What Is Acetonitrile?
Acetonitrile is a clear, colorless liquid with CAS RN® 75-05-8. It is chemically stable, soluble in water and alcohols, and in many organic compounds, making it an indispensable substance in industry.
Acetonitrile has the molecular formula C₂H₃N, molecular weight of 41.05, boiling point of 81.6°C, melting point of -45°C, and specific gravity of 0.783. It has a high dielectric constant of 37.5 and mixes well with water. It is hydrophobic with a methyl group CH3 and polarized nitrile CN, making it a molecule with both hydrophobicity and polarity and is one of the polar aprotic solvents, which are polar solvents without hydroxyl groups.
Because of its hazardous effects on health, it must be used under appropriate management.
Uses of Acetonitrile
The following are three uses of acetonitrile:
1. Solvents and Analytical Reagents
Acetonitrile is used as a solvent for organic synthesis reactions and purification and as an analytical reagent. It can be uniformly mixed with water and organic solvents, dissolving many compounds. It is an excellent HPLC solvent, solubilizing octadecyl group carriers used in reversed-phase HPLC.
Due to its low UV absorption, it provides good chromatograms with low background signal in HPLC combined with UV detection. Compared to methanol, another common HPLC solvent, acetonitrile has superior separation ability and its low viscosity lowers the pressure during use.
2. Dissolution of Polar Substances
As a polar aprotic solvent, acetonitrile is used to dissolve polar substances without water. It is employed in non-aqueous reactions using AlCl3 and POCl3, where water should not be present. Its high dielectric property enhances the reaction rate in synthetic organic reactions, serving as a solvent to provide a reaction field.
3. Pesticides, Pharmaceuticals, Etc.
Acetonitrile, like other nitrile compounds, is used in organic synthesis, leveraging the reactivity of cyano groups. It is utilized in agrochemicals, pharmaceuticals, dyes, synthetic resin modifiers, epoxy resin curing agents, etc. It forms binary azeotropic mixtures with many organic solvents and is used as an extraction and distillation solvent in the petroleum refining field, specifically in separating olefins from paraffin-olefin mixtures.
Future applications include use as an electrolyte for secondary batteries, a solvent for organic EL material synthesis, and for cleaning electronic components, as well as in DNA synthesis and purification.
Types of Acetonitrile
Reflecting its diverse uses, acetonitrile products with controlled impurities are available for different applications. Analytical reagents include those for HPLC, LC/MS, pesticide residue, and PCB testing.
Other Information on Acetonitrile
Acetonitrile Supply Issues
Acetonitrile is mostly obtained as a byproduct of acrylonitrile production. Fluctuations in the automobile industry, which uses acrylonitrile in ABS resin, affect the supply of acetonitrile. Recent concerns over its supply were raised during the 2020 global coronavirus outbreak, impacting automobile plant operations.
Companies handling acetonitrile are striving to ensure stable supply through securing raw materials, setting up their plants, and exploring alternative synthesis methods. Meanwhile, HPLC manufacturers are developing equipment that uses less solvent to mitigate the impact of acetonitrile supply issues on users’ businesses.