Acetonitrile, Cyanomethane, Methyl Cyanide, Ethanonitrile, 75-05-8 

ACETONITRILE

Acetonitrile / Cyanomethane / Methyl Cyanide / Acetonitrile Gradient / R5
CAS Number: 75-05-8
EC Number: 200-835-2

1. PRODUCT IDENTIFICATION AND CHEMICAL IDENTITY

Acetonitrile is an important organic solvent belonging to the nitrile class, containing a nitrile group (-C≡N). It is a colorless, clear liquid with a sweet, ether-like characteristic odor. Due to its high dielectric constant and wide solubility range, it is one of the most widely used polar aprotic solvents in laboratory and industrial applications. It is completely miscible with water, alcohols, ether, acetone, chloroform, and many organic solvents, but immiscible with saturated hydrocarbons. It also has the ability to dissolve some inorganic salts such as silver nitrate, lithium nitrate, and magnesium bromide. Acetonitrile is produced industrially primarily as a byproduct of acrylonitrile production, as well as through acetic acid ammonolysis or acetylene ammonolysis. Major applications include high-performance liquid chromatography (HPLC) solvent, pharmaceutical intermediate, rubber monomer, organic synthesis solvent, and battery electrolytes. This highly flammable liquid has a very low flash point of 2°C, and its vapor can form explosive mixtures with air.

2. PHYSICAL AND CHEMICAL PROPERTIES

Acetonitrile is a colorless, clear liquid at room temperature with a sweet, ether-like odor. It has a density of 0.7857 g/cm³, making it lighter than water. The melting point is -46°C, and the boiling point is 81-82°C, making it a moderately volatile organic solvent. The flash point is extremely low at 2°C, classifying it as a highly flammable liquid. The vapor pressure at 20°C is 72.8 mm Hg, indicating high volatility. The vapor density is 1.41 (air=1), meaning its vapor is heavier than air and may accumulate in low-lying areas. Acetonitrile is completely miscible with water, diethyl ether, methanol, acetone, chloroform, carbon tetrachloride, vinyl chloride, methyl acetate, ethyl acetate, and many unsaturated hydrocarbons, but immiscible with saturated hydrocarbons. It can also dissolve some inorganic salts such as silver nitrate, lithium nitrate, and magnesium bromide. It forms an azeotrope with water at 16% water content with an azeotropic point of 76°C. The dielectric constant of 36.6 makes it a polar solvent with the ability to dissolve ionic compounds. Its low viscosity (0.35 cP) and high dipole moment (3.92 D) make acetonitrile an ideal solvent for chromatographic and electrochemical applications.

3. CHEMICAL PROPERTIES AND REACTIONS

Acetonitrile is an organic compound containing a nitrile group (-C≡N). The nitrile group provides the ability to undergo various chemical reactions.

Hydrolysis:

Acetonitrile undergoes hydrolysis under acidic or basic conditions to form acetic acid or acetamide:

CH₃CN + H₂O → CH₃CONH₂ (acetamide, with acid or base catalysis)

CH₃CN + 2 H₂O → CH₃COOH + NH₃ (acetic acid, under strong acidic hydrolysis)

Reduction:

Acetonitrile can be reduced to form ethylamine:

CH₃CN + 2 H₂ → CH₃CH₂NH₂ (catalytic hydrogenation)

Alkylation:

Acetonitrile reacts with strong bases (e.g., sodium amide, lithium diisopropylamide) to form nitrile anions, which can react with alkyl halides to form alkylated nitrile derivatives:

CH₃CN + NaNH₂ → CH₂CN⁻Na⁺ + NH₃

CH₂CN⁻Na⁺ + R-X → R-CH₂CN + NaX

Condensation (Friedel-Crafts Type):

In the presence of Lewis acids, acetonitrile reacts with aromatic compounds to form acetophenone derivatives (Houben-Hoesch reaction):

ArH + CH₃CN → Ar-CO-CH₃ (acetophenone derivative)

Polymerization:

Acetonitrile can polymerize in the presence of basic catalysts or high temperatures to form a black, solid polymer.

