttps://en.wikipedia.org/wiki/Halogenationhttps://en.wikipedia.org/wiki/Brominationhttps://en.wikipedia.org/wiki/Pyridine#cite_note-85https://en.wikipedia.org/wiki/Pyridine#cite_note-jou10-24https://en.wikipedia.org/wiki/Mercury(II)_sulfatehttps://en.wikipedia.org/wiki/Pyridine#cite_note-84https://en.wikipedia.org/wiki/Sulfuric_acidhttps://en.wikipedia.org/wiki/Sulfonationhttps://en.wikipedia.org/wiki/Pyridine#cite_note-83https://en.wikipedia.org/wiki/Pyridine#cite_note-82https://en.wikipedia.org/wiki/Nitronium_tetrafluoroboratehttps://en.wikipedia.org/wiki/Pyridine#cite_note-81https://en.wikipedia.org/wiki/Pyridine#cite_note-80https://en.wikipedia.org/wiki/Pyridine#cite_note-79https://en.wikipedia.org/wiki/Sodiumhttps://en.wikipedia.org/wiki/Dinitrogen_pentoxidehttps://en.wikipedia.org/wiki/Nitrationhttps://en.wikipedia.org/wiki/Pyridine#cite_note-jou10-24https://en.wikipedia.org/wiki/Triphenylphosphine_oxidehttps://en.wikipedia.org/wiki/Triphenylphosphinehttps://en.wikipedia.org/wiki/Sulfurhttps://en.wikipedia.org/wiki/Phosphorushttps://en.wikipedia.org/wiki/File:Pyridine_N-oxide.png


9/15



Additions of various Lewis acids to pyridine

Reduction of pyridine to piperidine

with Raney nickel

Use of pyridine in the

chemical industry, VEB

Berlin-Chemie, 1959.

Reactions on the nitrogen atom

Lewis acids easily add to the nitrogen atom of pyridine forming pyridiniumsalts. The reaction with alkylhalides leads to alkylation of the nitrogen atom.This creates a positive charge in the ring that increases the reactivity of

pyridine to both oxidation and reduction. The Zincke reaction is used forthe selective introduction of radicals in pyridinium compounds (it has norelation to the chemical element zinc).

Hydrogenation and reduction

Hydrogen-saturated piperidine isobtained through reaction with hydrogen gas in the presence of Raney nickel. [91] This reactionreleases 193.8 kJmol1 of energy,[92] which is slightly less than the energy of the hydrogenationof benzene (205.3 kJmol1).[92]

Partially hydrogenated derivatives are obtained under milder conditions. For example, reductionwith lithium aluminium hydride yields a mixture of 1,4-dihydropyridine, 1,2-dihydropyridine and2,5-dihydropyridine.[93] Selective synthesis of 1,4-dihydropyridine is achieved in the presence of

organometallic complexes of magnesium and zinc,[94] and (3,4)-tetrahydropyridine is obtained by electrochemical reduction ofpyridine.[95]

Applications

Pyridine is an important raw material in of the chemical industry, with the 1989 production of 26,000tonnes in world-wide.[45] Among major 25 production sites for pyridine eleven are located in Europe (asof 1999).[22] The major producers of pyridine include Evonik Industries, Rtgers Chemicals, ImperialChemical Industries and Koei Chemical.[45] The pyridine production has significantly increased in theearly 2000s, with an annual production capacity of 30,000 tonnes in mainland China alone.[96] The US-Chinese joint venture Vertellus is currently the world leader in pyridine production. [97]

Pyridine is used as polar, basic, low-reactive solvent, for example in Knoevenagel condensations. [22] It isespecially suitable for the dehalogenation, where it acts as the base of the elimination reaction and bondsthe resulting hydrogen halide to form a pyridinium salt. In esterifications and acylations pyridine activatesthe carboxylic acid halides or anhydrides. Even more active in these reactions are the pyridine derivatives4-dimethylaminopyridine (DMAP) and 4-(1-pyrrolidinyl) pyridine. Pyridine is also used as a base incondensation reactions.[98]

Elimination reaction with pyridine to form pyridinium

Pyridinium chlorochromate was developed by Elias James Corey and William Suggs in 1975 and is used to oxidize primary alcohols toaldehydes and secondary alcohols to ketones.[99] It is obtained by adding pyridine to a solution of chromic acid and concentratedhydrochloric acid:

C5H5N + HCl + CrO3 [C5H5NH][CrO3Cl]

The carcinogenicity of the side-product chromyl chloride (CrO2Cl2) urged to look for alternative routes, such as treating chromium(VI)

oxide with pyridinium chloride:[100]

[C5H5NH+]Cl + CrO3 [C5H5NH][CrO3Cl]

