Acetonitrile

Acetonitrile, often abbreviated MeCN (methyl cyanide), is the chemical compound with the formula CH
3CN. This colourless liquid is the simplest organic nitrile (hydrogen cyanide is a simpler nitrile, but the cyanide anion is not classed as organic). It is produced mainly as a byproduct of acrylonitrile manufacture. It is used as a polar aprotic solvent in organic synthesis and in the purification of butadiene.[5] The N≡C−C skeleton is linear with a short C≡N distance of 1.16 Å.[6]

Not to be confused with Acetyl cyanide.
Acetonitrile
Skeletal formula of acetonitrile
Skeletal formula of acetonitrile with all explicit hydrogens added
Ball and stick model of acetonitrile
Spacefill model of acetonitrile
Names
Preferred IUPAC name
Acetonitrile[1]
Systematic IUPAC name
Ethanenitrile[1]
Other names
  • Cyanomethane[2]
  • Ethyl nitrile[2]
  • Methanecarbonitrile[2]
  • Methyl cyanide[2]
  • MeCN
Identifiers
3D model (JSmol)
741857
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.000.760
EC Number
  • 200-835-2
895
MeSH acetonitrile
RTECS number
  • AL7700000
UNII
UN number 1648
Properties
C2H3N
Molar mass 41.053 g·mol−1
Appearance Colorless liquid
Odor Faint, distinct, fruity
Density 0.786 g/cm3
Melting point −46 to −44 °C; −51 to −47 °F; 227 to 229 K
Boiling point 81.3 to 82.1 °C; 178.2 to 179.7 °F; 354.4 to 355.2 K
Miscible
log P −0.334
Vapor pressure 9.71 kPa (at 20.0 °C)
530 μmol/(Pa·kg)
Acidity (pKa) 25
Basicity (pKb) −11
UV-vis (λmax) 195 nm
Absorbance ≤0.10
−28.0×10−6 cm3/mol
1.344
Thermochemistry
91.69 J/(K·mol)
149.62 J/(K·mol)
Std enthalpy of
formation (ΔfH⦵298)
 40.16–40.96 kJ/mol
Std enthalpy of
combustion (ΔcH⦵298)
 −1256.03 – −1256.63 kJ/mol
Hazards
Safety data sheet See: data page
GHS pictograms
GHS Signal word Danger
GHS hazard statements
 H225, H302, H312, H319, H332
P210, P280, P305+351+338
NFPA 704 (fire diamond)
Flammability code 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. gasolineHealth code 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
3
2
0
Flash point 2.0 °C (35.6 °F; 275.1 K)
523.0 °C (973.4 °F; 796.1 K)
Explosive limits 4.4–16.0%
Lethal dose or concentration (LD, LC):
  • 2 g/kg (dermal, rabbit)
  • 2.46 g/kg (oral, rat)
5655 ppm (guinea pig, 4 hr)
2828 ppm (rabbit, 4 hr)
53,000 ppm (rat, 30 min)
7500 ppm (rat, 8 hr)
2693 ppm (mouse, 1 hr)[3]
16,000 ppm (dog, 4 hr)[3]
NIOSH (US health exposure limits):
PEL (Permissible)
 TWA 40 ppm (70 mg/m3)[4]
REL (Recommended)
 TWA 20 ppm (34 mg/m3)[4]
IDLH (Immediate danger)
 500 ppm[4]
Related compounds
Related alkanenitriles
Related compounds
 DBNPA
Supplementary data page
Refractive index (n),
Dielectric constant (εr), etc.
Thermodynamic
data
 Phase behaviour
solid–liquid–gas
UV, IR, NMR, MS
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Acetonitrile was first prepared in 1847 by the French chemist Jean-Baptiste Dumas.[7]

Applications

Acetonitrile is used mainly as a solvent in the purification of butadiene in refineries. Specifically, acetonitrile is fed into the top of a distillation column filled with hydrocarbons including butadiene, and as the acetonitrile falls down through the column, it absorbs the butadiene which is then sent from the bottom of the tower to a second separating tower. Heat is then employed in the separating tower to separate the butadiene.

In the laboratory, it is used as a medium-polarity solvent that is miscible with water and a range of organic solvents, but not saturated hydrocarbons. It has a convenient liquid range and a high dielectric constant of 38.8. With a dipole moment of 3.92 D,[8] acetonitrile dissolves a wide range of ionic and nonpolar compounds and is useful as a mobile phase in HPLC and LC–MS.

