Acetonitrile Formula

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Chemical Properties Of Acetonitrile

Chemical formulaC2H3N or CH3CN
Molecular weight41.053 g/mol
Chemical namesMethyl cyanide, Cyanomethane, Ethanenitrile
Density0.786 g/cm3
Boiling point81.3 to 82.1 °C
Melting point−46 to −44 °C
Solubility in waterMiscible

Acetonitrile is an organic chemical compound. It is the simplest organic nitrile. Mainly it is a byproduct in acrylonitrile manufacture. Also, we use it as a polar aprotic solvent in organic synthesis and in the purification of butadiene. The French chemist Jean-Baptiste Dumas firstly prepared it in 1847. Learn Acetonitrile Formula here.

Properties 0f Acetonitrile – C2H3N or CH3CN

  1. Molecular weight: 41.05 g/mol
  2. Density: 786 kg/m3
  3. Melting point: -46oC to -44oC
  4. Boiling point: 81.3oC to 82.1oC
  5. IUPAC ID: Acetonitrile
  6. Colour: Colorless
  7. Odor: Aromatic odor
  8. Taste: Sweetish taste
  9. Solubility: Soluble in water
  10. Chemical names: Methyl cyanide, Cyanomethane, Ethanenitrile

Acetonitrile formula and structure

The chemical formula of acetonitrile is CH3CN and its condensed formula is C2H3N. Furthermore, its molar mass is 41.05 g/mol. Scientists classify it as a nitrile (CN) in terms of its functional group. Besides, a nitrile is a carbon atom that contains a triple bond to a nitrogen atom.

A second carbon atom is a methyl group (-CH3) that bonds three hydrogen atoms. The central carbon atom has a triple bond to the nitrogen atom, the bond angle between the methyl group carbon, the central atom, and nitrogen atom is 180 degrees. The chemical structure of acetonitrile is:

Acetonitrile is an aliphatic nitrile and a volatile organic compound. Acetonitrile is less dense than water and its vapour is dense than air (Vapor pressure = 9.71 kPa). The structural formula of Acetonitrile is as shown below in the diagram.

Pictorial representation

Structural formula

Acetonitrile Occurrence

It is a byproduct that forms in the manufacturing of acrylonitrile. It is a derivative of acetic acid and is usually exists in aqueous solution.

Also, it is a secondary product in finding acrylonitrile from propylene ammoxidation or waste streams in the extraction process, chromatography, etc. Whereas we can also find other compounds like benzene, alcohol, and methanol.

Acetonitrile Preparation

Generally, the production trends for acetonitrile follow those of acrylonitrile. Other methods of preparation include the dehydration of acetamide or by hydrogenation of mixtures of carbon monoxide and ammonia. Besides, catalytic ammoxidation of ethylene also produces acetonitrile.

Preparation Of Acetonitrile – C2H3N or  CH3CN

By manufacturing acrylonitrile, it is obtained as a byproduct. It can also be synthesized by hydrogenation of mixtures of carbon monoxide or dehydration of acetamide and ammonia. A method was disclosed with the invention for preparing high purity Acetonitrile from acetic acid and ammonia by two steps which consist of the following two steps, 1. neutralizing acetic acid and ammonia to generate ammonium acetate, 2. Mixing aqueous solution of ammonium acetate and gaseous ammonia, preheating and making the mixture enter a fixed bed reactor which is filled with a catalyst aluminium oxide for reaction to generate acetonitrile which containing mixed gas, after continuously refining the gas we got pure Acetonitrile.

Acetonitrile physical properties

Its physical appearance is a colorless clear liquid with an aromatic odor. It is a weak base that has a density of 0.783 g/cm3. The melting point is between -46 to -44oC and the boiling point is 81.3 to 82.1oC. It is miscible in water.

Acetonitrile Chemical Properties

It is a nitrile (hydrogen cyanide) in which a methyl group replaces the hydrogen. Also, it a polar compound which means its atoms have the ability to attract electrons towards themselves. Moreover, the nitrogen atom is more electronegative than the carbon atom.

Acetonitrile Uses

Notably, it serves as a two-carbon building block in organic synthesis. Chemists use them as starting materials while constructing large and complex molecules. Also, it allows two carbon atoms and nitrogen atoms to be added. The most common use of acetonitrile is as a solvent for both reactions and compound purification applications.

Due to its polar nature, the compound allows it to successfully solvate a wide range of organic compounds. Besides, the high boiling point makes it best for conducting reactions at elevated temperatures. It is a highly flammable and liquid and vapor and has acute toxicity when coming in contact with skin. Also, it can cause serious eye damage and eye irritation.

Its common use in compound purification is an analytical chemistry application, especially in high-performance liquid chromatography (HPLC). In addition, it has been used in the formulation of nail polish remover. Moreover, industries use them to manufacture pharmaceuticals, rubber products, perfumes, pesticides, and batteries.

Safety and Health Hazards

Acetonitrile has modest toxicity in small doses. Also, it can be metabolized to form hydrogen cyanide that has toxic effects. The onset of toxic effects is delayed because generally, it requires time for the body to metabolize acetonitrile to cyanide. It can cause irritation in the eyes, throat, lungs, and nose.

Its long term effects include enlargement of the thyroid gland, headaches numbness, lack of appetite, dizziness, weakness, and tremor. Scientists observe reproductive problems in animals like increased birth defects, lower birth weight. Long term exposure to acetonitrile can affects the liver, lungs, central nervous system, and kidneys.