The Cornforth reagent (pyridinium dichromate, PDC),[101] pyridinium chlorochromate (PCC), the Collins reagent (complex ofchromium(VI) oxide with pyridine in dichloromethane)[102][103] and the Sarret reagent (complex of chromium(VI) oxide with pyridine in

pyridine) are similar chromium-based pyridine compounds, which are also used for oxidation, namely conversion of primary and secondary
https://en.wikipedia.org/wiki/Primary_alcoholhttps://en.wikipedia.org/wiki/Chromium_trioxidehttps://en.wikipedia.org/wiki/Pyridine#cite_note-103https://en.wikipedia.org/wiki/Pyridine#cite_note-102https://en.wikipedia.org/wiki/Dichloromethanehttps://en.wikipedia.org/wiki/Chromium_trioxidehttps://en.wikipedia.org/wiki/Collins_reagenthttps://en.wikipedia.org/wiki/Pyridinium_chlorochromatehttps://en.wikipedia.org/wiki/Pyridine#cite_note-101https://en.wikipedia.org/wiki/Cornforth_reagenthttps://en.wikipedia.org/wiki/Pyridine#cite_note-100https://en.wikipedia.org/wiki/Chromium(VI)_oxidehttps://en.wikipedia.org/wiki/Chromyl_chloridehttps://en.wikipedia.org/wiki/Hydrochloric_acidhttps://en.wikipedia.org/wiki/Chromic_acidhttps://en.wikipedia.org/wiki/Pyridine#cite_note-corey-99https://en.wikipedia.org/wiki/Ketoneshttps://en.wikipedia.org/wiki/Alcoholshttps://en.wikipedia.org/wiki/Aldehydeshttps://en.wikipedia.org/wiki/Alcoholshttps://en.wikipedia.org/wiki/Oxidizehttps://en.wikipedia.org/wiki/Elias_James_Coreyhttps://en.wikipedia.org/wiki/Pyridinium_chlorochromatehttps://en.wikipedia.org/wiki/File:Chlorocyclopentane_elimination.svghttps://en.wikipedia.org/wiki/Pyridine#cite_note-98https://en.wikipedia.org/wiki/Condensation_reactionhttps://en.wikipedia.org/wiki/4-dimethylaminopyridinehttps://en.wikipedia.org/wiki/Carboxylic_acidhttps://en.wikipedia.org/wiki/Esterificationhttps://en.wikipedia.org/wiki/Elimination_reactionhttps://en.wikipedia.org/wiki/Pyridine#cite_note-osha-22https://en.wikipedia.org/wiki/Knoevenagel_condensationhttps://en.wikipedia.org/wiki/Pyridine#cite_note-97https://en.wikipedia.org/w/index.php?title=Vertellus&action=edit&redlink=1https://en.wikipedia.org/wiki/Pyridine#cite_note-96https://en.wikipedia.org/wiki/Pyridine#cite_note-ul-45https://en.wikipedia.org/wiki/Imperial_Chemical_Industrieshttps://en.wikipedia.org/wiki/Evonik_Industrieshttps://en.wikipedia.org/wiki/Pyridine#cite_note-osha-22https://en.wikipedia.org/wiki/Pyridine#cite_note-ul-45https://en.wikipedia.org/wiki/Chemical_industryhttps://en.wikipedia.org/wiki/Pyridine#cite_note-95https://en.wikipedia.org/wiki/Pyridine#cite_note-94https://en.wikipedia.org/wiki/Zinchttps://en.wikipedia.org/wiki/Magnesiumhttps://en.wikipedia.org/wiki/Pyridine#cite_note-93https://en.wikipedia.org/wiki/Lithium_aluminium_hydridehttps://en.wikipedia.org/wiki/Pyridine#cite_note-Cox-92https://en.wikipedia.org/wiki/Benzenehttps://en.wikipedia.org/wiki/Pyridine#cite_note-Cox-92https://en.wikipedia.org/wiki/Pyridine#cite_note-91https://en.wikipedia.org/wiki/Raney_nickelhttps://en.wikipedia.org/wiki/Zinchttps://en.wikipedia.org/wiki/Zincke_reactionhttps://en.wikipedia.org/wiki/Alkylationhttps://en.wikipedia.org/w/index.php?title=Alkylhalide&action=edit&redlink=1https://en.wikipedia.org/wiki/Lewis_acidhttps://en.wikipedia.org/wiki/File:Bundesarchiv_Bild_183-62018-0003,_Produktionsverpflichtungen_im_VEB_Berlin-Chemie.jpghttps://en.wikipedia.org/wiki/Raney_nickelhttps://en.wikipedia.org/wiki/File:Pyridine_hydrogenation.pnghttps://en.wikipedia.org/wiki/Lewis_acidhttps://en.wikipedia.org/wiki/File:Pyridine-complex.png


10/15



Oxidation of an alcohol to aldehydewith the Collins reagent.

structure of the Crabtree's c atalyst

alcohols to ketones. The Collins and Sarret reagents are both difficult and dangerous to prepare, they are hygroscopic and can inflameduring preparation. For this reason, the use of PCC and PDC was preferred. Those reagents were rather popular in the 1970s1980s, but

because of their toxicity and confirmed carcinogenic status, they are rarely used nowadays.[104]

When a pyridine ligand is part of a metal complex, it can be easily replaced by a strongerchelating Lewis base. This property is exploited in catalysis of polymerization[105][106] andhydrogenation reactions, using, for example, the Crabtree's catalyst.[107] The pyridine ligandreplaced during the reaction is restored after its completion.

