What Is Acrylonitrile?
Acrylonitrile, also known as acrylonitrile monomer or vinyl cyanide, is an organic compound with the chemical formula C3H3N and a molecular weight of 53.06 g/mol. Its CAS registry number is 107-13-1 and its EC number is 203-466-5. The molecule consists of a vinyl group attached to a nitrile group, which combines alkene-like and nitrile-like reactivity in a single small molecule.
Commercially, acrylonitrile is produced mainly by the ammoxidation of propylene, in which propylene, ammonia, and air react over a catalyst. It is one of the most important building blocks of the modern chemical industry because it feeds the production of fibers, plastics, rubbers, and carbon materials.
Physical Properties of Acrylonitrile
Pure acrylonitrile is a colorless, transparent liquid with a pungent, chloroform-like odor. The key physical constants are listed below.
| Property | Value |
|---|---|
| Chemical formula | C3H3N |
| Molecular weight | 53.06 g/mol |
| CAS number | 107-13-1 |
| EC number | 203-466-5 |
| Appearance | Colorless liquid with a chloroform-like odor |
| Melting point | -83.6°C |
| Boiling point | 77.3°C |
| Density at 20°C | 0.806 g/cm³ |
| Solubility in water | About 7.3 g per 100 mL at 20°C |
| Vapor pressure at 20°C | About 11.3 kPa |
Acrylonitrile is miscible with most organic solvents, including ethanol, diethyl ether, and acetone, and its partial solubility in water reflects its moderately polar character. Because of its low boiling point and high vapor pressure, the liquid evaporates readily, and vapor concentrations can build up quickly in poorly ventilated areas.
Chemical Properties and Reactivity
The molecular structure of acrylonitrile contains both a carbon-carbon double bond and a nitrile group, giving it the characteristic reactivity of alkenes and nitriles. The double bond undergoes addition reactions such as hydrogenation, halogenation, and hydration. For example, hydrogenation can produce propylamine-type products, and addition of hydrocyanic acid can form cyano-substituted propionic acid derivatives.
The electron-withdrawing nitrile group makes the double bond electron-poor, so acrylonitrile is highly reactive in nucleophilic addition and in polymerization. This is the basis of its most important industrial chemistry: free-radical polymerization of acrylonitrile yields polyacrylonitrile, and copolymerization with butadiene and styrene produces nitrile rubber and ABS resins. The nitrile group itself can also undergo hydrolysis to acrylic acid or amide derivatives and reduction to amines, enabling a wide range of downstream synthesis.
Toxicity and Safety Considerations
Acrylonitrile is a toxic and flammable substance. It is classified as a highly flammable liquid and vapor, corresponding to hazard statement H225 in the GHS system, and it is assigned UN number 1093 for transport. Exposure can occur by inhalation of vapor, skin absorption, or ingestion.
Acrylonitrile causes irritation of the skin, eyes, and respiratory tract, and inhalation of high vapor concentrations can lead to serious poisoning with symptoms such as headache, nausea, weakness, and in severe cases, respiratory depression. Because the liquid is readily absorbed through the skin, handling requires impermeable gloves, splash goggles, and protective clothing, together with local exhaust ventilation or enclosed systems. Workplace exposure should be monitored against occupational limits, and storage must be cool, dry, and well ventilated, away from ignition sources, strong bases, and oxidizing agents.
Major Applications of Acrylonitrile
The largest use of acrylonitrile is the production of acrylic fibers, which are valued for their softness, warmth, and resistance to sunlight and chemicals. A second major outlet is the manufacture of ABS resins, where acrylonitrile contributes heat resistance and chemical resistance to the styrene-butadiene matrix.
Additional applications include:
Nitrile rubber for hoses, seals, and oil-resistant products.
Acrylonitrile copolymers for barrier packaging materials.
Carbon fiber precursors via polyacrylonitrile, used in aerospace, automotive, and sporting goods.
Adiponitrile and other intermediates for nylon chemistry.
Fine chemicals such as acrylamide and specialty esters.
In the laboratory, acrylonitrile is used as a reactive monomer and as a building block for organic synthesis, always under fume hood conditions due to its volatility and toxicity.
Frequently Asked Questions
What is the chemical formula of acrylonitrile?
The chemical formula is C3H3N, and the molecular weight is 53.06 g/mol. Its CAS number is 107-13-1.
Is acrylonitrile flammable?
Yes. Acrylonitrile is a highly flammable liquid and vapor, with a boiling point of only 77.3°C and a low flash point, classified as H225 under GHS.
What are the main uses of acrylonitrile?
It is mainly used to make acrylic fibers, ABS resins, nitrile rubber, and polyacrylonitrile for carbon fiber, plus a range of chemical intermediates.
How does acrylonitrile react chemically?
Its double bond undergoes addition reactions such as hydrogenation and halogenation, and it polymerizes readily; its nitrile group participates in hydrolysis, reduction, and nucleophilic reactions.
Is acrylonitrile soluble in water?
It is partially soluble, about 7.3 g per 100 mL at 20°C, and fully miscible with most organic solvents such as ethanol, ether, and acetone.
What safety equipment is required when handling acrylonitrile?
Use impermeable gloves, splash goggles, and protective clothing, work under local exhaust ventilation, and monitor vapor concentrations because the liquid is absorbed through the skin and its vapor is toxic.
