acetonitrile

Acetonitrile, also called cyanomethane, is an organic solvent with the chemical formula CH3CN. It is a colorless, volatile liquid that is miscible with water and most organic solvents. As a polar aprotic solvent, it has a relatively high dielectric constant and is widely used in chemical synthesis and analysis.

Its physical properties include a boiling point of 81.6°C, a melting point around −45°C, and a density of about 0.786 g/mL at 25°C. It is flammable with a low flash point (approximately −22°C). Acetonitrile is highly polar and has UV transparency suitable for chromatographic applications, and it is miscible with water in all proportions.

Industrial production is typically via hydrocyanation of acetaldehyde to form acetaldehyde cyanohydrin, which is dehydrated to acetonitrile. It can also be obtained as a byproduct in the manufacture of acrylonitrile. The compound is relatively stable but toxic, and handling requires proper ventilation.

Major uses include as a solvent in organic synthesis and high-performance liquid chromatography (HPLC) due to low UV absorption and good solvating power. It is also used as a solvent in electrochemical applications, including lithium-ion battery electrolytes. It serves as a precursor to various nitrile- and amide-containing compounds via hydrolysis or reduction.

Safety and environment: acetonitrile is flammable and toxic; inhalation or ingestion can be harmful. It can release cyanide upon metabolic breakdown; exposure limits are established by safety agencies. It should be stored in a tightly closed container in a cool, well-ventilated place away from oxidizers. Spills should be contained to prevent entry into waterways and treated as hazardous waste.