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| Names | |||
|---|---|---|---|
| Preferred IUPAC name Acetonitrile[2] | |||
| Systematic IUPAC name Ethanenitrile[2] | |||
| Other names | |||
| Identifiers | |||
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3D model (JSmol) | |||
| 741857 | |||
| ChEBI | |||
| ChEMBL | |||
| ChemSpider |
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| ECHA InfoCard | 100.000.760 | ||
| EC Number |
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| 895 | |||
| MeSH | acetonitrile | ||
| RTECS number |
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| UNII | |||
| UN number | 1648 | ||
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| Properties | |||
| C2H3N | |||
| Molar mass | 41.053 g·mol−1 | ||
| Appearance | Colorless liquid | ||
| Odor | Faint, distinct, fruity | ||
| Density | 0.786 g/cm3 at 25°C | ||
| 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 | |||
| logP | −0.334 | ||
| Vapor pressure | 9.71 kPa (at 20.0 °C) | ||
Henry's law constant (kH) | 530 μmol/(Pa·kg) | ||
| Acidity (pKa) | 25 | ||
| UV-vis (λmax) | 195 nm | ||
| Absorbance | ≤0.10 | ||
| −28.0×10−6 cm3/mol | |||
Refractive index (nD) | 1.344 | ||
| 3.92 D | |||
| Thermochemistry | |||
| 91.69 J/(K·mol) | |||
Std molar entropy(S⦵298) | 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 | |||
| GHS labelling: | |||
  | |||
| Danger | |||
| H225,H302,H312,H319,H332 | |||
| P210,P280,P305+P351+P338 | |||
| NFPA 704 (fire diamond) | |||
| 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): | |||
LD50 (median dose) |
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LC50 (median concentration) | 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)[4] | ||
LCLo (lowest published) | 16,000 ppm (dog, 4 hr)[4] | ||
| NIOSH (US health exposure limits): | |||
PEL (Permissible) | TWA 40 ppm (70 mg/m3)[3] | ||
REL (Recommended) | TWA 20 ppm (34 mg/m3)[3] | ||
IDLH (Immediate danger) | 500 ppm[3] | ||
| Related compounds | |||
Related alkanenitriles | |||
Related compounds | DBNPA | ||
| Supplementary data page | |||
| Acetonitrile (data page) | |||
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |||
Acetonitrile, often abbreviatedMeCN (methyl cyanide), is thechemical compound with theformulaCH3CN andstructureH3C−C≡N. This colourless liquid is the simplest organicnitrile (hydrogen cyanide is a simpler nitrile, but thecyanide anion is not classed asorganic). It is produced mainly as a byproduct ofacrylonitrile manufacture. It is used as apolar aprotic solvent inorganic synthesis and in the purification ofbutadiene.[5] TheN≡C−C skeleton islinear with a shortC≡Ndistance of 1.16 Å.[6]
Acetonitrile was first prepared in 1847 by the French chemistJean-Baptiste Dumas.[7]
Acetonitrile is used mainly as a solvent in the purification ofbutadiene in refineries. Specifically, acetonitrile is fed into the top of adistillation column filled withhydrocarbons 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-polaritynon-protic solvent that ismiscible with water and a range of organic solvents, but not saturated hydrocarbons. It has a convenient range of temperatures at which it is a liquid, and a highdielectric constant of 38.8. With adipole moment of 3.92 D,[8] acetonitrile dissolves a wide range of ionic and nonpolar compounds and is useful as a mobile phase inHPLC andLC–MS.
It is widely used inbattery applications because of its relatively high dielectric constant and ability to dissolveelectrolytes. For similar reasons, it is a popular solvent incyclic voltammetry.
Its ultraviolet transparencyUV cutoff, lowviscosity and lowchemical reactivity make it a popular choice forhigh-performance liquid chromatography (HPLC).
Acetonitrile plays a significant role as the dominant solvent used inoligonucleotide synthesis fromnucleoside phosphoramidites.
