Acetonitrile: Properties, Reactions, Uses Of Acetonitrile

Q: What are the health hazards caused by acetonitrile?

Health hazards caused by acetonitrile are: This compound is toxic if absorbed through the skin. It is highly flammable and releases toxic gases and vapours in the event of fire. A mixture of cyano methane and air or steam is explosive. If it comes into contact with strong oxidants, it may explode.

Acetonitrile: Properties, Reactions, Uses Of Acetonitrile

Edited By Team Careers360 | Updated on Jul 02, 2025 05:10 PM IST

Acetonitrile, often abbreviated as MeCN (methyl cyanide), is a compound with the formula CH3CN and the structure H3C—C≡N. This colourless liquid is the simplest organic nitrile, and even the simpler nitrile, but the cyanide anion is not classified as organic. It occurs mainly as a by-product in the production of acrylonitrile. Cyanomethane is a clear, colourless liquid with an aromatic odour. It has a flash point of 42°F and is less dense than water. The vapour is denser than air. Methane carbonitrile has a sweet taste and is readily soluble in water. It acts as a polar aprotic solvent and is an aliphatic nitrile.

This Story also Contains

Properties Of Acetonitrile
Reactions Of Acetonitrile
Uses Of Acetonitrile
Health Hazards Of Acetonitrile
Structure Of Acetonitrile
Manufacture Of Acetonitrile

Acetonitrile: Properties, Reactions, Uses Of Acetonitrile

Properties Of Acetonitrile

The molar mass of acetonitrile is 41.053 gmol-1.
It is a colourless liquid.
Has a faint, distinctive, fruity odour.
The density of acetonitrile is 0.786 g/cm3 at 25 °C.
The boiling point of acetonitrile is 81.3-82.1 °C, melting point of acetonitrile is -46 to -44 °C.
Miscible with water.
Acetonitrile has a vapour pressure of 9.71 kPa.
Acetonitrile has an acidity of 25.
The magnetic susceptibility of acetonitrile is -28.0×10−6 cm3/mol.
Its refractive index is 1.344.

Reactions Of Acetonitrile

1. Reaction with Concentrated Hydrochloric Acid

Partial hydrolysis of acetonitrile in cold concentrated hydrochloric acid forms the acetamide product. Upon complete hydrolysis, it forms a carboxylic acid.

2.Reaction with phenylmagnesium bromide

Nitrile reacts with a Grignard reagent to form a ketone. Nitriles i.e. RC≡N, react with Grignard or organolithium reagents to form ketones. Highly nucleophilic organometallic reagents add to C≡N bonds in a manner similar to aldehydes and ketones.

Uses Of Acetonitrile

Acetonitrile is used as a solvent for hydrocarbon extraction.
It is used for the separation of fatty acids from vegetable oils.
It is used in the manufacture of perfumes.
It is widely used in the manufacture of synthetic pharmaceuticals.
It is used in the manufacture of rubber.
Copper is refined and extracted using this process.
It is used as a solvent in electrochemical cells.
Chemists use it as a solvent in chemical reactions and chromatography.
It is widely used in battery applications due to its relatively high dielectric constant, and it also has the ability to dissolve electrolytes.
Acetonitrile is also used in high-performance liquid chromatography.
Acetonitrile was used in formulating a nail polish remover.
Acetonitrile is used in the manufacture of DNA oligonucleotides, in the pharmaceutical sector, and as a solvent in photographic films.

Health Hazards Of Acetonitrile

This compound is toxic if absorbed through the skin. It is highly flammable and releases toxic gases and vapours in the event of fire. A mixture of cyanomethane and air or steam is explosive. If it comes into contact with strong oxidants, it may explode. It can also explode when heated due to increased pressure. Severe exposure can cause a rash, delirium, numbness, irritation, confusion, and convulsions.

Structure Of Acetonitrile

Acetonitrile is classified as a nitrile based on its functional groups. According to organic chemistry, a nitrile is defined as a carbon atom containing a triple bond to a nitrogen atom. Acetonitrile is the simplest organic nitrile, containing a carbon-nitrogen triple bond.

Manufacture Of Acetonitrile

It is obtained as a by-product of the manufacture of acrylonitrile. It can also be synthesised by hydrogenating a mixture of carbon monoxide or dehydrating acetamide and ammonia. The present invention discloses a two-step process for producing high-purity acetonitrile from acetic acid and ammonia that consists of the following two steps: The first step is neutralising acetic acid and ammonia to form ammonium acetate. In the second step, this mixture was preheated and introduced into a fixed-bed reactor packed with an alumina catalyst to produce acetonitrile-containing mixed gas, and after continuous purification of this gas, pure acetonitrile was obtained.

