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Acetonitrile

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Acetonitrile
Names
IUPAC name
Acetonitrile
Other names
methyl cyanide; cyanomethane; ethyl nitrile; ethanenitrile; methanecarbonitrile
Identifiers
3D model (JSmol)
ChEMBL
ChemSpider
ECHA InfoCard 100.000.760 Edit this at Wikidata
RTECS number
  • AL7700000
UNII
  • InChI=1S/C2H3N/c1-2-3/h1H3 checkY
    Key: WEVYAHXRMPXWCK-UHFFFAOYSA-N checkY
  • InChI=1/C2H3N/c1-2-3/h1H3
    Key: WEVYAHXRMPXWCK-UHFFFAOYAJ
  • N#CC
  • CC#N
Properties
C2H3N
Molar mass 41.053 g·mol−1
Appearance colorless liquid
Density 0.777 g/mL liquid
Melting point −45 °C
Boiling point 82 °C
miscible
Solubility organic solvents
Acidity (pKa) 25
Hazards
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformFlammability 3: Liquids and solids that can be ignited under almost all ambient temperature conditions. Flash point between 23 and 38 °C (73 and 100 °F). E.g. gasolineInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogen
2
3
0
Flash point 2 °C
Related compounds
Supplementary data page
Acetonitrile (data page)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
checkY verify (what is checkY☒N ?)

Acetonitrile is the chemical compound with formula CH3CN. This colourless liquid is the simplest organic nitrile. It is produced mainly as a byproduct of acrylonitrile manufacture. It is mainly used as a polar aprotic solvent in purification of butadiene.[2]

In the laboratory, it is used as a medium-polarity solvent that is miscible with water and has a convenient liquid range. With a dipole moment of 3.84 D, acetonitrile dissolves a wide range of ionic and nonpolar compounds and is useful as a mobile phase in HPLC and LCMS.

Applications

Acetonitrile is used mainly as a solvent in the purification of butadiene in refineries.

It is widely used in battery applications because of its relatively high dielectric constant and ability to dissolve electrolytes. For similar reasons it is a popular solvent in cyclic voltammetry. Its low viscosity and low chemical reactivity make it a popular choice for liquid chromatography. Acetonitrile plays a significant role as the dominant solvent used in the manufacture of DNA oligonucleotides from monomers. Industrially, it is used as a solvent for the manufacture of pharmaceuticals and photographic film.[3]

Organic synthesis

Acetonitrile is a common two-carbon building block in organic synthesis[4] of many useful chemicals, including acetophene, thiamine, acetamidine, and α-napthaleneacetic acid.[5] Its reaction with cyanogen chloride affords malononitrile.[2]

Ligand in coordination chemistry

In inorganic chemistry, acetonitrile is employed as a solvent and often an easily displaceable ligand. For example, PdCl2(CH3CN)2 is prepared by heating a suspension of (polymeric) palladium chloride in acetonitrile:

PdCl2 + 2 CH3CN → PdCl2(CH3CN)2

The CH3CN groups undergo rapid displacement by many other ligands.

Production

Acetonitrile is a by-product from the manufacture of acrylonitrile.[6] Production trends for acetonitrile thus generally follow those of acrylonitrile. Acetonitrile can also be produced by many other methods, but these are of no commercial importance as of 2002. Illustrative routes are by dehydration of acetamide or by hydrogenation of mixtures of carbon monoxide and ammonia.[7] The main distributors of acetonitrile in the world are: INEOS, Purification Technologies Inc, BioSolve BV, Carlo Erba Reagents, Panreac, J.T. Baker Chemical, VWR, Sigma Aldrich, and Petrolchem Trading Ltd. In 1992, 32.3 million pounds (14,700 t) of acetonitrile were produced in the US.

Acetonitrile shortage in 2008–2009

Starting in October 2008, the worldwide supply of acetonitrile was low because Chinese production was shut down for the Olympics. Furthermore, a U.S. factory was damaged in Texas during Hurricane Ike.[8] Owing to the global economic slowdown, the production of acrylonitrile that is used in acrylic fibers and acrylonitrile-butadiene-styrene (ABS) resins decreased. Because acetonitrile is a byproduct in the production of acrylonitrile, its production has also decreased.[9] The global shortage of acetonitrile continued through early 2009.

Safety

Toxicity

Acetonitrile has only a modest toxicity in small doses.[10][5] It can be metabolised to produce hydrogen cyanide, which is the source of the observed toxic effects.[3][11][12] Generally the onset of toxic effects is delayed, due to the time required for the body to metabolize acetonitrile to cyanide (generally about 2–12 hours).[5]

Cases of acetonitrile poisoning in humans (or, to be more specific, of cyanide poisoning after exposure to acetonitrile) are rare but not unknown, by inhalation, ingestion and (possibly) by skin absorption.[11] The symptoms, which do not usually appear for several hours after the exposure, include breathing difficulties, slow pulse rate, nausea, and vomiting: Convulsions and coma can occur in serious cases, followed by death from respiratory failure. The treatment is as for cyanide poisoning, with oxygen, sodium nitrite, and sodium thiosulfate among the most commonly-used remedies.[11]

