Pyridine

Pyridine
Full structural formula of pyridine	Skeletal formula of pyridine, showing the numbering convention
Ball-and-stick diagram of pyridine	Space-filling model of pyridine
Names
	Preferred IUPAC name Pyridine
	Systematic IUPAC name Azabenzene
	Other names Azine; Azinine
Identifiers
CAS Number	110-86-1 ;
3D model (JSmol)	Interactive image;
ChEBI	CHEBI:16227 ;
ChEMBL	ChEMBL266158 ;
ChemSpider	1020 ;
ECHA InfoCard	100.003.464
EC Number	203-809-9;
KEGG	C00747 ;
PubChem CID	1049;
UNII	NH9L3PP67S ;
CompTox Dashboard (EPA)	DTXSID9021924 ;
	InChI InChI=1S/C5H5N/c1-2-4-6-5-3-1/h1-5H Key: JUJWROOIHBZHMG-UHFFFAOYSA-N ; InChI=1/C5H5N/c1-2-4-6-5-3-1/h1-5H Key: JUJWROOIHBZHMG-UHFFFAOYAY;
	SMILES c1ccncc1;
Properties
Chemical formula	C5H5N
Molar mass	79.102 g·mol−1
Appearance	Colorless liquid
Odor	Nauseating, fish-like
Density	0.9819 g/mL (20 °C)
Melting point	−41.63 °C (−42.93 °F; 231.52 K)
Boiling point	115.2 °C (239.4 °F; 388.3 K)
Solubility in water	Miscible
log P	0.65
Vapor pressure	16 mmHg (20 °C)
Acidity (pKa)	5.23 (pyridinium)
Conjugate acid	Pyridinium
Magnetic susceptibility (χ)	−48.7·10−6 cm3/mol
Thermal conductivity	0.166 W/(m·K)
Refractive index (nD)	1.5095 (20 °C)
Viscosity	0.879 cP (25 °C)
Dipole moment	2.215 D
Thermochemistry
Heat capacity (C)	132.7 J/(mol·K)
Std enthalpy of; formation (ΔfH⦵298)	100.2 kJ/mol
Std enthalpy of; combustion (ΔcH⦵298)	−2.782 MJ/mol
Hazards
	Occupational safety and health (OHS/OSH):
Main hazards	Low to moderate hazard
	GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H225, H302, H312, H315, H319, H332
Precautionary statements	P210, P280, P301+P312, P303+P361+P353, P304+P340+P312, P305+P351+P338
NFPA 704 (fire diamond)	2 3 0
Flash point	20 °C (68 °F; 293 K)
Autoignition; temperature	482 °C (900 °F; 755 K)
Explosive limits	1.8–12.4%
Threshold limit value (TLV)	5 ppm (TWA)
	Lethal dose or concentration (LD, LC):
LD50 (median dose)	891 mg/kg (rat, oral); 1500 mg/kg (mouse, oral); 1580 mg/kg (rat, oral)
LC50 (median concentration)	9000 ppm (rat, 1 hr)
	NIOSH (US health exposure limits):
PEL (Permissible)	TWA 5 ppm (15 mg/m3)
REL (Recommended)	TWA 5 ppm (15 mg/m3)
IDLH (Immediate danger)	1000 ppm
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). verify (what is ?) Infobox references

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. The pyridine ring occurs in many commercial 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.