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 ultraviolet transparency UV cutoff, low viscosity and low chemical reactivity make it a popular choice for high-performance liquid chromatography (HPLC).

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.[9]

Organic synthesis

Acetonitrile is a common two-carbon building block in organic synthesis[10] of many useful chemicals, including acetamidine hydrochloride, thiamine, and α-napthaleneacetic acid.[11] Its reaction with cyanogen chloride affords malononitrile.[5]

Ligand in coordination chemistry

Acetonitrile is a ligand in many transition metal nitrile complexes. Being weakly basic, it is an easily displaceable ligand. For example, bis(acetonitrile)palladium dichloride is prepared by heating a suspension of palladium chloride in acetonitrile:[12]

PdCl
2 + 2 CH
3CN → PdCl
2(CH
3CN)
2

A related complex is [Cu(CH3CN)4]+. The CH
3CN groups in these complexes are rapidly displaced by many other ligands.

Production

Acetonitrile is a byproduct from the manufacture of acrylonitrile. Most is combusted to support the intended process but an estimated several thousand tons are retained for the above-mentioned applications.[13] 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.[14] In 1992, 14,700 tonnes (32,400,000 lb) of acetonitrile were produced in the US.

Catalytic ammoxidation of ethylene was also researched.[15]

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.[16] Due to the global economic slowdown, the production of acrylonitrile that is used in acrylic fibers and acrylonitrile butadiene styrene (ABS) resins decreased. Acetonitrile is a byproduct in the production of acrylonitrile and its production also decreased, further compounding the acetonitrile shortage.[17] The global shortage of acetonitrile continued through early 2009.

Safety

Toxicity

Acetonitrile has only modest toxicity in small doses.[11][18] It can be metabolised to produce hydrogen cyanide, which is the source of the observed toxic effects.[9][19][20] 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).[11]

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.[19] 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 emergency treatments.[19]

It has been used in formulations for nail polish remover, despite its toxicity. At least two cases have been reported of accidental poisoning of young children by acetonitrile-based nail polish remover, one of which was fatal.[21] 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.[22]

Metabolism and excretion
Compound Brain cyanide concentration (μg/kg) Oral LD50 (mg/kg)
Potassium cyanide 748 ± 200 10
Propionitrile 508 ± 84 40
Butyronitrile 437 ± 106 50
Malononitrile 649 ± 209 60
Acrylonitrile 395 ± 106 90
Acetonitrile 28 ± 5 2460
Table Salt n/a 3000
Ionic cyanide concentrations measured in the brains of Sprague-Dawley rats one hour after oral administration of an LD50 of various nitriles.[23]

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.[24] The first step in this pathway is the oxidation of acetonitrile to glycolonitrile by an NADPH-dependent cytochrome P450 monooxygenase. The glycolonitrile then undergoes a spontaneous decomposition to give hydrogen cyanide and formaldehyde.[18][19] Formaldehyde, a toxin and a carcinogen on its own, is further oxidized to formic acid, which is another source of toxicity.

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 ​1⁄20 that for a propionitrile dose 60 times lower (see table).[23]

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.[18][19][20]

Acetonitrile as an electron pair donor

Acetonitrile has a free electron pair at the nitrogen atom, which can form transition metal nitrile complexes with metals or lewis acid-base complexes with group 13 lewis acids like boron trifluoride[25]. In addition to BF3, acetonitrile forms 1:1 adducts with a variety of other Lewis acid such as I2, phenol, and trimethyltin chloride. It is classified are as a hard base and the ECW model lists its EB= 1.64 and CB= = 0.71. In superacids it is even possible to protonate acetonitrile.[26]

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See also

References
  1. Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book). Cambridge: The Royal Society of Chemistry. 2014. p. 902. doi:10.1039/9781849733069-FP001. ISBN 978-0-85404-182-4.
  2. "Material Safety Data Sheet" (PDF).
  3. "Acetonitrile". Immediately Dangerous to Life and Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
  4. NIOSH Pocket Guide to Chemical Hazards. "#0006". National Institute for Occupational Safety and Health (NIOSH).
  5. "Archived copy" (PDF). Ashford's Dictionary of Industrial Chemicals, Third edition. p. 76. Archived from the original (PDF) on 2011-05-16. Retrieved 2011-03-31.CS1 maint: archived copy as title (link)
  6. Karakida, Ken'ichi; Fukuyama, Tsutomu; Kuchitsu, Kozo (1974). "Molecular Structures of Hydrogen Cyanide and Acetonitrile as Studied by Gas Electron Diffraction". Bulletin of the Chemical Society of Japan. 47 (2): 299–304. doi:10.1246/bcsj.47.299.
  7. Dumas, J.-B. (1847). "Action de l'acide phosphorique anhydre sur les sels ammoniacaux" [Action of anhydrous phosphoric acid on ammonium salts]. Comptes rendus. 25: 383–384.
  8. Steiner, P. A.; Gordy, W. (1966). "Journal of Molecular Spectroscopy". 21: 291. Cite journal requires |journal= (help)
  9. Spanish Ministry of Health (2002), Acetonitrile. Summary Risk Assessment Report (PDF), Ispra (VA), Italy: European Chemicals Bureau, Special Publication I.01.65, archived from the original (PDF) on 2008-12-17
  10. DiBiase, S. A.; Beadle, J. R.; Gokel, G. W. "Synthesis of α,β-Unsaturated Nitriles from Acetonitrile: Cyclohexylideneacetonitrile and Cinnamonitrile". Organic Syntheses.; Collective Volume, 7, p. 108
  11. Philip Wexler, ed. (2005), Encyclopedia of Toxicology, Vol. 1 (2nd ed.), Elsevier, pp. 28–30, ISBN 0-12-745354-7
  12. Jürgen-Hinrich., Fuhrhop (2003). Organic synthesis : concepts and methods. Li, Guangtao, Dr. (3rd, completely rev. and enl. ed.). Weinheim: Wiley-VCH. p. 26. ISBN 9783527302727. OCLC 51068223.
  13. Pollak, Peter; Romeder, Gérard; Hagedorn, Ferdinand; Gelbke, Heinz-Peter. "Nitriles". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a17_363.
  14. US 4179462, Olive, G. & Olive, S., "Process for preparing acetonitrile", published 1979-12-18, assigned to Monsanto Company
  15. Rhimi, B.; Mhamdi, M.; Ghorbel, A.; Narayana Kalevaru, V.; Martin, A.; Perez-Cadenas, M.; Guerrero-Ruiz, A. (15 May 2016). "Ammoxidation of ethylene to acetonitrile over vanadium and molybdenum supported zeolite catalysts prepared by solid-state ion exchange". Journal of Molecular Catalysis A: Chemical. 416: 127–139. doi:10.1016/j.molcata.2016.02.028.
  16. Lowe, Derek (2009). "The Great Acetonitrile Shortage". Science Translational Medicine.
  17. A. Tullo (2008). "A Solvent Dries Up". Chemical & Engineering News. 86 (47): 27. doi:10.1021/cen-v086n047.p027.
  18. Institut national de recherche et de sécurité (INRS) (2004), Fiche toxicologique no. 104 : Acétonitrile (PDF), Paris: INRS, ISBN 2-7389-1278-8, archived from the original (PDF) on 2011-07-28, retrieved 2008-08-19
  19. International Programme on Chemical Safety (1993), Environmental Health Criteria 154. Acetonitrile, Geneva: World Health Organization
  20. Greenberg, Mark (1999), Toxicological Review of Acetonitrile (PDF), Washington, DC: U.S. Environmental Protection Agency
  21. Caravati, E. M.; Litovitz, T. (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.
  22. "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". Official Journal of the European Communities. L65: 22–25. 2000-03-14.
  23. Ahmed, A. E.; Farooqui, M. Y. H. (1982), "Comparative toxicities of aliphatic nitriles", Toxicol. Lett., 12 (2–3): 157–64, doi:10.1016/0378-4274(82)90179-5, PMID 6287676
  24. Pozzani, U. C.; Carpenter, C. P.; Palm, P. E.; Weil, C. S.; Nair, J. H. (1959), "An investigation of the mammalian toxicity of acetonitrile", J. Occup. Med., 1 (12): 634–642, doi:10.1097/00043764-195912000-00003, PMID 14434606
  25. B. Swanson, D. F. Shriver, J. A. Ibers, "Nature of the donor-acceptor bond in acetonitrile-boron trihalides. The structures of the boron trifluoride and boron trichloride complexes of acetonitrile", Inorg. Chem., 2969., volume 8, pp. 2182-2189, {{doi:10.1021/ic50080a032}}
  26. Template:Last1 = Haiges
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