What does acetonitrile mean?
Acetonitrile is a colourless, flammable liquid organic compound with the formula CH₃CN and a faintly sweet, ether-like odour. Chemically, it is the simplest organic nitrile — a carbon atom triple-bonded to nitrogen attached to a methyl group — which gives it unusual properties: it dissolves a remarkably wide range of substances while remaining stable toward many reagents. This combination makes it one of the most important solvents in modern chemistry. Its dominant use today is as the mobile phase in high-performance liquid chromatography (HPLC), where its transparency to ultraviolet light allows sensitive detection of dissolved compounds; it also serves in pharmaceutical manufacturing, DNA synthesis, and battery electrolytes. The name reflects both halves of the molecule, combining 'acet-' (from acetic acid) with 'nitrile'. Acetonitrile requires careful handling: it is toxic, and the body converts it into hydrogen cyanide. Despite this hazard, it remains indispensable in laboratories worldwide.
nounA colourless, volatile, sweet-smelling liquid organic compound (CH₃CN), the simplest organic nitrile, widely used as a polar aprotic solvent, notably in high-performance liquid chromatography and in the extraction of fatty acids.
- The chemical compound CH₃CN, a colourless liquid nitrile used as a polar aprotic solvent, especially in chromatography and organic synthesis.
"The chemists ran the sample through the column with acetonitrile as the mobile phase."
"Acetonitrile is the solvent of choice for reversed-phase HPLC because of its low UV absorbance."
"Workers must handle acetonitrile in a fume hood, since it metabolises into hydrogen cyanide in the body."
Rarely pluralised; as a pure chemical substance it is normally treated as a mass noun. Plural forms appear mainly when referring to different samples, grades, or isotopically labelled variants.
"The lab stocks several grades of acetonitriles for different analytical methods."
The same bottle of acetonitrile that helps labs identify trace drugs by chromatography is also what makes cigarette smoke contain hydrogen cyanide — it burns to produce it.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of acetonitrile
The name acetonitrile combines two roots: 'aceto-', derived ultimately from Latin acetum ('vinegar'), the same root behind acetic acid and acetone, and 'nitrile', a term coined in early nineteenth-century German chemistry (Nitril) for compounds containing the –C≡N group. The compound was first characterised in the mid-nineteenth century as a product of the dehydration of acetamide. Its sibling compounds sharing the acet- root include acetone, acetic acid, and acetyl chloride, while 'nitrile' connects it etymologically to the wider family of nitrogen-bearing compounds named after nitre (potassium nitrate).
How acetonitrile is actually used
Strictly technical register: acetonitrile appears almost exclusively in chemistry, laboratory, and industrial contexts and would be out of place in general conversation. In British spelling contexts it may be described as 'colourless' rather than 'colorless', but the word itself is spelled identically in all varieties of English.
Easily confused with acetonitrile
Acetylene is a gaseous hydrocarbon (C₂H₂) used in welding, whereas acetonitrile is a liquid nitrile solvent.
Acetaldehyde is an aldehyde produced during ethanol metabolism, while acetonitrile is a nitrile used chiefly as an industrial and laboratory solvent.