In the pharmaceutical industry pyridine serves as a building block for making a variety of drugs,insecticides and herbicides. It was and is used in large quantities in the production of herbicidesdiquat and paraquat, which contain bipyridine fragments. The first synthesis step of insecticidechlorpyrifos consists of the chlorination of pyridine. Pyridine is also the starting compound for the

preparation of pyrithione-based fungicides.[22] Cetylpyridinium and laurylpyridinium, which canbe produced from pyridine with a Zincke reaction, are used as antiseptic in oral and dental careproducts.[4]

Synthesis of paraquat[108]

In addition to pyridines, piperidine derivatives are also important synthetic building blocks. A common synthesis of piperidine is thereduction of pyridine with a nickel, cobalt or ruthenium-based catalyst at elevated temperatures. [109]

Pyridine is used as a solvent in the manufacture of dyes and rubber. [110] It is also used in the textile industry to improve network capacity ofcotton.[4] Pyridine is added to ethanol to make it unsuitable for drinking.[4] In low doses, pyridine is added to foods to give them a bitterflavor, and such usage is approved by the US Food and Drug Administration. [22] The detection threshold for pyridine in solutions is about

13 mmoleL1 (79237 mgL1).[111] As a base, pyridine can be used as the Karl Fischer reagent, but it is usually replaced byalternatives with a more pleasant odor, such as imidazole.[112]

Pyridine is widely used as a ligand in coordination chemistry. Also important are its chelating derivatives 2,2'-bipyridine, consisting of twopyridine molecules joined by a single bond, and terpyridine, a molecule of three pyridine rings linked together. Pyridine is easily attacked byalkylating agents to giveN-alkylpyridinium salts. One example is cetylpyridinium chloride, a cationic surfactant that is a widely useddisinfection and antiseptic agent. Pyridinium salts can be obtained in the Zincke reaction. Useful adducts of pyridine include pyridine-

borane, C5H5NBH3 (melting point 1011 C), a mild reducing agent with improved stability relative to NaBH4 in protic solvents andimproved solubility in aprotic organic solvents. Pyridine-sulfur trioxide, C5H5NSO3 (melting point 175 C) is a sulfonation agent used toconvert alcohols to sulfonates, which in turn undergo C-O bond scission upon reduction with hydride agents.

Hazards

Pyridine has a flash point (the lowest temperature at which it can vaporize to form an ignitable mixture in air) of only 17 C and is thereforehighly flammable. Its ignition temperature is 550 C, and mixtures of 1.710.6 vol% of pyridine with air are explosive. The thermalmodification of pyridine starts above 490 C, resulting in bipyridine (mainly 2,2'-bipyridine and to a lesser extent 2,3'-bipyridine and 2,4'-

bipyridine), nitrogen oxides and carbon monoxide.[14] Pyridine easily dissolves in water and harms both animals and plants in aquaticsystems.[113] The permitted maximum allowable concentration of pyridine was 1530 parts per million (ppm, or 1530 mgm3 in air) inmost countries in the 1990s,[22] but was reduced to 5 ppm in the 2000s.[114] For comparison, indoor air contaminated with tobaccosmoke may contain up to 16 gm3, and one cigarette contains 2132 g of pyridine.[22]

Health issues

Pyridine is harmful if inhaled, swallowed or absorbed through the skin.[115] Effects of acute pyridine intoxication include dizziness,headache, lack of coordination, nausea, salivation and loss of appetite. They may progress into abdominal pain, pulmonary congestion andunconsciousness.[116] One person died after accidental ingestion of half a cup of pyridine. [22] The lowest known lethal dose (LDLo) for the

ingestion of pyridine in humans is 500 mgkg1. In high doses pyridine has a narcotic effect and its vapor concentrations of above 3600ppm pose a health risk.[45] The oral LD50 in rats is 891 mgkg