It has been used in formulations for nail polish remover, despite its low but significant toxicity.[13] Acetone and ethyl acetate are often preferred as safer for domestic use, and acetonitrile has been banned in cosmetic products in the European Economic Area since March 2000.[14]

Metabolism and excretion

Compound Brain cyanide concentration (µg/kg) Oral LD50 (mg/kg)
Acetonitrile 28±5 2460
Propionitrile 508±84 40
Butyronitrile 437±106 50
Malononitrile 649±209 60
Acrylonitrile 395±106 90
Potassium cyanide 748±200 10
Ionic cyanide concentrations measured in the brains of Sprague-Dawley rats one hour after oral administration of an LD50 of various nitriles.[15]

In common with other nitriles, acetonitrile can be metabolised in microsomes, especially in the liver, to produce hydrogen cyanide, as was first shown by Pozzani et al. in 1959.[16] The first step in this pathway is the oxidation of acetonitrile to glyconitrile by an NADPH-dependent cytochrome P450 monooxygenase. The glyconitrile then undergoes a spontaneous decondensation to give hydrogen cyanide and formaldehyde.[10][11]

The metabolism of acetonitrile is much slower than that of other nitriles, which accounts for its relatively low toxicity. Hence, one hour after administration of a potentially lethal dose, the concentration of cyanide in the rat brain was one-twentieth that for a propionitrile dose 60 times lower (see table).[15]

The relatively slow metabolism of acetonitrile to hydrogen cyanide allows more of the cyanide produced to be detoxified within the body to thiocyanate (the rhodanese pathway). It also allows more of the acetonitrile to be excreted unchanged before it is metabolised. The main pathways of excretion are by exhalation and in the urine.[10][11][12]

References

  1. ^ http://www.sigmaaldrich.com/chemistry/solvents/acetonitrile-center.html
  2. ^ a b [1], Ashford's Dictionary of Industrial Chemicals, Third edition, 2011, page 76.
  3. ^ a b Spanish Ministry of Health (2002), Acetonitrile. Summary Risk Assessment Report (PDF), Ispra (VA), Italy: European Chemicals Bureau, Special Publication I.01.65
  4. ^ DiBiase, S. A.; Beadle, J. R.; Gokel, G. W. "Synthesis of α,β-Unsaturated Nitriles from Acetonitrile: Cyclohexylideneacetonitrile and Cinnamonitrile". Organic Syntheses{{cite journal}}: CS1 maint: multiple names: authors list (link); Collected Volumes, vol. 7, p. 108.
  5. ^ a b c Philip Wexler, ed. (2005), Encyclopedia of Toxicology, vol. Vol. 1 (2nd ed.), Elsevier, pp. 28–30, ISBN 0-12-745354-7 {{citation}}: |volume= has extra text (help)
  6. ^ Pollak, Peter; Romeder, G��Rard; Hagedorn, Ferdinand; Gelbke, Heinz-Peter (2000), Nitriles, doi:10.1002/14356007.a17_363. {{citation}}: replacement character in |first2= at position 2 (help)
  7. ^ US 4179462, Olive, G. & Olive, S., "Process for preparing acetonitrile", published 1979-12-18, assigned to Monsanto Company 
  8. ^ Lowe, Derek (2009), The Great Acetonitrile Shortage, Corante
  9. ^ Chemical & Engineering News, 86(47), p. 27 November 24, 2008
  10. ^ a b c Institut National de Recherche et de Sécurité (INRS) (2004), Fiche toxicologique nº 104 : Acétonitrile (PDF), Paris: INRS, ISBN 2-7389-1278-8
  11. ^ a b c d e International Programme on Chemical Safety (1993), Environmental Health Criteria 154. Acetonitrile, Geneva: World Health Organization
  12. ^ a b Greenberg, Mark (1999), Toxicological Review of Acetonitrile (PDF), Washington, D.C.: U.S. Environmental Protection Agency [dead link]
  13. ^ At least two cases have been reported of accidental poisoning of young children by acetonitrile-based nail polish remover, one of which was fatal: Caravati, EM (1988), "Pediatric cyanide intoxication and death from an acetonitrile-containing cosmetic", J. Am. Med. Assoc., 260 (23): 3470–73, doi:10.1001/jama.260.23.3470, PMID 3062198 {{citation}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  14. ^ Twenty-Fifth Commission Directive 2000/11/EC of 10 March 2000 adapting to technical progress Annex II to Council Directive 76/768/EEC on the approximation of laws of the Member States relating to cosmetic products. OJEC L65 of 2000-03-14, pp. 22–25.
  15. ^ a b Ahmed, AE (1982), "Comparative toxicities of aliphatic nitriles", Toxicol. Lett., 12 (2–3): 157–64, doi:10.1016/0378-4274(82)90179-5 {{citation}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  16. ^ Pozzani, UC (1959), "An investigation of the mammalian toxicity of acetonitrile", J. Occup. Med., 1 (12): 634–642, doi:10.1097/00043764-195912000-00003, PMID 14434606 {{citation}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)

External links

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