Thermal Decomposition:

At high temperatures, acetonitrile decomposes to cyanide compounds and hydrogen cyanide (HCN):

CH₃CN → HCN + CH₂ (thermal decomposition)

4. PRODUCTION METHODS

Acetonitrile is produced industrially primarily by three methods: acetic acid ammonolysis, acetylene ammonolysis, and as a byproduct of propylene ammoxidation.

Detailed Production Process (Acetic Acid Ammonolysis - Most Common):

1. Raw Material Feed: Acetic acid and ammonia are fed into a reactor containing an alumina (Al₂O₃) catalyst.

2. Reaction: The reaction is carried out at 360-420°C:

CH₃COOH + NH₃ → CH₃CN + 2 H₂O

3. Absorption: The reaction products (acetonitrile, water, unreacted raw materials) are absorbed in water.

4. Distillation: The absorbed mixture is purified by distillation. Acetonitrile is collected at its boiling point of 81-82°C.

5. Purification: Additional distillation or drying steps are applied depending on the required purity. HPLC grade requires special purification processes.

Raw Material Consumption Rates:

5. ACETONITRILE GRADES AND PURITY

6. APPLICATIONS AND INDUSTRIAL USES

Acetonitrile has a wide range of applications due to its high polarity, wide solubility range, low viscosity, and low UV absorbance.

6.1. Chromatography and Analytical Chemistry

Acetonitrile is one of the most widely used mobile phase solvents in high-performance liquid chromatography (HPLC). Its low UV absorbance (UV cutoff ~190 nm), low viscosity (0.35 cP), and wide solvent range make it ideal for HPLC applications. It is miscible with methanol and water in various ratios, and these mixtures allow the separation of analytes with different polarities. In LC-MS applications, acetonitrile's low ionization suppression and high purity make it a preferred solvent. In UV-spectrophotometric analysis, it is widely used as a solvent due to its low UV absorbance. In non-aqueous titrations, it is preferred due to its wide pH range and ability to dissolve ionic compounds.

6.2. Pharmaceutical and Chemical Industry

Acetonitrile is used as a solvent and intermediate in the synthesis of many active pharmaceutical ingredients in the pharmaceutical industry. Its high polarity and wide solubility range make it an ideal medium for many organic reactions. It is used as a solvent in many important reactions including Friedel-Crafts reactions, alkylation reactions, and nitrile chemistry. It is also an important intermediate in the synthesis of vitamins (especially B vitamins). It is also used in activated carbon production and in the synthesis of certain pesticides.

6.3. Polymer and Rubber Industry

Acetonitrile is used as a monomer in nitrile rubber (NBR - acrylonitrile-butadiene rubber) production. Nitrile rubber is a special type of rubber with high oil and solvent resistance and is used in automotive, aerospace, and petroleum industries for seals, hoses, and O-rings. It is also used as a solvent in the production and processing of various polymers.

6.4. Battery and Electrochemistry

Acetonitrile is widely used as an electrolyte solvent in lithium-ion batteries due to its high dielectric constant (36.6) and ionic conductivity. It dissolves lithium salts (such as LiPF₆, LiBF₄) well and optimizes the ionic conductivity of these salts. It is also used as an electrolyte solvent in supercapacitors and other electrochemical applications.

6.5. Other Applications

7. HEALTH EFFECTS AND TOXICOLOGY

Acetonitrile is a moderately toxic compound. Due to its metabolism to cyanide ion (CN⁻) in the body, acute poisoning causes symptoms similar to cyanide poisoning.

7.1. Toxicological Data

7.2. Mechanism of Toxicity

The toxicity of acetonitrile is due to its metabolism to cyanide ion (CN⁻) in the body. Metabolism occurs through the cytochrome P450 enzyme system:

CH₃CN → HCN (hydrogen cyanide)

Hydrogen cyanide inhibits cytochrome c oxidase in the mitochondrial respiratory chain, halting cellular respiration and causing tissue hypoxia (oxygen deficiency). This leads to symptoms similar to cyanide poisoning.

