Pyridine
Encyclopedia : P : PY : PYR : Pyridine
| Pyridine | |
|---|---|
| |
| General | |
| Systematic name | Pyridine |
| Other names | Azabenzene Azine |
| Molecular formula | C5H5N |
| SMILES | C1=NC=CC=C1 |
| Molar mass | 79.10 g/mol |
| Appearance | colourless liquid |
| CAS number | [110-86-1] |
| Properties | |
| Density and phase | 0.9819 g/cm3, liquid |
| Solubility in water | Miscible |
| Solubility in ethanol | Miscible |
| Melting point | −41.6 °C |
| Boiling point | 115.2 °C |
| Viscosity | 0.94 cP at 20 °C |
| Thermodynamic data | |
| Standard enthalpy of formation ΔfH°liquid | 101.2 kJ/mol |
| Standard enthalpy of combustion ΔcH°liquid | −2783.2 kJ/mol |
| Standard molar entropy S°liquid | ? J.K−1.mol−1 |
| Hazards | |
| EU classification | Flammable (F) Harmful (Xn) |
| NFPA 704 | |
| R-phrases | R11, R20, R21, R22 |
| S-phrases | S2, S26, S28 |
| Flash point | 20 °C |
| Supplementary data page | |
| Structure and properties | n, εr, etc. |
| Thermodynamic data | Phase behaviour Solid, liquid, gas |
| Spectral data | UV, IR, NMR, MS |
| Regulatory data | Flash point, RTECS number, etc. |
| Related compounds | |
| Related amines | Picoline Quinoline |
| Related compounds | Aniline Pyrimidine |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) [Chemical infoboxInfobox disclaimer and references] | |
Pyridine is a clear liquid with an odor that is sour, putrid, and fish-like. Pyridine is a simple heterocyclic aromatic organic compound that is structurally related to benzene, with one CH group in the six-membered ring replaced by a nitrogen atom. Pyridine is obtained from crude coal tar or is synthesized from acetaldehyde, formaldehyde and ammonia.
Pyridine has an equatorial lone pair of electrons at the nitrogen atom that does not participate in the aromatic pi-system. This makes pyridine a basic compound with chemical properties similar to tertiary amines with a pKa of the conjugate acid of 5.30. Pyridine is protonated by reaction with acids and forms a positively charged aromatic polyatomic ion called pyridinium cation. The bond lengths and bond angles in pyridine and the pyridinium ion do not differ greatly Tadeusz M. Krygowski, Halina Szatyowicz, and Joanna E. Zachara J. Org. Chem. 2005 70(22) 8859 - 8865; DOI: 10.1021/jo051354h [Abstract] because protonation does not involve the aromatic pi system.
Pyridine is also a good nucleophile with a donor number of 33.1.
Pyridine is widely used as a solvent and reagent in organic chemistry and it is also a starting material in the synthesis of compounds used as an intermediate in making insecticides, herbicides, pharmaceuticals, food flavorings, dyes, rubber chemicals, adhesives, paints, explosives and disinfectants. Pyridine is also used as a denaturant for antifreeze mixtures, for ethyl alcohol, and for fungicides, and as a dyeing aid for textiles.
Other examples of the pyridine class can be formed by the reaction of 1,5-diketones with ammonium acetate in acetic acid followed by oxidation.
Pyridine is a harmful substance if inhaled, ingested or absorbed through skin, it is known to reduce male fertility and is considered carcinogenic as well. Common symptoms of exposure to pyridine include: headache, coughing, asthmatic breathing, laryngitis, nausea and vomiting.
Related compounds
Structurally or chemically related compounds are- DMAP is short for 4-dimethylaminopyridine
- Bipyridine and viologen are simple polypyridine compounds consisting of two pyridine molecules joined by a single bond
- Terpyridine, a molecule of three pyridine rings connected together by two single bonds.
- Quinoline and Isoquinoline have pyridine and a benzene ring fused together.
- Aniline is a benzene derivative with an attached NH2 group and NOT a pyridine
- Diazines are compounds with one more carbon replaced by nitrogen such as Pyrazine and Pyramidine
- Triazines are compounds with two more carbons replaced by nitrogen
- 2,6-lutidine is a trivial name for 2,6-dimethylpyridine.
- collidine is a trivial name for 2,4,6-trimethylpyridine.
- Pyridinium p-toluenesulfonate (PPTS) is a salt formed by proton exchange between pyridine and p-toluenesulfonic acid
See also
- Hantzsch pyridine synthesis
- Simple aromatic rings
- 6-membered aromatic rings with one carbon replaced by another group: borabenzene, benzene, silabenzene, germanabenzene, stannabenzene, pyridine, phosphorine, pyrylium salt
References
External links
- For a full list of external links to MSDSs, spectroscopic data, commercial chemicals suppliers etc. for this compound, see [Chemical sources].
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