Toxicity
Acetonitrile has only modest toxicity in small doses. It can be metabolised to produce hydrogen cyanide, which is the source of the observed toxic effects. 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).

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. 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.

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. 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.

Applications Of Acetonitrile

  • Because of a high dielectric constant and capable to dissolve electrolytes acetonitriles are mainly used in battery applications.
  • It is used in high-performance liquid chromatography (HPLC).
  • It is used as a solvent in the manufacturing of DNA oligonucleotides, in a pharmaceutical field and in photographic film.

Uses Of Acetonitrile (C2H3N)

  1. In the extraction process of hydrocarbons, acetonitrile is used as a solvent.
  2. For the chemical reactions and in chromatography chemists use it as a solvent.
  3. To separate fatty acid from vegetable oil we use acetonitrile.
  4. Acetonitrile is used in making perfumes.
  5. In the production of synthetic pharmaceuticals, acetonitrile is widely used.
  6. Acetonitrile is used in the manufacturing of rubber.
  7. It is used in extraction of copper as well as refining.
  8. In electrochemical cells, it is used as a solvent.
  9. Because of its relatively high dielectric constant and ability to dissolve electrolytes, it is widely used in battery application.
  10.  Acetonitrile is being used in high-performance liquid chromatography (HPLC).
  11.  Acetonitrile has been used in formulations for nail polish remover
  12. In the manufacturing of DNA oligonucleotides, in a pharmaceutical field and in photographic film, acetonitrile is used as a solvent.

What Is Acetonitrile?

It is a chemical compound with the formula C2H3N or CH3CN and it is a volatile organic compound. Acetonitrile is also called Cyanomethane or Methane Carbonitrile. It’s IUPAC name is Acetonitrile. It is a nitrile which is a hydrogen cyanide where the hydrogen (H) is replaced by a methyl group (-CH3). Acetonitrile is a limpid liquid, which is totally colourless. It has an aromatic odor. Compared with water it is less dense than water. When compared with air, it’s vapours are denser. Acetonitrile is easily soluble in water and it has a sweetish taste. It is used as a medium-polarity solvent in the laboratory. Acetonitrile was first prepared by Jean Baptiste Dumas in the year of 1847. It is mainly produced as a byproduct of acrylonitrile manufacture.  In the European Economic Area since March 2000,  acetonitrile has been banned in cosmetic products. It is often preferred as safe for domestic use.

Organic synthesis

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

As an electron pair donor

Acetonitrile has a free electron pair at the nitrogen atom, which can form 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:

PdCl2 + 2 CH3CN → PdCl2(CH3CN)2

It also forms Lewis adducts with group 13 Lewis acids like boron trifluoride. In superacids, it is possible to protonate acetonitrile.

Solved Example For You

Question: State the method of preparing bis(acetonitrile)palladium dichloride?

Solution: We can prepare bis(acetonitrile)palladium dichloride by heating a suspension of palladium chloride in acetonitrile:

PdCl2 + 2CH3CN → PdCl2(CH3CN)2

Fun Facts

1. Acetonitrile is a liquid that is colorless.

2. In the group nitrile acetonitrile is the simplest molecule.

3. Acetonitrile is quite cheap because it is made when plastic is being made.

4. Acetonitrile must be handled with caution because it is an extremely dangerous product, it can cause severe health effects or death.  Since acetonitrile is flammable, it can hurt our eyes.

5. Symptoms of acetonitrile exposure look like cyanide exposure and it can include pink colouring of the skin, dilated pupils, headache, nausea, and vomiting, dizziness, weakness, stiffness of the lower jaw, anxiety, pain and tightness in the chest, rapid breathing and pulse, irregular heartbeat, shortness of breath, etc.

6. Despite its toxicity, it has been used in formulations for nail polish remover. By acetonitrile-based nail polish remover, at least two cases have been reported of accidental poisoning of young children, one of which was fatal.

7. In the European Economic Area since March 2000,  acetonitrile has been banned in cosmetic products. It is often preferred as safe for domestic use.

FAQs (Frequently Asked Questions)

1. How can exposure to acetonitrile affect our health?

Acetonitrile must be handled with caution because it is an extremely dangerous product, it can cause severe health effects or death.  Since acetonitrile is flammable, it can hurt our eyes. Symptoms of acetonitrile exposure look like cyanide exposure and it can include pink colouring of the skin, dilated pupils, headache, nausea, and vomiting, dizziness, weakness, stiffness of the lower jaw, anxiety, pain and tightness in the chest, rapid breathing and pulse, irregular heartbeat, shortness of breath, etc. Due to acetonitrile, the thyroid gland can be enlarged and can last for months or years.

2. What should be done if exposure to acetonitrile occurs?

The exposures and the steps we have to choose is:

  1. If there is eye contact with acetonitrile, the eyes should be flushed with large amounts of water and continue this process for several minutes, occasionally lifting the upper and lower lids. Remove contact lenses if possible.
  2. If there will be any skin contact with Acetonitrile, the skin should be immediately washed with soap and a large amount of water, and rinse thoroughly. Remove the contaminated clothes if a contact has been made with clothing. If necessary, cut the clothing off, and do not pull it over the head. Until it can be decontaminated or disposed of properly, leave it in a double bag closed container.
  3. To avoid breathing problems, leave the area of exposure immediately and move to an area of fresh air. 

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. 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. In 1992, 14,700 tonnes (32,400,000 lb) of acetonitrile were produced in the US.

Catalytic ammoxidation of ethylene was also researched.

Metabolism and excretion

Compound Cyanide, concentration in brain (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 (NaCl) 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.

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. 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. 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).

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.

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