Difference between revisions of "Pyridine"

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{{Chembox
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| Name = Pyridine
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| Reference =
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| IUPACName = Pyridine
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| PIN =
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| SystematicName =
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| OtherNames = Azabenzene<br>Azine
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| ImageFile1 = Pyridine bottle and sample.jpg
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| ImageSize1 = 250
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| ImageCaption1 = Pyridine sample and bottle.
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| ImageFile2 = Pyridine structure.png
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| Section1 = {{Chembox Identifiers
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| 3DMet =
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| Abbreviations =
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| SMILES = c1ccncc1
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  }}
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| Section2 = {{Chembox Properties
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| AtmosphericOHRateConstant =
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| Appearance = Colorless liquid
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| BoilingPt =
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| BoilingPtC = 115.2
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| BoilingPt_ref =
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| BoilingPt_notes =
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| Density = 0.9819 g/mL (at 20°C)
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| Formula = C<sub>5</sub>H<sub>5</sub>N
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| HenryConstant =
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| LogP =
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| MolarMass = 79.10 g/mol
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| MeltingPt =
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| MeltingPtC = −41.6
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| MeltingPt_notes =
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| Odor = Nauseating, rotten fish-like
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| pKa = 5.25 (for the conjugate acid)
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| pKb =
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| Solubility = Miscible
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| SolubleOther = Miscible with [[ethanol]], [[diethyl ether]], [[ethyl acetate]], [[Dimethyl sulfoxide|DMSO]], [[isopropanol]], [[methanol]], [[petroleum ether]]
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| VaporPressure = 16 mmHg (20°C)
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| Viscosity = 0.88 cP
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  }}
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| Section5 = {{Chembox Explosive
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| ShockSens = Non-explosive
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| FrictionSens = Non-explosive
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| DetonationV = Non-explosive
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| REFactor = Non-explosive
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  }}
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| Section6 = {{Chembox Hazards
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| AutoignitionPt =
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| ExploLimits = 1.8%–12.4%
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| ExternalMSDS = [http://www.sciencelab.com/msds.php?msdsId=9927409 ScienceLab]
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| FlashPt = 21 °C
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| LD50 = 891 mg/kg (rat, oral)<br>1500 mg/kg (mouse, oral)<br>1580 mg/kg (rat, oral)
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| LC50 = 9000 ppm (rat, 1 hr)
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| MainHazards = Toxic<br>Flammable
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| Section7 = {{Chembox Related
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| OtherAnions =
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| OtherCompounds = [[Aniline]]<br>[[Piperidine]]
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  }}
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}}
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'''Pyridine''', also known as '''azine''', is an organic compound consisting of a [[benzene]] ring with one =CH- group being replaced by a [[nitrogen]] atom, giving the chemical formula '''C<sub>5</sub>H<sub>5</sub>N'''.
 
'''Pyridine''', also known as '''azine''', is an organic compound consisting of a [[benzene]] ring with one =CH- group being replaced by a [[nitrogen]] atom, giving the chemical formula '''C<sub>5</sub>H<sub>5</sub>N'''.
  

Revision as of 22:59, 14 May 2016

Pyridine
Pyridine bottle and sample.jpg
Pyridine sample and bottle.
Pyridine structure.png
Names
IUPAC name
Pyridine
Other names
Azabenzene
Azine
Identifiers
Jmol-3D images Image
Properties
C5H5N
Molar mass 79.10 g/mol
Appearance Colorless liquid
Odor Nauseating, rotten fish-like
Density 0.9819 g/mL (at 20°C)
Melting point −41.6 °C (−42.9 °F; 231.6 K)
Boiling point 115.2 °C (239.4 °F; 388.3 K)
Miscible
Solubility Miscible with ethanol, diethyl ether, ethyl acetate, DMSO, isopropanol, methanol, petroleum ether
Vapor pressure 16 mmHg (20°C)
Acidity (pKa) 5.25 (for the conjugate acid)
Viscosity 0.88 cP
Hazards
Safety data sheet ScienceLab
Flash point 21 °C
Lethal dose or concentration (LD, LC):
891 mg/kg (rat, oral)
1500 mg/kg (mouse, oral)
1580 mg/kg (rat, oral)
9000 ppm (rat, 1 hr)
Related compounds
Related compounds
 Aniline
Piperidine
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Pyridine, also known as azine, is an organic compound consisting of a benzene ring with one =CH- group being replaced by a nitrogen atom, giving the chemical formula C5H5N.

Properties

Chemical

Pyridine is a weakly basic due to the lone pair on its nitrogen atom, and forms a stable hydrochloride salt when reacted with hydrochloric acid. It readily forms many coordination complexes with transition metal ions, as do its derivatives, 2,2'-bipyridine and terpyridine. Stronger Lewis bases can be subsituted for these ligands, making these complexes useful precursors.

Pyridine is a useful Lewis base in organic chemistry. It is a precursor to piperidine, another organic building block, which can be prepared by hydrogenation in the presence of a catalyst. In addition, pyridine can function as a polar solvent within which reactions can occur. Pyridinium chlorochromate, produced from pyridine and chromic and hydrochloric acids, can be used to oxidize primary alcohols to aldehydes and secondary alcohols to ketones.

Physical

Pyridine is a clear liquid at room temperature with a disagreeable "fishy" odor, described by some as "rotten fish". Pyridine has historically been added to ethanol to denature it, owing to its very bitter taste. It is miscible with water and polar solvents. It is also highly flammable, with a flash point of only 17 °C, but an autoignition temperature far outside the range of those commonly encountered.

Acquisition

Pyridine can be purchased, though not cheaply, from several online chemistry suppliers in nearly pure form.

Preparation

Pyridine can be prepared in one route useful to the home chemist by the catalytic decarboyxlation of niacin (nictotinic acid) at the boiling point of pyridine(115.2 °C) using copper chromite, in which pyridine vapor distills off and can be condensed. The copper chromite used is easily produced from copper ammonium chromate (produced from copper sulfate and an ammonium dichromate) through strong heating to cause decomposition. The same synthesis may be accomplished at temperatures in excess of 300°C using calcium oxide instead. It is also created by a catalyzed vapor phase reaction between ammonia, formaldehyde, and acetaldehyde.

Pyridine can also be derived by distillation from either coal tar or, historically, bone oil, a product of the destructive distillation of bones which contains several useful reagents if properly separated.

Projects

  • Piperidine synthesis
  • General solvent

Handling

Safety

Pyridine is toxic and possibly carcinogenic, causing a myriad of health issues if exposure is high. Because it is easily detectable by its strong unpleasant smell and unlikely to be consumed due to its very bitter taste, chances of serious or lethal exposure are low. Pyridine is also very flammable, with a flash point of only 17 degrees. As such, any reactions or use of pyridine should be done away from ignition sources and with proper fire safety equipment on hand.

It is often said that pyridine can cause instant male sterility on intake, but these claims are difficult to substantiate.

Storage

Pyridine should be stored in closed bottles away from any reagents, in a special chemical storage cabinet.

Disposal

Pyridine can be burned.

References

Relevant Sciencemadness threads

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