Pyridine is a basic, aromatic, heterocyclic, organic chemical compound that is structurally related to benzene, with one methine group (=CH-) replaced by a nitrogen atom.
Names and Identifiers
Name Pyridine
Formula C5H5N
Molar mass 79.102 (g/mol)
CAS registry number 110-86-1
EC number EINECS 203-809-9
InChI Key JUJWROOIHBZHMG-UHFFFAOYSA-N
Other names, synonyms Azabenzene; Azine; Azinine
Latin name Pyridinium
Chemical formulas
Molecular formula and structural formula of Pyridine:
C5H5N
Mr = 79.102 g/mol SMILES: C1=CC=NC=C1
Data and Properties
In its pure form, pyridine is a colorless, often light yellow, hygroscopic liquid that has an unpleasant fishy, nauseating odor and is corrosive to plastics, plastic coatings and rubber.
solubility: + Miscible with water, alcohol, acetone, ether, benzene, chloroform, fatty oils and many organic solvents. partition coefficient logPOW = 0.65.
melting point -41.6 °C
boiling point 115.2 °C
flash point 21 °C
ignition temperature 482 °C
density 0.98272 g cm-3 at 20 °C
pKa value pK1a = 5.23 at 25 °C
vapor pressure 20.5 hPa at 20 °C
viscosity 0.974 cP at 20 °C 0.879 cP at 25 °C
surface tension 40.8 dyn/cm at 0 °C 38.0 dyn/cm at 20 °C 26.4 dyn/cm at 100 °C
refractive index nD = 1.50920 at 20 °C
standard enthalpy of formation 100.2 kJ/mol at 25 °C [l] 140 kJ/mol [g]
standard entropie 177 J/(mol K) at 25 °C
enthalpy of vaporization 40.2 kJ/mol
melting enthalpy 8.28 kJ/mol
enthalpy of combustion -2.782 MJ/mol
entropie of combustion 35.8 J/(mol K)
heat capacity 132.72 J/(mol K)
thermal conductivity 0.166 W/(m · K)
critical points Tc = 346.85 °C pc = 67 bar Vc = 229 cm3/mol
triple point -41.67 °C
dipole moment 2.215 D
ionization energy 9.27 eV
permittivity ε0 = 12.3 at 25 °C (dielectric constant)
magnetism diamagnetisch
magnetic susceptibility χ -48.7 × 10-6 cm3 mol-1
crystal structure: Orthorhombic crystal system, space group Pna21 No. 33, lattice parameters a = 1752 pm, b = 897 pm and c = 1135 pm, Z = 16.
Mass-related elemental composition and isotope proportions of the compound Pyridine - C5H5N - calculated based on molecular mass.
Symbol Element ENumber x of atoms ExData of the element and isotopes *Percentages of isotopesPercentage of Ex in formula massC Carbon5 Ar = 12.011 u ΣAr = 60.055 u 12C: 12 u [98,94 %] 13C: 13.00335 u [1,06 %] 14C: 14.00324 u [<< 1 %] 12C: 75.1162 % 13C: 0.80476 % 14C: trace 75.9210 %H Hydrogen5 Ar = 1.008 u ΣAr = 5.04 u 1H: 1.00783 u [99,99 %] 2H: 2.0141 u [0,01 %] 3H: 3.01605 u [<< 1 %] 1H: 6.37088 % 2H: 0.00064 % 3H: trace 6.3715 %N Nitrogen1ΣAr = 14.007 u 14N: 14.00307 u [99,6205 %] 15N: 15.00011 u [0,3795 %] 14N: 17.64032 % 15N: 0.0672 % 17.7075 %
*) The third column lists the atomic masses or isotope masses of the elements involved and - in square brackets - the natural isotope composition.
More calculated data
The molar mass is M = 79.102 grams per mole.
The amount of substance in one kilogram of the substance is n = 12.642 mol.
The amount of substance in one gram of the substance is n = 0.013 mol.
Monoisotopic mass: 79.042199165251 Da - related to 12C51H514N.
Hazard warnings according to GHS
(General information without guarantee of accuracy and completeness! The information does not replace the chemical safety data sheet or a risk assessment, but rather provides a general overview of the risk posed by the hazardous substance.
Signal word: Danger
GHS hazard statements (H phrases):
H225 Highly flammable liquid and vapour
H302 Harmful if swallowed
H312 Harmful in contact with skin
H315 Causes skin irritation
H319 Causes serious eye irritation
H332 Harmful if inhaled
In a range of 1.7 to 12,4 vol%, pyridine forms explosive mixtures with air.
LD50 (rat, oral): 892 mg/kg.
Labeling in the EU: See ECHA Substance Infocard 100.003.464.
WHO IARC group 2B: Possibly carcinogenic to humans! See there under monograph 77, 119, (2019).
For toxicology and occupational safety when handling Pyridine as well as measures to be taken in case of danger, see: Hazardous Substances Information System GESTIS, ZVG-Nr. 013850.
International Chemical Safety Card ICSC (SDS, MSDS): See ICSC: 0323.
External Sources
PubChem:ID 1049ChemSpider:ID 1020Kegg database DBGET:ID C00747UNII of the FDA (USA):Unique Ingredient Identifier NH9L3PP67SEPA CompTox Chemicals Dashboard:DTXSID9021924Other CAS RN:152758-95-7; 163392-20-9; 45410-39-7; 62301-32-0; 6999-00-4; 82005-06-9; 85404-19-9; 85404-20-2; 733733-47-6; 857961-06-9 (also used, outdated or deleted registration numbers)
Manufacturers and Sources of Supply
Pyridine as a commercial product from internationally active suppliers and search for analogues see: ZINC000000895354.
The table below lists producers and suppliers of Pyridine as a commercial chemical for laboratories, research, industry and production with the corresponding contact details.
Literature Sources
[0] - Specialist and research articles in scientific journals via PubMed: Pyridine.
