Pyridine

Not to be confused with Pyrimidine or Pyridyne.

Pyridine
Full structural formula of pyridine
Full structural formula of pyridine
Skeletal formula of pyridine, showing the numbering convention
Skeletal formula of pyridine, showing the numbering convention
Ball-and-stick diagram of pyridine
Ball-and-stick diagram of pyridine
Space-filling model of pyridine
Space-filling model of pyridine
Names
Preferred IUPAC name
Pyridine[1]
Systematic IUPAC name
Azabenzene
Other names
Azine
Azinine
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.003.464 Edit this at Wikidata
EC Number
  • 203-809-9
KEGG
UNII
  • InChI=1S/C5H5N/c1-2-4-6-5-3-1/h1-5H checkY
    Key: JUJWROOIHBZHMG-UHFFFAOYSA-N checkY
  • InChI=1/C5H5N/c1-2-4-6-5-3-1/h1-5H
    Key: JUJWROOIHBZHMG-UHFFFAOYAY
  • c1ccncc1
Properties
C5H5N
Molar mass 79.102 g·mol−1
Appearance Colorless liquid[2]
Odor Nauseating, fish-like[3]
Density 0.9819 g/mL (20 °C)[4]
Melting point −41.63 °C (−42.93 °F; 231.52 K)[4]
Boiling point 115.2 °C (239.4 °F; 388.3 K)[4]
Miscible[4]
log P 0.65[5]
Vapor pressure 16 mmHg (20 °C)[3]
Acidity (pKa) 5.23 (pyridinium)[6]
Conjugate acid Pyridinium
−48.7·10−6 cm3/mol[7]
Thermal conductivity 0.166 W/(m·K)[8]
1.5095 (20 °C)[4]
Viscosity 0.879 cP (25 °C)[9]
2.215 D[10]
Thermochemistry[11]
132.7 J/(mol·K)
100.2 kJ/mol
−2.782 MJ/mol
Hazards[15]
Occupational safety and health (OHS/OSH):
Main hazards
 Low to moderate hazard[13]
GHS labelling:
GHS02: FlammableGHS07: Exclamation mark[12]
Danger
H225, H302, H312, H315, H319, H332[12]
P210, P280, P301+P312, P303+P361+P353, P304+P340+P312, P305+P351+P338[12]
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformFlammability 3: Liquids and solids that can be ignited under almost all ambient temperature conditions. Flash point between 23 and 38 °C (73 and 100 °F). E.g. gasolineInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
2
3
0
Flash point 20 °C (68 °F; 293 K)[16]
482 °C (900 °F; 755 K)[16]
Explosive limits 1.8–12.4%[3]
5 ppm (TWA)
Lethal dose or concentration (LD, LC):
891 mg/kg (rat, oral)
1500 mg/kg (mouse, oral)
1580 mg/kg (rat, oral)[14]
9000 ppm (rat, 1 hr)[14]
NIOSH (US health exposure limits):
PEL (Permissible)
 TWA 5 ppm (15 mg/m3)[3]
REL (Recommended)
 TWA 5 ppm (15 mg/m3)[3]
IDLH (Immediate danger)
 1000 ppm[3]
Related compounds
Related amines
 Picoline
Quinoline
Related compounds
 Aniline
Pyrimidine
Piperidine
Supplementary data page
Pyridine (data page)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
☒N verify (what is checkY☒N ?)

Pyridine is a basic heterocyclic organic compound with the chemical formula C5H5N. It is structurally related to benzene, with one methine group (=CH−) replaced by a nitrogen atom (=N−). It is a highly flammable, weakly alkaline, water-miscible liquid with a distinctive, unpleasant fish-like smell. Pyridine is colorless, but older or impure samples can appear yellow, due to the formation of extended, unsaturated polymeric chains, which show significant electrical conductivity.[page needed][17] The pyridine ring occurs in many important compounds, including agrochemicals, pharmaceuticals, and vitamins. Historically, pyridine was produced from coal tar. As of 2016, it is synthesized on the scale of about 20,000 tons per year worldwide.[2]

  1. ^ Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book). Cambridge: The Royal Society of Chemistry. 2014. p. 141. doi:10.1039/9781849733069-FP001. ISBN 978-0-85404-182-4.
  2. ^ a b Cite error: The named reference ul was invoked but never defined (see the help page).
  3. ^ a b c d e f NIOSH Pocket Guide to Chemical Hazards. "#0541". National Institute for Occupational Safety and Health (NIOSH).
  4. ^ a b c d e Haynes, p. 3.474
  5. ^ Haynes, p. 5.176
  6. ^ Haynes, p. 5.95
  7. ^ Haynes, p. 3.579
  8. ^ Haynes, p. 6.258
  9. ^ Haynes, p. 6.246
  10. ^ Haynes, p. 9.65
  11. ^ Haynes, pp. 5.34, 5.67
  12. ^ a b c Cite error: The named reference GESTIS was invoked but never defined (see the help page).
  13. ^ Pyridine: main hazards, precautions and toxicity
  14. ^ a b "Pyridine". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
  15. ^ "Pyridine MSDS". fishersci.com. Fisher. Archived from the original on 11 June 2010. Retrieved 2 February 2010.
  16. ^ a b Haynes, p. 15.19
  17. ^ Vaganova, Evgenia; Eliaz, Dror; Shimanovich, Ulyana; Leitus, Gregory; Aqad, Emad; Lokshin, Vladimir; Khodorkovsky, Vladimir (January 2021). "Light-Induced Reactions within Poly(4-vinyl pyridine)/Pyridine Gels: The 1,6-Polyazaacetylene Oligomers Formation". Molecules. 26 (22): 6925. doi:10.3390/molecules26226925. ISSN 1420-3049. PMC 8621047. PMID 34834017.