Quick Answer: Acetonitrile (CH₃CN, CAS 75-05-8) is a highly flammable solvent (flash point 6°C) and a toxic chemical whose primary danger comes from its metabolism in the body to cyanide - a process that can delay symptoms of serious poisoning by several hours after exposure.
Acetonitrile (CH₃CN, CAS 75-05-8), also known as methyl cyanide, is a colorless, transparent liquid with exceptional solvent properties - infinitely miscible with water and alcohols and widely used as an HPLC mobile phase, an organic-synthesis solvent and an industrial extractant. It is also a highly toxic chemical, and its hazard profile has one feature that must be understood first: acetonitrile is metabolized in the body to cyanide.
1. The Core Mechanism: Cyanide Release In The Body
Acetonitrile itself is not what causes the most severe poisoning. The compound is metabolized in the liver to cyanide ions, which inhibit cytochrome oxidase and block the cells' ability to use oxygen - producing a chemical asphyxiation at the cellular level. Because this conversion takes time, symptoms of significant exposure can be delayed by several hours, and a person who feels fine immediately after exposure can deteriorate later. Any significant exposure to acetonitrile - especially ingestion or inhalation of concentrated vapour - must be treated as a medical emergency, with the patient observed and, for serious cases, treated with the standard cyanide antidote protocol (amyl nitrite/sodium nitrite and sodium thiosulfate) under medical direction.
This is general safety information and is not a substitute for professional medical guidance. In an actual exposure or poisoning event, contact emergency medical services or a poison control center immediately.
2. Physical And Fire Hazards
| Property | Value |
|---|---|
| Flash point | 6 °C (closed cup) - highly flammable |
| Explosive range in air | 4–16% (v/v) |
| Boiling point / density | 81.6 °C / 0.786 g/cm³ |
| Vapour behaviour | Vapours are heavier than air and can travel to ignition sources |
| Exposure limit (TLV-TWA) | 20 ppm (ACGIH) |
| Immediately dangerous to life (IDLH) | 500 ppm |
3. Health Hazards By Route
- Skin and mucous membranes: highly irritating; prolonged or repeated skin contact can cause redness, itching and pain; the liquid is absorbed through the skin.
- Respiratory system: vapour irritates the airways, causing coughing, chest tightness and shortness of breath; inhalation of high concentrations leads to the cyanide-type systemic effects described above.
- Nervous system: prolonged exposure or significant acute exposure can cause headache, dizziness, insomnia and memory impairment; severe cases progress to confusion, convulsions or coma - consistent with cyanide-mediated tissue hypoxia.
- Liver: acetonitrile is primarily metabolized by the liver; long-term overexposure can overload the organ, with symptoms such as loss of appetite and fatigue.
4. Emergency Measures (First Aid)
- Skin contact: remove contaminated clothing, rinse thoroughly with water for at least 15 minutes.
- Eye contact: flush with water for at least 15 minutes, lifting the lids; seek medical attention.
- Inhalation: move to fresh air; if breathing is difficult, give oxygen; significant exposure requires immediate medical evaluation because of the delayed cyanide effect.
- Ingestion: do not induce vomiting; seek emergency medical care immediately - this route has the highest cyanide risk.
5. Safe Handling And Storage
Use in a fume hood or with effective local exhaust ventilation; monitor airborne concentrations where large volumes are handled.
Wear chemical-resistant gloves, splash goggles and protective clothing; avoid open flames, sparks and hot surfaces - the flash point is 6 °C.
Store in tightly closed containers in a cool, well-ventilated area away from heat, ignition sources, strong oxidizers, acids and reducing agents.
Bond and ground containers during transfer to prevent static ignition. For full first aid, exposure control and disposal procedures, refer to the acetonitrile SDS.
6. Disposal
Dispose of acetonitrile and contaminated materials as hazardous chemical waste through a licensed facility; do not pour into drains or sewers. Label waste containers clearly and keep them segregated from incompatible materials.
Frequently Asked Questions
Is Acetonitrile Toxic To Humans?
Yes. Acetonitrile is metabolized in the body to cyanide, which blocks cellular oxygen use. Toxicity is delayed rather than immediate, meaning a person can appear unaffected for hours after significant exposure before symptoms develop.
What Happens If You Inhale Acetonitrile?
Inhaling acetonitrile vapour irritates the respiratory tract, causing coughing and chest tightness at lower concentrations. At high concentrations, absorbed acetonitrile is metabolized to cyanide, which can cause headache, dizziness, confusion and, in severe cases, seizures or coma as symptoms develop over several hours.
Is Acetonitrile Flammable?
Yes. Acetonitrile has a flash point of 6°C and an explosive range of 4–16% in air, making it a highly flammable liquid that requires storage away from heat and ignition sources.
What Is The Antidote For Acetonitrile Poisoning?
Severe acetonitrile poisoning is treated using the standard cyanide antidote protocol - amyl nitrite/sodium nitrite and sodium thiosulfate - administered under medical direction. This must only be given by trained medical personnel; anyone with suspected significant exposure should seek emergency care immediately.
Working with HPLC-grade or industrial acetonitrile? See our full guide to acetonitrile as a solvent for grade specifications and applications, or contact our technical team for COA and handling documentation.