1. Pyridine is flammable.
https://en.wikipedia.org/wiki/Median_lethal_dosehttps://en.wikipedia.org/wiki/Pyridine#cite_note-ul-45https://en.wikipedia.org/wiki/Parts_per_millionhttps://en.wikipedia.org/wiki/Lethal_dosehttps://en.wikipedia.org/wiki/Pyridine#cite_note-osha-22https://en.wikipedia.org/wiki/Pyridine#cite_note-IARC1-116https://en.wikipedia.org/wiki/Salivahttps://en.wikipedia.org/wiki/Ataxiahttps://en.wikipedia.org/wiki/Pyridine#cite_note-Aylward-115https://en.wikipedia.org/wiki/Pyridine#cite_note-osha-22https://en.wikipedia.org/wiki/Pyridine#cite_note-114https://en.wikipedia.org/wiki/Pyridine#cite_note-osha-22https://en.wikipedia.org/wiki/Threshold_limit_valuehttps://en.wikipedia.org/wiki/Pyridine#cite_note-113https://en.wikipedia.org/wiki/Pyridine#cite_note-GESTIS-14https://en.wikipedia.org/wiki/Carbon_monoxidehttps://en.wikipedia.org/wiki/Nitrogen_oxidehttps://en.wikipedia.org/wiki/Bipyridinehttps://en.wikipedia.org/wiki/Flash_pointhttps://en.wikipedia.org/wiki/Beta_scissionhttps://en.wikipedia.org/wiki/Carbon-oxygen_bondhttps://en.wikipedia.org/wiki/Sulfonationhttps://en.wikipedia.org/wiki/Sulfur_trioxide_pyridine_complexhttps://en.wikipedia.org/wiki/Boranehttps://en.wikipedia.org/wiki/Adducthttps://en.wikipedia.org/wiki/Zincke_reactionhttps://en.wikipedia.org/wiki/Antiseptichttps://en.wikipedia.org/wiki/Disinfectionhttps://en.wikipedia.org/wiki/Cationic_surfactanthttps://en.wikipedia.org/wiki/Cetylpyridinium_chloridehttps://en.wikipedia.org/wiki/Terpyridinehttps://en.wikipedia.org/wiki/Bipyridinehttps://en.wikipedia.org/wiki/Coordination_chemistryhttps://en.wikipedia.org/wiki/Ligandhttps://en.wikipedia.org/wiki/Pyridine#cite_note-112https://en.wikipedia.org/wiki/Imidazolehttps://en.wikipedia.org/wiki/Karl_Fischer_titrationhttps://en.wikipedia.org/wiki/Pyridine#cite_note-111https://en.wikipedia.org/wiki/Mole_(unit)https://en.wikipedia.org/wiki/Pyridine#cite_note-osha-22https://en.wikipedia.org/wiki/Food_and_Drug_Administrationhttps://en.wikipedia.org/wiki/Pyridine#cite_note-roempp-4https://en.wikipedia.org/wiki/Ethanolhttps://en.wikipedia.org/wiki/Pyridine#cite_note-roempp-4https://en.wikipedia.org/wiki/Pyridine#cite_note-110https://en.wikipedia.org/wiki/Pyridine#cite_note-109https://en.wikipedia.org/wiki/Rutheniumhttps://en.wikipedia.org/wiki/Cobalthttps://en.wikipedia.org/wiki/Piperidinehttps://en.wikipedia.org/wiki/Pyridine#cite_note-108https://en.wikipedia.org/wiki/Paraquathttps://en.wikipedia.org/wiki/File:Synthesis_of_paraquat.pnghttps://en.wikipedia.org/wiki/Pyridine#cite_note-roempp-4https://en.wikipedia.org/wiki/Antiseptichttps://en.wikipedia.org/wiki/Cetylpyridinium_chloridehttps://en.wikipedia.org/wiki/Pyridine#cite_note-osha-22https://en.wikipedia.org/wiki/Fungicidehttps://en.wikipedia.org/w/index.php?title=Pyrithione&action=edit&redlink=1https://en.wikipedia.org/wiki/Chlorpyrifoshttps://en.wikipedia.org/wiki/Paraquathttps://en.wikipedia.org/wiki/Diquathttps://en.wikipedia.org/wiki/Herbicidehttps://en.wikipedia.org/wiki/Insecticidehttps://en.wikipedia.org/wiki/Pyridine#cite_note-107https://en.wikipedia.org/wiki/Crabtree%27s_catalysthttps://en.wikipedia.org/wiki/Pyridine#cite_note-106https://en.wikipedia.org/wiki/Pyridine#cite_note-105https://en.wikipedia.org/wiki/Polymerizationhttps://en.wikipedia.org/wiki/Pyridine#cite_note-b1-104https://en.wikipedia.org/wiki/Ketonehttps://en.wikipedia.org/wiki/Crabtree%27s_catalysthttps://en.wikipedia.org/wiki/File:Crabtree.svghttps://en.wikipedia.org/wiki/Collins_reagenthttps://en.wikipedia.org/wiki/File:Collins_reagent.png


11/15



Metabolism of pyridine

Evaluations as a possible carcinogenic agent showed there is inadequate evidence in humans for the carcinogenicity of pyridine, albeit thereis limited evidence of carcinogenic effects on animals.[116] Available data indicate that "exposure to pyridine in drinking-water led toreduction of sperm motility at all dose levels in mice and increased estrous cycle length at the highest dose level in rats".[116]

Pyridine might also have minor neurotoxic, genotoxic and clastogenic effects.[14][22][117] Exposure to pyridine would normally lead to itsinhalation and absorption in the lungs and gastrointestinal tract,where it either remains unchanged or is metabolized. The major

products of pyridine metabolism areN-methylpyridiniumhydroxide,which is formed by N-methyltransferases (e.g. pyridine N-

methyltransferase), as well as pyridine-Noxide, and 2-, 3- and 4-hydroxypyridine, which are generated by the action ofmonooxygenase. In humans, pyridine is metabolized only intoN-methylpyridiniumhydroxide.[14][117] Pyridine is readily degraded by

bacteria to ammonia and carbon dioxide.[118] The unsubstitutedpyridine ring degrades more rapidly than picoline, lutidine,chloropyridine, or aminopyridines,[119] and a number of pyridinedegraders have been shown to overproduce riboflavin in the

presence of pyridine.[120]

Minor amounts of pyridine are released into environment fromsome industrial processes such as steel manufacture,[121]

processing of oil shale, coal gasification, coking plants and incinerators.[22] The atmosphere at oil shale processing plants can containpyridine concentrations of up to 13 gm3,[122] and 53 gm3 levels were measured in the groundwater in the vicinity of a coalgasification plant.[123] According to a study by the US National Institute for Occupational Safety and Health, about 43,000 Americanswork in contact with pyridine.[124]

See also

6-membered aromatic rings with one carbon replaced by another group: borabenzene, benzene, silabenzene, germabenzene,stannabenzene, pyridine , phosphorine, arsabenzene, pyrylium salt6-membered rings with two nitrogen atoms: diazines6-membered rings with three nitrogen atoms: triazines

6-membered rings with four nitrogen atoms: tetrazines6-membered rings with six nitrogen atoms: hexazine

References

1. ^ Lide, p. 3-4742. ^ Linnell, Robert (1960). Journal of Organic Chemistry25 (2): 290. doi:10.1021/jo01072a623 (http://dx.doi.org/10.1021%2Fjo01072a623).3. ^ Pearson, Ralph G.; Williams, Forrest V. (1953). Journal of the American Chemical Society75 (13): 3073. doi:10.1021/ja01109a008

(http://dx.doi.org/10.1021%2Fja01109a008).