Frequently Asked Questions (FAQs)

1. What is acetonitrile?

Acetonitrile, often abbreviated as MeCN (methyl cyanide), is a compound with the formula CH3CN and the structure H3C—C≡N. This colourless liquid is the simplest organic nitrile, and even the simpler nitrile, but the cyanide anion is not classified as organic. It occurs mainly as a by-product in the production of acrylonitrile. Cyanomethane is a clear, colourless liquid with an aromatic odor. It has a flash point of 42°F and is less dense than water.

2. What are the characteristics of acetonitrile?

The characteristics of acetonitrile are:

The molar mass of acetonitrile is 41.053 gmol-1.
It is a colourless liquid.
It has a faint, distinctive, fruity odor.
The density of acetonitrile is 0.786 g/cm3 at 25 °C.
The boiling point of acetonitrile is 81.3–82.1 °C, and the melting point of acetonitrile is -46 to -44 °C.
It is miscible with water.

3. What are the uses of acetonitrile?

The uses of acetonitrile are:

Acetonitrile is used as a solvent for hydrocarbon extraction.
It is used for the separation of fatty acids from vegetable oils.
It is used in the manufacture of perfumes.
It is widely used in the manufacture of synthetic pharmaceuticals.

4. How is acetonitrile made?

It is prepared in the following way:

It is obtained as a by-product of the manufacture of acrylonitrile. It can also be synthesised by hydrogenating a mixture of carbon monoxide or dehydrating acetamide and ammonia. The present invention discloses a two-step process for producing high-purity acetonitrile from acetic acid and ammonia, which consists of the following two steps: - The first step is neutralising acetic acid and ammonia to form ammonium acetate. In the second step, this mixture was preheated and introduced into a fixed-bed reactor packed with an alumina catalyst to produce acetonitrile-containing mixed gas, and after continuous purification of this gas, pure acetonitrile was obtained.

5. What are the health hazards caused by acetonitrile?

Health hazards caused by acetonitrile are:

6. What safety precautions should be taken when handling acetonitrile?

When handling acetonitrile, several safety precautions are necessary:

7. What is the environmental impact of acetonitrile usage?

The environmental impact of acetonitrile usage is a concern due to its potential toxicity and persistence. While it is not considered highly toxic, prolonged exposure can be harmful. Acetonitrile can contribute to air pollution and has the potential to contaminate water sources. However, it is biodegradable and does not bioaccumulate significantly. Proper handling, disposal, and recycling practices are essential to minimize its environmental impact in industrial and laboratory settings.

8. How does acetonitrile's freezing point depression property affect its use in chemical processes?

Acetonitrile's freezing point depression property is significant in several ways:

9. How does acetonitrile's ability to form azeotropes affect its purification and use?

Acetonitrile's ability to form azeotropes significantly affects its purification and use:

10. Why is acetonitrile considered a polar aprotic solvent?

Acetonitrile is considered a polar aprotic solvent because it has a high dipole moment (3.92 D) due to the cyano group, making it polar. However, it lacks hydrogen atoms bonded to electronegative elements like oxygen or nitrogen, so it cannot donate hydrogen bonds. This combination of polarity and inability to donate hydrogen bonds makes it an excellent solvent for many organic and inorganic compounds.

11. What is the significance of acetonitrile's dipole moment?

Acetonitrile's high dipole moment (3.92 D) is significant because it determines many of its solvent properties. The strong dipole allows acetonitrile to dissolve a wide range of polar and ionic compounds, making it useful in various chemical processes. It also contributes to acetonitrile's ability to participate in dipole-dipole interactions with other molecules, influencing its behavior in solution and as a reaction medium.

12. How does acetonitrile compare to water in terms of polarity?

Acetonitrile is less polar than water but more polar than many organic solvents. Water has a dipole moment of 1.85 D and can form hydrogen bonds, making it highly polar. Acetonitrile, with a dipole moment of 3.92 D, is polar due to its cyano group but cannot form hydrogen bonds. This intermediate polarity allows acetonitrile to dissolve both polar and non-polar compounds, making it a versatile solvent in chemistry.

13. How does acetonitrile's boiling point compare to similar organic compounds?

Acetonitrile has a relatively high boiling point (82°C) compared to similar-sized organic compounds. This is due to the strong dipole-dipole interactions between acetonitrile molecules, caused by the polar cyano group. For comparison, ethane (C₂H₆), which has a similar molecular weight but is non-polar, has a much lower boiling point of -89°C. This difference illustrates the significant effect of molecular polarity on boiling point.