7.3. Health Effects

Acute Exposure:

Acetonitrile Poisoning Symptoms (Delayed):

Acetonitrile poisoning is characterized by symptoms appearing 2-12 hours after exposure, unlike cyanide poisoning. This delay is due to the time required for acetonitrile to metabolize to cyanide. Therefore, even if symptoms are not immediate, medical observation is essential after acetonitrile exposure.

• Early Symptoms: Headache, dizziness, nausea, vomiting, weakness, sweating.

• Late Symptoms (2-12 hours later): Breathing difficulty, chest tightness, palpitations, confusion, convulsions, respiratory arrest, coma, death.

Chronic Exposure:

• Liver and kidney damage (prolonged high exposure)

• Skin sensitization and dermatitis

• Nervous system effects (headache, dizziness, sleep disorders)

8. FIRST AID MEASURES

9. SAFETY INFORMATION (GHS CLASSIFICATION)

Signal Word: DANGER

Hazard Statements (H-Codes):

Precautionary Statements (P-Codes):

10. FIREFIGHTING MEASURES

11. ACCIDENTAL RELEASE MEASURES

12. STORAGE AND HANDLING

Acetonitrile should be stored at +5°C to +30°C in cool, well-ventilated areas, protected from direct sunlight. It should be kept away from ignition sources, heat, and oxidizing agents. It is incompatible with alkali metals, acids, bases, reducing agents, and oxidizing agents. All containers and equipment should be grounded to prevent static electricity accumulation. Explosion-proof electrical equipment should be used. Containers should be kept tightly closed and properly labeled.

Handling Notes:

• Use in well-ventilated areas

• Keep away from ignition sources

• Avoid static electricity accumulation

• Avoid contact with eyes, skin, and clothing

• Avoid breathing mist, vapor, or spray

• Use only with appropriate personal protective equipment

• Avoid release to the environment

• Cyanide poisoning risk; seek immediate medical attention in case of exposure

13. TRANSPORT INFORMATION

Acetonitrile is classified as a dangerous good with UN number 1648. Hazard class is 3 (Flammable Liquid) and Packing Group II. During transport, it should be kept away from heat, sparks, open flames, and other ignition sources. Containers should be grounded and bonded. It is not classified as a marine pollutant. Proper labeling and documentation are required during transport.

14. REGULATORY INFORMATION

Regulatory Status:

15. OTHER NAMES AND DATABASE IDENTIFIERS

Database Identifiers:

16. ENVIRONMENTAL INFORMATION

Acetonitrile is moderately toxic to aquatic organisms. It has low bioaccumulation potential (LogP -0.34). It is biodegradable under aerobic conditions. It volatilizes from water and soil and undergoes photochemical oxidation in the atmosphere. Waste disposal should be carried out according to local regulations; incineration is recommended. Discharge to sewers and water bodies should be avoided.

17. RAW MATERIALS AND DERIVATIVE PRODUCTS

17.1. Raw Materials (Upstream)

17.2. Derivative Products (Downstream)

18. TOXICOLOGICAL INFORMATION (DETAILED)

19. WORKPLACE SAFETY MEASURES

20. SUMMARY AND CRITICAL WARNINGS

SUMMARY:

Acetonitrile (C₂H₃N, CAS 75-05-8) is a polar aprotic solvent belonging to the nitrile class, containing a nitrile group (-C≡N). It is a colorless, clear liquid with a sweet, ether-like odor. The molecular weight is 41.05 g/mol, density is 0.7857 g/cm³, boiling point is 81-82°C, and flash point is 2°C. It is completely miscible with water, alcohols, ether, acetone, chloroform, and many organic solvents. It is produced by acetic acid ammonolysis, acetylene ammonolysis, or as a byproduct of propylene ammoxidation. Major applications include HPLC solvent, pharmaceutical intermediate, organic synthesis solvent, nitrile rubber (NBR) monomer, and lithium-ion battery electrolyte solvent. From a health perspective, it is moderately toxic; it is metabolized to cyanide ion (CN⁻) in the body, causing symptoms similar to cyanide poisoning. Symptoms may be delayed for 2-12 hours after exposure. It is highly flammable (flash point 2°C) and its vapor forms explosive mixtures with air (explosive limits 4.4-16.0%). IARC Group 3 (not classifiable as to carcinogenicity to humans). Classified as UN 1648 (Class 3 - Flammable Liquid, Packing Group II).