Industrially, it is used as a solvent for the manufacture ofpharmaceuticals andphotographic film.[9]
Acetonitrile is a common two-carbon building block inorganic synthesis[10] of many useful chemicals, includingacetamidine hydrochloride,thiamine, and1-naphthaleneacetic acid.[11] Its reaction withcyanogen chloride affordsmalononitrile.[5]
Acetonitrile has a free electron pair at the nitrogen atom, which can form manytransition metal nitrile complexes. Being weakly basic, it is an easily displaceableligand. For example,bis(acetonitrile)palladium dichloride is prepared by heating a suspension ofpalladium chloride in acetonitrile:[12]
A related complex istetrakis(acetonitrile)copper(I) hexafluorophosphate[Cu(CH3CN)4]+. TheCH3CN groups in these complexes are rapidly displaced by many other ligands.
It also forms Lewis adducts with group 13Lewis acids likeboron trifluoride.[13] Insuperacids, it is possible to protonate acetonitrile.[14]
Acetonitrile is a byproduct from the manufacture ofacrylonitrile by catalyticammoxidation ofpropylene. Most is combusted to support the intended process but an estimated several thousand tons are retained for the above-mentioned applications.[15] Production trends for acetonitrile thus generally follow those ofacrylonitrile. Acetonitrile can also be produced by many other methods, but these are of no commercial importance as of 2002. Illustrative routes are by dehydration ofacetamide or byhydrogenation of mixtures ofcarbon monoxide andammonia.[16] In 1992[update], 14,700 tonnes (16,200 short tons) of acetonitrile were produced in the US.
Starting in October 2008, the worldwide supply of acetonitrile was low because Chinese production was shut down for theOlympics. Furthermore, a U.S. factory was damaged in Texas duringHurricane Ike.[17] Due to the global economic slowdown, the production of acrylonitrile used in acrylic fibers andacrylonitrile butadiene styrene (ABS) resins decreased. Acetonitrile is a byproduct in the production ofacrylonitrile and its production also decreased, further compounding the acetonitrile shortage.[18] The global shortage of acetonitrile continued through early 2009.[needs update]
Acetonitrile has only modest toxicity in small doses.[11][19] It can bemetabolised to producehydrogen cyanide, which is the source of the observed toxic effects.[9][20][21] 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.[20] The symptoms, which do not usually appear for several hours after the exposure, include breathing difficulties, slowpulse rate,nausea, and vomiting.Convulsions andcoma can occur in serious cases, followed by death fromrespiratory failure. The treatment is as forcyanide poisoning, withoxygen,sodium nitrite, andsodium thiosulfate among the most commonly used emergency treatments.[20]
It has been used in formulations fornail 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.[22]Acetone andethyl acetate are often preferred as safer for domestic use, and acetonitrile has been banned in cosmetic products in theEuropean Economic Area since March 2000.[23]
| Compound | Cyanide, concentration in brain (μg/kg) | OralLD50 (mg/kg) |
|---|---|---|
| Potassium cyanide | 700 ± 200 | 10 |
| Propionitrile | 510 ± 80 | 40 |
| Butyronitrile | 400 ± 100 | 50 |
| Malononitrile | 600 ± 200 | 60 |
| Acrylonitrile | 400 ± 100 | 90 |
| Acetonitrile | 28 ± 5 | 2460 |
| Table salt (NaCl) | — | 3000 |
| Ionic cyanide concentrations measured in the brains of Sprague-Dawley rats one hour after oral administration of anLD50 of various nitriles.[24] | ||
In common with othernitriles, acetonitrile can bemetabolised inmicrosomes, especially in the liver, to producehydrogen cyanide, as was first shown by Pozzaniet al. in 1959.[25] The first step in this pathway is the oxidation of acetonitrile toglycolonitrile by anNADPH-dependentcytochrome P450monooxygenase. The glycolonitrile then undergoes a spontaneous decomposition to give hydrogen cyanide andformaldehyde.[19][20] Formaldehyde, a toxin and a carcinogen on its own, is further oxidized toformic 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 was1⁄20 that for apropionitrile dose 60 times lower (see table).[24]
The relatively slow metabolism of acetonitrile to hydrogen cyanide allows more of the cyanide produced to be detoxified within the body tothiocyanate (therhodanese 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.[19][20][21]
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