14. How does the presence of water affect acetonitrile's properties as a solvent?

The presence of water significantly affects acetonitrile's properties as a solvent:

15. How does acetonitrile participate in nucleophilic addition reactions?

Acetonitrile can participate in nucleophilic addition reactions through its cyano group. The carbon atom in the cyano group is electrophilic due to the electron-withdrawing effect of the nitrogen. Nucleophiles can attack this carbon, forming an intermediate that can be hydrolyzed to produce various products. This reactivity is the basis for many synthetic applications of acetonitrile in organic chemistry.

16. How does acetonitrile react with Grignard reagents?

Acetonitrile reacts with Grignard reagents in a nucleophilic addition reaction. The Grignard reagent (RMgX) acts as a nucleophile, attacking the electrophilic carbon of the cyano group. This forms an imine intermediate, which upon hydrolysis yields a ketone. The overall reaction converts the nitrile (CN) group to a ketone (C=O) group, increasing the carbon chain length by one. This reaction is useful in organic synthesis for carbon-carbon bond formation.

17. What is the mechanism of acetonitrile's hydrolysis?

The hydrolysis of acetonitrile occurs through the following mechanism:

18. How does acetonitrile participate in the Ritter reaction?

In the Ritter reaction, acetonitrile acts as both a solvent and a reactant:

19. What is the role of acetonitrile in the synthesis of acrylic polymers?

Acetonitrile plays several important roles in the synthesis of acrylic polymers:

20. What is acetonitrile and what is its molecular formula?

Acetonitrile is an organic compound with the molecular formula CH₃CN. It is the simplest organic nitrile, consisting of a methyl group (CH₃) bonded to a cyano group (CN). Acetonitrile is a colorless liquid at room temperature and is commonly used as a solvent in various chemical processes.

21. How does the structure of acetonitrile contribute to its physical properties?

The structure of acetonitrile, with its methyl group and cyano group, contributes to its physical properties in several ways. The cyano group's strong polarity leads to a high boiling point (82°C) for its size. The molecule's small size and lack of hydrogen bond donors result in a low viscosity and high mobility. These properties make acetonitrile an excellent solvent for many applications.

22. What is the hybridization of the carbon atoms in acetonitrile?

In acetonitrile (CH₃CN), the carbon atoms have different hybridizations. The carbon in the methyl group (CH₃) is sp³ hybridized, with tetrahedral geometry. The carbon in the cyano group (CN) is sp hybridized, resulting in a linear geometry around this carbon atom. This difference in hybridization contributes to the overall structure and properties of the molecule.

23. How does acetonitrile's structure contribute to its use as a mobile phase in reversed-phase HPLC?

Acetonitrile's structure makes it an excellent mobile phase for reversed-phase HPLC due to several factors:

24. What is the significance of acetonitrile's dipole moment in spectroscopic applications?

Acetonitrile's high dipole moment (3.92 D) is significant in spectroscopy for several reasons:

25. What is the importance of acetonitrile in high-performance liquid chromatography (HPLC)?

Acetonitrile is widely used as a mobile phase in high-performance liquid chromatography (HPLC) due to several advantageous properties. Its low viscosity allows for better flow rates and lower backpressure. Its UV cutoff at 190 nm enables detection of a wide range of compounds. Acetonitrile's ability to dissolve both polar and non-polar substances makes it suitable for separating diverse analytes. Its low boiling point also facilitates easy removal during sample preparation.

26. What is the role of acetonitrile in the production of pharmaceuticals?

Acetonitrile plays a crucial role in pharmaceutical production. It is used as a solvent in the synthesis of various drug compounds due to its ability to dissolve a wide range of organic molecules. In drug purification, acetonitrile is employed in chromatographic techniques, particularly HPLC, to separate and analyze pharmaceutical compounds. Its low boiling point also makes it easy to remove from final products, ensuring purity in drug formulations.

27. What is the role of acetonitrile in the synthesis of heterocyclic compounds?

Acetonitrile plays several important roles in the synthesis of heterocyclic compounds:

28. How does acetonitrile behave as a ligand in coordination chemistry?

Acetonitrile can act as a ligand in coordination chemistry due to its ability to donate a lone pair of electrons from the nitrogen atom in the cyano group. It typically acts as a monodentate ligand, coordinating to metal centers through the nitrogen. This behavior makes acetonitrile useful in organometallic chemistry and in the synthesis of various metal complexes.

29. What is the significance of acetonitrile's dielectric constant?

Acetonitrile's dielectric constant (ε = 37.5 at 20°C) is significant for several reasons:

30. How does acetonitrile's structure influence its behavior in gas chromatography?

Acetonitrile's structure influences its behavior in gas chromatography (GC) in several ways: