Pyridine

Heterocyclic aromatic organic compound / From Wikipedia, the free encyclopedia

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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
Pyridine_sample.jpg
Names
Preferred IUPAC name
Pyridine[1]
Systematic IUPAC name
Azabenzene
Other names
Azine
Azinine
1-Azacyclohexa-1,3,5-triene
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[12]
Occupational safety and health (OHS/OSH):
Main hazards
Low to moderate hazard[13]
GHS labelling:
GHS02: FlammableGHS07: Exclamation mark[14]
Danger
H225, H302, H312, H315, H319, H332[14]
P210, P280, P301+P312, P303+P361+P353, P304+P340+P312, P305+P351+P338[14]
NFPA 704 (fire diamond)
2
3
0
Flash point 20 °C (68 °F; 293 K)[15]
482 °C (900 °F; 755 K)[15]
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)[16]
9000 ppm (rat, 1 hr)[16]
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).
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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. 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.[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]