(Methyl cyanide, cyanomethane)
CAS 75-05-8



Physical Properties

Colorless liquid
bp 82 °C, mp -46 °C
Miscible with water (>100 g/100 mL)


Aromatic ether-like odor detectable at 40 ppm

Vapor Density

1.42 (air = 1.0)

Vapor Pressure

73 mmHg at 20 °C

Flash Point

6 °C

Autoignition Temperature

524 °C

Toxicity Data

LD50 oral (rat) 2730 mg/kg

LD50 skin (rabbit) 1250 mg/kg

LC50 inhal (rat) 7551 ppm (8 h)

PEL (OSHA) 40 ppm (70 mg/m3)

STEL (OSHA) 60 ppm (105 mg/m3)

TLV-TWA (ACGIH) 40 ppm (70 mg/m3)

STEL (ACGIH) 60 ppm (105 mg/m3)

Major Hazards

Flammable liquid and vapor; liquid severely irritates the eyes.


Acetonitrile is slightly toxic by acute exposure through oral intake, skin contact, and inhalation. However, acetonitrile can be converted by the body to cyanide. Symptoms of exposure include weakness, flushing, headache, difficult and/or rapid breathing, nausea, vomiting, diarrhea, blue-gray discoloration of the skin and lips (due to a lack of oxygen), stupor, and loss of consciousness. Acetonitrile is severely irritating to the eyes and slightly irritating to the skin. Prolonged contact can lead to absorption through the skin and more intense irritation. Acetonitrile is regarded as having adequate warning properties.

Acetonitrile is not mutagenic in bacterial and animal cells and has not been found to be a carcinogen in humans. Single high-dose exposure in animals during pregnancy produced birth defects possibly due to the liberation of cyanide. Multiple oral doses during pregnancy did not produce birth defects. Repeated exposure in animals produced adverse lung effects.

Flammability and Explosibility

Acetonitrile is a flammable liquid (NFPA rating = 3), and its vapor can travel a considerable distance to an ignition source and "flash back." Acetonitrile vapor forms explosive mixtures with air at concentrations of 4 to 16% (by volume). Hazardous gases produced in a fire include hydrogen cyanide, carbon monoxide, carbon dioxide, and oxides of nitrogen. Carbon dioxide or dry chemical extinguishers should be used for acetonitrile fires.

Reactivity and Incompatibility

Contact of acetonitrile with strong oxidizers can result in violent reactions. Acetonitrile hydrolyzes on exposure to strong acids and bases. It is incompatible with reducing agents and alkali metals and may attack plastics, rubber, and some coatings.

Storage and Handling

Acetonitrile should be handled in the laboratory using the "basic prudent practices" described in Chapter 5.C, supplemented by the additional precautions for dealing with highly flammable substances (Chapter 5.F). In particular, acetonitrile should be used only in areas free of ignition sources, and quantities greater than 1 liter should be stored in tightly sealed metal containers in areas separate from oxidizers.


In the event of skin contact, immediately wash with soap and water and remove contaminated clothing. In case of eye contact, promptly wash with copious amounts of water for 15 min (lifting upper and lower lids occasionally) and obtain medical attention. If acetonitrile is ingested, obtain medical attention immediately. If large amounts of this compound are inhaled, move the person to fresh air and seek medical attention at once.

In the event of a spill, remove all ignition sources, soak up the acetonitrile with a spill pillow or absorbent material, place in an appropriate container, and dispose of properly. Evacuation and cleanup using respiratory and skin protection may be necessary in the event of a large spill or release in a confined area.


Excess acetonitrile and waste material containing this substance should be placed in an appropriate container, clearly labeled, and handled according to your institution's waste disposal guidelines.

The information in this LCSS has been compiled by a committee of the National Research Council from literature sources and Material Safety Data Sheets and is believed to be accurate as of July 1994. This summary is intended for use by trained laboratory personnel in conjunction with the NRC report Prudent Practices in the Laboratory: Handling and Disposal of Chemicals. This LCSS presents a concise summary of safety information that should be adequate for most laboratory uses of the title substance, but in some cases it may be advisable to consult more comprehensive references. This information should not be used as a guide to the nonlaboratory use of this chemical.

Copyright 1995 National Academy of Sciences. All rights reserved.