4. ^ abcdef "RMPP Online Version 3.5". Thieme Chemistry (Stuttgart: Georg Thieme). 2009.5. ^ Pyridine MSDS (https://fscimage.fishersci.com/msds/19990.htm). fishersci.com

6. ^ "Iodine Solution (0.02M in THF/pyridine/H2O 70:20:10)" (http://www.sigmaaldrich.com/catalog/ProductDetail.do?D7=0&N5=SEARCH_CONCAT_PNO%7CBRAND_KEY&N4=59706%7CFLUKA&N25=0&QS=ON&F=SPEC). Sigma-Aldrich. Retrieved28 November 2011.

7. ^ Pyridine (http://www.britannica.com/EBchecked/topic/484880/pyridine). Encyclopdia Britannica on-line

8. ^ ab Lide, p. 3448

9. ^ ab Mootz, D. (1981). "Crystal structures of pyridine and pyridine trihydrate". The Journal of Chemical Physics75 (3): 1517.Bibcode:1981JChPh..75.1517M (http://adsabs.harvard.edu/abs/1981JChPh..75.1517M). doi:10.1063/1.442204(http://dx.doi.org/10.1063%2F1.442204).

10. ^ Lide, p. 367311. ^ Lide, p. 5-2812. ^ Lide, p. 6-21113. ^ Lide, p. 6221

14. ^ abcdRecord ofPyridine (http://gestis-en.itrust.de/nxt/gateway.dll?f=id$t=default.htm$vid=gestiseng:sdbeng$id=013850) in the GESTIS

Substance Database from the IFA15. ^ Majer, V. and Svoboda, V. (1985). Enthalpies of Vaporization of Organic Compounds: A Critical Review and Data Compilation,

Blackwell Scientific Publications, Oxford, ISBN 0-632-01529-216. ^ Domalski, Eugene S.; Hearing, Elizabeth D. (1996). "Heat Capacities and Entropies of Organic Compounds in the Condensed Phase".

Journal of Physical and Chemical Reference Data25: 1. Bibcode:1996JPCRD..25....1D(http://adsabs.harvard.edu/abs/1996JPCRD..25....1D). doi:10.1063/1.555985 (http://dx.doi.org/10.1063%2F1.555985).
http://dx.doi.org/10.1063%2F1.555985https://en.wikipedia.org/wiki/Digital_object_identifierhttp://adsabs.harvard.edu/abs/1996JPCRD..25....1Dhttps://en.wikipedia.org/wiki/Bibcodehttps://en.wikipedia.org/wiki/Pyridine#cite_ref-16https://en.wikipedia.org/wiki/Special:BookSources/0632015292https://en.wikipedia.org/wiki/Pyridine#cite_ref-Majer_Svoboda_15-0https://en.wikipedia.org/wiki/Institute_for_Occupational_Safety_and_Healthhttp://gestis-en.itrust.de/nxt/gateway.dll?f=id$t=default.htm$vid=gestiseng:sdbeng$id=013850https://en.wikipedia.org/wiki/Pyridine#cite_ref-GESTIS_14-3https://en.wikipedia.org/wiki/Pyridine#cite_ref-GESTIS_14-2https://en.wikipedia.org/wiki/Pyridine#cite_ref-GESTIS_14-1https://en.wikipedia.org/wiki/Pyridine#cite_ref-GESTIS_14-0https://en.wikipedia.org/wiki/Pyridine#Lidehttps://en.wikipedia.org/wiki/Pyridine#cite_ref-13https://en.wikipedia.org/wiki/Pyridine#Lidehttps://en.wikipedia.org/wiki/Pyridine#cite_ref-12https://en.wikipedia.org/wiki/Pyridine#Lidehttps://en.wikipedia.org/wiki/Pyridine#cite_ref-lide528_11-0https://en.wikipedia.org/wiki/Pyridine#Lidehttps://en.wikipedia.org/wiki/Pyridine#cite_ref-10http://dx.doi.org/10.1063%2F1.442204https://en.wikipedia.org/wiki/Digital_object_identifierhttp://adsabs.harvard.edu/abs/1981JChPh..75.1517Mhttps://en.wikipedia.org/wiki/Bibcodehttps://en.wikipedia.org/wiki/Pyridine#cite_ref-str_9-1https://en.wikipedia.org/wiki/Pyridine#cite_ref-str_9-0https://en.wikipedia.org/wiki/Pyridine#Lidehttps://en.wikipedia.org/wiki/Pyridine#cite_ref-lide3448_8-1https://en.wikipedia.org/wiki/Pyridine#cite_ref-lide3448_8-0http://www.britannica.com/EBchecked/topic/484880/pyridinehttps://en.wikipedia.org/wiki/Pyridine#cite_ref-brit_7-0http://www.sigmaaldrich.com/catalog/ProductDetail.do?D7=0&N5=SEARCH_CONCAT_PNO%7CBRAND_KEY&N4=59706%7CFLUKA&N25=0&QS=ON&F=SPEChttps://en.wikipedia.org/wiki/Pyridine#cite_ref-Pyridine_Solution_in_DNA_Synthesis_6-0https://fscimage.fishersci.com/msds/19990.htmhttps://en.wikipedia.org/wiki/Pyridine#cite_ref-5https://en.wikipedia.org/wiki/Pyridine#cite_ref-roempp_4-5https://en.wikipedia.org/wiki/Pyridine#cite_ref-roempp_4-4https://en.wikipedia.org/wiki/Pyridine#cite_ref-roempp_4-3https://en.wikipedia.org/wiki/Pyridine#cite_ref-roempp_4-2https://en.wikipedia.org/wiki/Pyridine#cite_ref-roempp_4-1https://en.wikipedia.org/wiki/Pyridine#cite_ref-roempp_4-0http://dx.doi.org/10.1021%2Fja01109a008https://en.wikipedia.org/wiki/Digital_object_identifierhttps://en.wikipedia.org/wiki/Pyridine#cite_ref-3http://dx.doi.org/10.1021%2Fjo01072a623https://en.wikipedia.org/wiki/Digital_object_identifierhttps://en.wikipedia.org/wiki/Pyridine#cite_ref-2https://en.wikipedia.org/wiki/Pyridine#Lidehttps://en.wikipedia.org/wiki/Pyridine#cite_ref-1https://en.wikipedia.org/wiki/Hexazinehttps://en.wikipedia.org/wiki/Tetrazinehttps://en.wikipedia.org/wiki/Triazinehttps://en.wikipedia.org/wiki/Diazinehttps://en.wikipedia.org/wiki/Pyrylium_salthttps://en.wikipedia.org/wiki/Arsabenzenehttps://en.wikipedia.org/wiki/Phosphorinehttps://en.wikipedia.org/wiki/Stannabenzenehttps://en.wikipedia.org/wiki/Germabenzenehttps://en.wikipedia.org/wiki/Silabenzenehttps://en.wikipedia.org/wiki/Benzenehttps://en.wikipedia.org/wiki/Borabenzenehttps://en.wikipedia.org/wiki/Pyridine#cite_note-124https://en.wikipedia.org/wiki/National_Institute_for_Occupational_Safety_and_Healthhttps://en.wikipedia.org/wiki/Pyridine#cite_note-123https://en.wikipedia.org/wiki/Groundwaterhttps://en.wikipedia.org/wiki/Pyridine#cite_note-122https://en.wikipedia.org/wiki/Pyridine#cite_note-osha-22https://en.wikipedia.org/wiki/Incinerationhttps://en.wikipedia.org/wiki/Oil_shalehttps://en.wikipedia.org/wiki/Pyridine#cite_note-121https://en.wikipedia.org/wiki/Pyridine#cite_note-120https://en.wikipedia.org/wiki/Riboflavinhttps://en.wikipedia.org/wiki/Pyridine#cite_note-119https://en.wikipedia.org/wiki/Aminopyridinehttps://en.wikipedia.org/wiki/Chloropyridinehttps://en.wikipedia.org/wiki/Lutidinehttps://en.wikipedia.org/wiki/Picolinehttps://en.wikipedia.org/wiki/Pyridine#cite_note-118https://en.wikipedia.org/wiki/Pyridine#cite_note-bonnard-117https://en.wikipedia.org/wiki/Pyridine#cite_note-GESTIS-14https://en.wikipedia.org/wiki/Monooxygenasehttps://en.wikipedia.org/wiki/Pyridine_N-methyltransferasehttps://en.wikipedia.org/wiki/N-methyltransferasehttps://en.wikipedia.org/wiki/Metabolismhttps://en.wikipedia.org/wiki/Pyridine#cite_note-bonnard-117https://en.wikipedia.org/wiki/Pyridine#cite_note-osha-22https://en.wikipedia.org/wiki/Pyridine#cite_note-GESTIS-14https://en.wikipedia.org/wiki/Clastogenhttps://en.wikipedia.org/wiki/Genotoxicityhttps://en.wikipedia.org/wiki/Neurotoxinhttps://en.wikipedia.org/wiki/Pyridine#cite_note-IARC1-116https://en.wikipedia.org/wiki/Pyridine#cite_note-IARC1-116https://en.wikipedia.org/wiki/Carcinogenichttps://en.wikipedia.org/wiki/File:Pyridin-Metabolisierung.png


12/15



17. ^ Cox, E. (1958). "Crystal Structure of Benzene". Reviews of Modern Physics30: 159. Bibcode:1958RvMP...30..159C(http://adsabs.harvard.edu/abs/1958RvMP...30..159C). doi:10.1103/RevModPhys.30.159(http://dx.doi.org/10.1103%2FRevModPhys.30.159).

18. ^ Lide, p. 66719. ^ McCullough, J. P.; Douslin, D. R.; Messerly, J. F.; Hossenlopp, I. A.; Kincheloe, T. C.; Waddington, Guy (1957). "Pyridine: Experimental

and Calculated Chemical Thermodynamic Properties between 0 and 1500K.; a Revised Vibrational Assignment".Journal of the AmericanChemical Society79 (16): 4289. doi:10.1021/ja01573a014 (http://dx.doi.org/10.1021%2Fja01573a014).

20. ^ Joule, p. 1421. ^ Joule, p. 16

22. ^ abcdefghijkl Pyridine (http://monographs.iarc.fr/ENG/Monographs/vol77/mono77-21.pdf), IARC Monogrpahs Vol. 77, OSHA,

Washington D.C., 198523. ^ Pyridine hydrochloride MSDS (http://www.alfa.com/content/msds/english/L11463.pdf), Alfa Aesar, 26 June 2010

24. ^ abcdefg Joule, pp. 125141

25. ^ abc D. T. Davies Aromatic heterocyclic chemistry, Oxford University Press, 1992, ISBN 0-19-855660-826. ^ R. Milcent, F. Chau: Chimie organique htrocyclique: Structures fondamentales, pp. 241282, EDP Sciences, 2002, ISBN 2-86883-583-

X27. ^ Krygowski, T. M.; Szatyowicz,H. and Zachara, J. E. (2005). "How H-bonding Modifies Molecular Structure and -Electron

Delocalization in the Ring of Pyridine/Pyridinium Derivatives Involved in H-Bond Complexation".J. Org. Chem.70 (22): 885965.doi:10.1021/jo051354h (http://dx.doi.org/10.1021%2Fjo051354h). PMID 16238319 (//www.ncbi.nlm.nih.gov/pubmed/16238319).

28. ^ IUPAC SC-Database (http://www.acadsoft.co.uk/scdbase/scdbase.htm) A comprehensive database of published data on equilibriumconstants of metal complexes and ligands

29. ^ Nakamoto, K. (1997). Infrared and Raman spectra of Inorganic and Coordination compounds. Part A (5th ed.). Wiley. ISBN 0-471-16394-5.

30. ^ Nakamoto, K.Infrared and Raman spectra of Inorganic and Coordination compounds. Part B (5th ed.). p. 24. ISBN 0-471-16392-9.31. ^ Mendham, J.; Denney, R. C.; Barnes, J. D.; Thomas, M. J. K. (2000), Vogel's Quantitative Chemical Analysis (6th ed.), New York:

Prentice Hall, p. 418, ISBN 0-582-22628-732. ^ Elschenbroich, C. Organometallchemie, 6th ed., pp. 524525, Vieweg+Teubner, 2008, ISBN 3-8351-0167-633. ^ Joule, p. 734. ^ Elschenbroich, C. Organometallchemie, 6th ed., p. 218, Vieweg+Teubner, 2008, ISBN 3-8351-0167-635. ^ Weissberger, A.; Klingberg, A., Barnes, R. A.; Brody, F. and Ruby, P.R. Pyridine and its Derivatives, Volume 1, 1960, Interscience Pub.,

New York36. ^ Anderson, T. Transactions of Royal Society of Edinburg, 16 (1849) 123

37. ^ ab Von Anderson, Th. (1849). "Producte der trocknen Destillation thierischer Materien". Annalen der Chemie und Pharmacie70: 32.doi:10.1002/jlac.18490700105 (http://dx.doi.org/10.1002%2Fjlac.18490700105).

38. ^ Anderson, Th. (1851). "Ueber die Producte der trocknen Destillation thierischer Materien".Annalen der Chemie und Pharmacie80: 44.doi:10.1002/jlac.18510800104 (http://dx.doi.org/10.1002%2Fjlac.18510800104).

39. ^ Krner, W. Giorn. academ. Palermo, vol. 5 (1869)40. ^ Dewar, J. Chem. News, 23 (1871) 3841. ^ Albert LadenburgLectures on the history of the development of chemistry since the time of Lavoisier.

(http://www.sciencemadness.org/library/books/lectures_on_the_history_of_the_development_of_chemistry.pdf), pp. 28328742. ^ Bansal, Raj K. Heterocyc lic Chemistry (http://books.google.com/books?id=RH1l_VQcFDQC&pg=PA216), (1999) ISBN 81-224-1212-2,

p. 21643. ^ "A. Henninger, aus Paris. 12. April 1877". Berichte der deutschen chemischen Gesellschaft10: 727. 1877. doi:10.1002/cber.187701001202

(http://dx.doi.org/10.1002%2Fcber.187701001202).

44. ^ ab Tscihtschibabin, A. E. (1924). "ber Kondensation der Aldehyde mit Ammoniak zu Pyr idinebasen"(http://gallica.bnf.fr/ark:/12148/bpt6k90877m/f132.chemindefer). Journal fr Praktische Chemie107: 122. doi:10.1002/prac.19241070110(http://dx.doi.org/10.1002%2Fprac.19241070110).

45. ^ abcdefgS. Shimizu, N. Watanabe, T. Kataoka, T. Shoji, N. Abe, S. Morishita, H. IchimuraPyridine and Pyridine Derivatives, inUllmann's Encyclopedia of Industrial Chemistry, 2005, Wiley-VCH, Weinheim. doi:10.1002/14356007.a22_399

(http://dx.doi.org/10.1002%2F14356007.a22_399)46. ^ Burdock, G. A. (ed.) Fenaroli's Handbook of Flavor Ingredients, Vol. II, 3rd Edition, CRC Press, Boca Raton, 1995, ISBN 0-8493-2710-

547. ^ Tufel, A.; Ternes, W.; Tunger, L. and Zobel, M.:Lebensmittel-Lexikon, 4th ed., p. 450, Behr, 2005, ISBN 3-89947-165-248. ^ Tang, Jian; Jin, Qi Zhang; Shen, Guo Hui; Ho, Chi Tang; Chang, Stephen S. (1983). "Isolation and identification of volatile compounds

from fried chicken".Journal of Agricultural and Food Chemistry31 (6): 1287. doi:10.1021/jf00120a035(http://dx.doi.org/10.1021%2Fjf00120a035).

49. ^ Shibamoto, Takayuki; Kamiya, Yoko; Mihara, Satoru (1981). "Isolation and identification of volatile compounds in cooked meat:sukiyaki".Journal of Agricultural and Food Chemistry29: 57. doi:10.1021/jf00103a015 (http://dx.doi.org/10.1021%2Fjf00103a015).

