What Is Acetonitrile?
Table of Content
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.
Properties 0f Acetonitrile - C2H3N or CH3CN
Molecular weight: 41.05 g/mol
Density: 786 kg/m3
Melting point: -46oC to -44oC
Boiling point: 81.3oC to 82.1oC
IUPAC ID: Acetonitrile
Colour: Colorless
Odor: Aromatic odor
Taste: Sweetish taste
Solubility: Soluble in water
Chemical names: Methyl cyanide, Cyanomethane, Ethanenitrile
Structure Of Acetonitrile - C2H3N or CH3CN
Acetonitrile is classified as a nitrile in terms of its functional group. As per organic chemistry, a nitrile is defined as a carbon atom that contains a triple bond to a nitrogen atom. Acetonitrile is the simplest organic nitrile which contains a carbon nitrogen triple bond.
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.
Uses Of Acetonitrile (C2H3N)
In the extraction process of hydrocarbons, acetonitrile is used as a solvent.
For the chemical reactions and in chromatography chemists use it as a solvent.
To separate fatty acid from vegetable oil we use acetonitrile.
Acetonitrile is used in making perfumes.
In the production of synthetic pharmaceuticals, acetonitrile is widely used.
Acetonitrile is used in the manufacturing of rubber.
It is used in extraction of copper as well as refining.
In electrochemical cells, it is used as a solvent.
Because of its relatively high dielectric constant and ability to dissolve electrolytes, it is widely used in battery application.
Acetonitrile is being used in high-performance liquid chromatography (HPLC).
Acetonitrile has been used in formulations for nail polish remover
In the manufacturing of DNA oligonucleotides, in a pharmaceutical field and in photographic film, acetonitrile is used as a solvent.
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 on Acetonitrile
1. What is acetonitrile and what is its chemical formula?
Acetonitrile is an organic chemical compound and the simplest organic nitrile. Its chemical formula is CH₃CN. It is also known by its IUPAC name, ethanenitrile, as well as cyanomethane or methyl cyanide. Structurally, it consists of a methyl group (-CH₃) attached to a cyanide group (-CN).
2. What are the main physical properties of acetonitrile?
Acetonitrile exhibits several distinct physical properties relevant to its use in chemistry. These include:
- Appearance: It is a clear, colourless liquid.
- Odour: It has a faint, sweetish, aromatic odour.
- Solubility: It is miscible with water and many organic solvents.
- Boiling Point: Approximately 81-82°C.
- Density: It is less dense than water, with a density of about 786 kg/m³.
- State: It is a volatile liquid at room temperature.
3. What are the primary uses of acetonitrile in labs and industries?
Acetonitrile is a versatile solvent with numerous applications. Its primary uses include:
- As a medium-polarity solvent in chemical synthesis and reactions.
- As the mobile phase in analytical techniques, particularly High-Performance Liquid Chromatography (HPLC).
- In the manufacturing of pharmaceuticals, pesticides, and perfumes.
- For extracting fatty acids from oils.
- As a solvent in battery applications due to its ability to dissolve electrolytes.
- In the production of DNA oligonucleotides and rubber products.
4. Is acetonitrile considered a polar or nonpolar solvent?
Acetonitrile is classified as a polar aprotic solvent. Its polarity arises from the large dipole moment of the carbon-nitrogen triple bond (C≡N). However, unlike water or ethanol, it cannot donate hydrogen atoms to form hydrogen bonds, which is why it is called 'aprotic'. This unique combination allows it to dissolve a wide range of both polar and nonpolar substances.
5. How is acetonitrile commercially prepared?
The main commercial method for producing acetonitrile is as a byproduct during the manufacture of acrylonitrile, a monomer used to make acrylic plastics and fibres. It can also be synthesised through other methods, such as the dehydration of acetamide or by reacting acetic acid and ammonia over a catalyst like aluminium oxide.
6. Why is acetonitrile a preferred solvent for High-Performance Liquid Chromatography (HPLC)?
Acetonitrile is highly favoured in HPLC for several key reasons. Its low viscosity reduces the back pressure in HPLC systems, allowing for faster flow rates. It has a low UV cutoff, meaning it is transparent to UV light at low wavelengths, which prevents it from interfering with the detection of many analytes. Furthermore, its ability to mix with water and dissolve a broad spectrum of compounds makes it ideal for reversed-phase chromatography, the most common HPLC mode.
7. What makes acetonitrile a nitrile, and how does its C≡N bond influence its properties?
Acetonitrile is a nitrile because it contains the -C≡N functional group. This cyano group is central to its chemical character. The strong, highly polarised triple bond between carbon and nitrogen creates a significant dipole moment, making the molecule polar. The nitrogen atom's lone pair of electrons makes it a weak Lewis base. This structure is responsible for its utility as a polar aprotic solvent and allows it to undergo specific chemical reactions, such as hydrolysis to form carboxylic acids or reduction to form amines.
8. How does acetonitrile exert its toxic effects on the human body?
Acetonitrile is toxic, but its danger is primarily due to its metabolism within the body. After exposure, enzymes in the liver slowly metabolise acetonitrile into inorganic cyanide ions (CN⁻). This cyanide then inhibits cytochrome c oxidase, a critical enzyme in cellular respiration, effectively stopping cells from using oxygen. This delayed process is why symptoms of acetonitrile poisoning, which mimic cyanide poisoning (headache, dizziness, nausea), may not appear for several hours after exposure.
9. How does acetonitrile compare to other common lab solvents like acetone and water?
Acetonitrile has distinct advantages and differences compared to other solvents:
- Versus Water: Both are polar, but acetonitrile is aprotic (cannot donate hydrogen bonds) while water is protic. This makes acetonitrile a better choice for reactions where water might act as an unwanted acid or nucleophile.
- Versus Acetone: Both are polar aprotic solvents. However, acetonitrile is generally more stable, less reactive, and a weaker base than acetone. It is also more transparent at lower UV wavelengths, making it superior for analytical techniques like HPLC.
10. What is the chemical reasoning behind the first-aid measures for acetonitrile exposure?
The first-aid steps for acetonitrile exposure are based on its chemical properties. For skin or eye contact, flushing with large amounts of water is effective because acetonitrile is miscible with water, allowing it to be diluted and washed away quickly. For inhalation, moving to fresh air is critical to stop further absorption into the bloodstream via the lungs. Because of its delayed metabolism into cyanide, immediate medical attention is essential to administer specific antidotes that can counteract the effects of cyanide at a cellular level.