Key Properties:

Major Application Areas:

Toxicological Summary:

Key Safety Points:

• HIGHLY FLAMMABLE: Flash point 2°C; keep away from all ignition sources

• EXPLOSIVE MIXTURES: Forms explosive mixtures with air (4.4-16.0%); use explosion-proof equipment

• CYANIDE POISONING: Metabolizes to cyanide in the body; symptoms may be delayed (2-12 hours); medical observation after exposure is essential

• IRRITANT: Causes irritation to eyes, skin, and respiratory tract

• STORAGE: Store at +5°C to +30°C in cool, well-ventilated area away from ignition sources

• PPE REQUIRED: Chemical-resistant gloves, goggles, protective clothing, full-face respirator

• INCOMPATIBILITIES: Incompatible with alkali metals, acids, bases, oxidizing agents, and reducing agents

CRITICAL WARNINGS:

Cyanide Poisoning Risk: Acetonitrile is metabolized to hydrogen cyanide (HCN) in the body by the cytochrome P450 enzyme system. Cyanide inhibits the mitochondrial respiratory chain, halting cellular respiration. Acetonitrile poisoning is characterized by symptoms appearing 2-12 hours after exposure, unlike cyanide poisoning. This delay is due to the time required for acetonitrile to metabolize to cyanide. Symptoms include headache, dizziness, nausea, vomiting, breathing difficulty, convulsions, loss of consciousness, and death. Immediate medical attention is required after exposure, and symptom observation for 12 hours is essential. Cyanide antidotes (sodium thiosulfate, hydroxocobalamin) may be required.

Flammability and Explosion Risk: With a flash point of 2°C, acetonitrile is a highly flammable liquid. Vapors are heavier than air (vapor density 1.41) and may travel to ignition sources, causing flashback. Explosive limits range from 4.4-16.0% by volume. Static electricity accumulation can cause ignition. Use explosion-proof electrical equipment, proper grounding, and non-sparking tools.

Delayed Toxicity: One of the most dangerous aspects of acetonitrile poisoning is the delayed onset of symptoms. Symptoms may be mild or absent during the first hours after exposure. This can cause the victim to underestimate the exposure and delay treatment. Cyanide poisoning symptoms (dizziness, breathing difficulty, loss of consciousness) can appear suddenly 2-12 hours later. Therefore, even if symptoms are not immediate, medical observation is essential after acetonitrile exposure.

Storage and Stability: Acetonitrile is incompatible with alkali metals, acids, bases, reducing agents, and oxidizing agents. Contact with these substances can cause violent reactions and explosions. Store at +5°C to +30°C in cool, well-ventilated areas, protected from direct sunlight. Keep away from heat, ignition sources, and oxidizing agents.

HPLC Use: Acetonitrile is widely used as an HPLC mobile phase. However, high-purity (≥99.9%) acetonitrile is critical for low noise and high sensitivity in UV detectors. The UV cutoff is ~190 nm, so use below 200 nm wavelength is limited due to UV absorbance. Also, acetonitrile mixing with water is exothermic (releases heat); temperature increase during mixing should be monitored.

Environment: Acetonitrile is moderately toxic to aquatic organisms. Bioaccumulation potential is low. It volatilizes from water and soil and undergoes photochemical oxidation in the atmosphere. Discharge to sewers and water bodies should be avoided. Waste disposal should be carried out according to local regulations; incineration is recommended.

Important Disclaimer: This Technical Data Sheet (TDS) is for informational purposes only. The information provided is based on available data and is believed to be accurate. However, the user is solely responsible for determining the suitability of the product for their specific application and for complying with all applicable regulations and safety requirements. For complete safety, handling, storage, and regulatory compliance information, always refer to the official Safety Data Sheet (SDS/MSDS) provided by the manufacturer/supplier. Users are responsible for testing the product in their own processes and applications. All local, national, and international regulations must be followed when working with acetonitrile. Acetonitrile carries a cyanide poisoning risk; never use without expert training.