Acetonitrile (cyanomethane)

Acetonitrile, an aliphatic nitrile, is widely used as an organic solvent and intermediate in organic syntheses. As it is transparent to visible and UV light, it is used in spectrophotometric and fluorimetric techniques.

MeCN is used as a mobile phase component in many chromatographic techniques due to its low viscosity, high elution strength and unlimited water solubility.

It also plays an important role as the extraction medium in liquid-liquid extraction, solid-phase extraction or micro-extraction.

One of the main uses of Acetonitrile as a solvent is the purification of butadiene in refineries. MeCN fed to the top of a distillation column packed with hydrocarbons, including butadiene, as it descends through the column, absorbs the butadiene, which is then sent from the bottom of the column to a second separation column. Heat is then used in the separation tower to separate the butadiene.

In the laboratory, it is used as a medium polar solvent that can be freely mixed with water and a number of organic solvents, but not with saturated hydrocarbons. It has a comfortable liquid range and a high dielectric constant of 38.8. With a dipole moment of 3.92 D. Acetonitrile dissolves a wide range of ionic and non-polar compounds. It is irreplaceable as a mobile phase in HPLC and LC-MS.

It finds a wide range of applications in the production of batteries due to its relatively high dielectric constant and ability to dissolve electrolytes. For similar reasons, it is a popular solvent in cyclic voltammetry.

Acetonitrile plays a significant role as the dominant solvent used in the production of DNA oligonucleotides from monomers.

In industry, it is used as a solvent for the production of pharmaceuticals and photographic film.

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

Toxicity:

Acetonitrile has only minor toxicity in small doses. It can be metabolized to hydrogen cyanide, which is the source of the observed toxic effects. In general, the onset of toxic effects is delayed due to the time it takes for the body to convert acetonitrile to cyanide (usually around 2–12 hours).

Cases of acetonitrile poisoning in humans (or, more specifically, cyanide poisoning after exposure to acetonitrile) are rare, but not unknown, through inhalation, ingestion, and (possibly) through skin absorption.

Symptoms that usually don't appear for several hours after exposure include difficulty breathing, slow heart rate, nausea, and vomiting. In severe cases, convulsions and coma may occur, followed by death from respiratory failure. Treatment is as for cyanide poisoning, with oxygen, sodium nitrite, and sodium thiosulfate among the most common emergency treatments.

Despite its toxicity, it has been used in nail polish removers. At least two cases of accidental poisoning of young children with acetonitrile-based nail polish remover have been reported, one of which was fatal. Acetone and ethyl acetate are often preferred as safer for home use, and acetonitrile has been banned in cosmetic products in the European Economic Area since March 2000.

Like other nitriles, acetonitrile can be metabolized in microsomes, especially in the liver, to produce hydrogen cyanide, as first demonstrated by Pozzani et al. in 1959. The first step in this pathway is the oxidation of acetonitrile to glyconitrile by the NADPH-dependent cytochrome P450 monooxygenase. The glyconitrile then spontaneously decomposes to yield hydrogen cyanide and formaldehyde. Formaldehyde, itself a toxin and a carcinogen, 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 is the reason for its relatively low toxicity. Thus, one hour after administration of a potentially lethal dose, the concentration of cyanide in the rat's brain was 1⁄20 lower than that of a dose of propionitrile 60 times lower.

The relatively slow metabolism of acetonitrile to hydrogen cyanide allows more cyanide production in the body to be detoxified into thiocyanate (the rhodanese pathway). It also allows more acetonitrile to be excreted unchanged before it is metabolized. The main routes of excretion are exhalation and urine.

Properties:

Trade name: Acetonitrile

REACH number: 01-2119471307-38

EC number: 200-835-2

CAS number: 75-05-8

Chemical formula: CH3CN (molecular weight: 41.05)

Appearance/Form : clear, liquid

Colour: none transparent, colorless liquid

Odor: ether-like

Odor Threshold : No data available

pH : 6 - 10

Melting Point/Freezing Melting Point/Range: -48°C

Initial boiling point and boiling range: 81 - 82 °C

Flash point : 2.0 ° C - closed cup

Evaporation rate : 5.8

Upper explosion limit: 16% (V)

Lower explosion limit: 3% (V)

Vapor pressure:

73.18 hPa at 15 °C

121.44 hPa at 25 °C

413.23 hPa at 55 °C

98.64 hPa at 20°C

Vapor density: 1.42 - (air = 1.0)

Relative Density: 0.786g/ml at 25°C

Solubility in water: completely soluble

Explosive properties: Not explosive

Oxidizing properties: The substance or mixture is not classified as oxidizing.

Packaging:

Metal barrel 162.5 kg

Hazard statements:

• Highly flammable liquid and vapour.
• Harmful if swallowed.
• Harmful in contact with skin.
• Harmful if inhaled.
• Irritating to eyes.

Precautionary statements:

• Keep away from heat/sparks/open flames/hot surfaces. – Smoking
  prohibited.
• IF IN EYES: Rinse cautiously with water for several minutes. Remove
  contact lenses, if present and easy to remove. Continue rinsing.
• Store in a well-ventilated place.
• Store in a cool place.