50. ^ Aeschbacher, HU; Wolleb, U; Lliger, J; Spadone, JC; Liardon, R (1989). "Contribution of coffee aroma constituents to the mutagenicityof c offee".Food and chemical toxicology27 (4): 22732. doi:10.1016/0278-6915(89)90160-9 (http://dx.doi.org/10.1016%2F0278-6915%2889%2990160-9). PMID 2659457 (//www.ncbi.nlm.nih.gov/pubmed/2659457).

51. ^ Buttery, Ron G.; Seifert, Richard M.; Guadagni, Dante G. and Ling, Louisa C. (1971). "Characterization of Volatile Pyrazine and Pyridine

Components of Potato Chips".J Agr Food Chem (Washington, DC: Am Chem Soc) 19 (5): 969971. doi:10.1021/jf60177a020(http://dx.doi.org/10.1021%2Fjf60177a020).

52. ^ Ho, Chi Tang; Lee, Ken N.; Jin, Qi Zhang (1983). "Isolation and identification of volatile flavor compounds in fried bacon". Journal ofAgricultural and Food Chemistry31 (2): 336. doi:10.1021/jf00116a038 (http://dx.doi.org/10.1021%2Fjf00116a038).

53. ^ Dumont, Jean Pierre; Adda, Jacques (1978). "Occurrence of sesquiterpene in mountain cheese volatiles". Journal of Agricultural andFood Chemistry26 (2): 364. doi:10.1021/jf60216a037 (http://dx.doi.org/10.1021%2Fjf60216a037).
http://dx.doi.org/10.1021%2Fjf60216a037https://en.wikipedia.org/wiki/Digital_object_identifierhttps://en.wikipedia.org/wiki/Pyridine#cite_ref-53http://dx.doi.org/10.1021%2Fjf00116a038https://en.wikipedia.org/wiki/Digital_object_identifierhttps://en.wikipedia.org/wiki/Pyridine#cite_ref-52http://dx.doi.org/10.1021%2Fjf60177a020https://en.wikipedia.org/wiki/Digital_object_identifierhttps://en.wikipedia.org/wiki/Pyridine#cite_ref-51https://www.ncbi.nlm.nih.gov/pubmed/2659457https://en.wikipedia.org/wiki/PubMed_Identifierhttp://dx.doi.org/10.1016%2F0278-6915%2889%2990160-9https://en.wikipedia.org/wiki/Digital_object_identifierhttps://en.wikipedia.org/wiki/Food_and_chemical_toxicologyhttps://en.wikipedia.org/wiki/Pyridine#cite_ref-50http://dx.doi.org/10.1021%2Fjf00103a015https://en.wikipedia.org/wiki/Digital_object_identifierhttps://en.wikipedia.org/wiki/Pyridine#cite_ref-49http://dx.doi.org/10.1021%2Fjf00120a035https://en.wikipedia.org/wiki/Digital_object_identifierhttps://en.wikipedia.org/wiki/Pyridine#cite_ref-48https://en.wikipedia.org/wiki/Special:BookSources/3899471652https://en.wikipedia.org/wiki/Pyridine#cite_ref-47https://en.wikipedia.org/wiki/Special:BookSources/0849327105https://en.wikipedia.org/wiki/Pyridine#cite_ref-46http://dx.doi.org/10.1002%2F14356007.a22_399https://en.wikipedia.org/wiki/Digital_object_identifierhttps://en.wikipedia.org/wiki/Pyridine#cite_ref-ul_45-6https://en.wikipedia.org/wiki/Pyridine#cite_ref-ul_45-5https://en.wikipedia.org/wiki/Pyridine#cite_ref-ul_45-4https://en.wikipedia.org/wiki/Pyridine#cite_ref-ul_45-3https://en.wikipedia.org/wiki/Pyridine#cite_ref-ul_45-2https://en.wikipedia.org/wiki/Pyridine#cite_ref-ul_45-1https://en.wikipedia.org/wiki/Pyridine#cite_ref-ul_45-0http://dx.doi.org/10.1002%2Fprac.19241070110https://en.wikipedia.org/wiki/Digital_object_identifierhttp://gallica.bnf.fr/ark:/12148/bpt6k90877m/f132.chemindeferhttps://en.wikipedia.org/wiki/Pyridine#cite_ref-tschi_44-1https://en.wikipedia.org/wiki/Pyridine#cite_ref-tschi_44-0http://dx.doi.org/10.1002%2Fcber.187701001202https://en.wikipedia.org/wiki/Digital_object_identifierhttps://en.wikipedia.org/wiki/Pyridine#cite_ref-43https://en.wikipedia.org/wiki/Special:BookSources/8122412122http://books.google.com/books?id=RH1l_VQcFDQC&pg=PA216https://en.wikipedia.org/wiki/Pyridine#cite_ref-42http://www.sciencemadness.org/library/books/lectures_on_the_history_of_the_development_of_chemistry.pdfhttps://en.wikipedia.org/wiki/Albert_Ladenburghttps://en.wikipedia.org/wiki/Pyridine#cite_ref-41https://en.wikipedia.org/wiki/Pyridine#cite_ref-40https://en.wikipedia.org/wiki/Pyridine#cite_ref-39http://dx.doi.org/10.1002%2Fjlac.18510800104https://en.wikipedia.org/wiki/Digital_object_identifierhttps://en.wikipedia.org/wiki/Pyridine#cite_ref-anderson2_38-0

pyridine - wikipedia, the free encyclopedia

Documents