Butanedione

1Identification

Name

Butanedione

IUPAC name

butane-2,3-dione

CAS number

431-03-8

EC number

207-069-8

Molecular formula

C4H6O2

Molecular weight

86.09 g/mol

InChIKey

QSJXEFYPDANLFS-UHFFFAOYSA-N

SMILES

CC(=O)C(=O)C

PubChem CID

650

Synonyms

2,3-butanedione, diacetyl, biacetyl, Butane-2,3-dione, dimethylglyoxal, Butanedione, dimethyl diketone, Dimethyl glyoxal, 2,3-diketobutane, 2,3-dioxobutane, 2,3-Butadione, Glyoxal, dimethyl-, 2,3-butandione, Diketobutane

Recommended uses

• Used to carry aroma of butter and other food flavors; [Hawley] Diacetyl occurs naturally in butter, cheese, yogurt, milk, coffee, cocoa, honey, tobacco smoke, beer, wine, and a number of flowers and plant extracts; [ACGIH]
  Haz-Map, Information on Hazardous Chemicals and Occupational Diseases
• See Reference #2 for the OSHA National Emphasis Program--Microwave Popcorn Processing Plants.
  Haz-Map, Information on Hazardous Chemicals and Occupational Diseases
• Reported uses (ppm): Table: Reported uses (ppm): (Flavor and Extract Manufacturers' Association, 1994) [Table#993]
  Hazardous Substances Data Bank (HSDB)

Use categories: Fragrance Ingredients · Flavouring Agent -> FLAVOURING_AGENT -> JECFA Functional Classes · Flavoring Agents -> JECFA Flavorings Index

Description

• Diacetyl appears as a clear colorless liquid with a strong chlorine-like odor. Flash point 80 °F. Less dense than water. Vapors heavier than air.
  CAMEO Chemicals
• Butane-2,3-dione is an alpha-diketone that is butane substituted by oxo groups at positions 2 and 3. It is a metabolite produced during the malolactic fermentation. It has a role as a Saccharomyces cerevisiae metabolite and an Escherichia coli metabolite.
  ChEBI
• Diacetyl is a metabolite found in or produced by Escherichia coli (strain K12, MG1655).
  E. coli Metabolome Database (ECMDB)

2Hazard identification

Signal word

Danger

Pictograms

GHS02, GHS05, GHS06, GHS07, GHS08

Classification source

European Chemicals Agency (ECHA)

Precautionary statements

Other reported classifications

5 classification records exist across sources. Differences usually reflect purity, physical form or impurities.

NFPA 704 rating

• 2 - Materials that, under emergency conditions, can cause temporary incapacitation or residual injury.
  Hazardous Substances Data Bank (HSDB)
• 3 - Liquids and solids that can be ignited under almost all ambient temperature conditions. Materials produce hazardous atmospheres with air under almost all ambient temperatures or, though unaffected by ambient temperatures, are readily ignited under almost all conditions.
  Hazardous Substances Data Bank (HSDB)
• 0 - Materials that in themselves are normally stable, even under fire conditions.
  Hazardous Substances Data Bank (HSDB)

Health hazards

• Excerpt from ERG Guide 127 [Flammable Liquids (Water-Miscible)]: Inhalation or contact with material may irritate or burn skin and eyes. Fire may produce irritating, corrosive and/or toxic gases. Vapors may cause dizziness or asphyxiation, especially when in closed or confined areas. Runoff from fire control or dilution water may cause environmental contamination. (ERG, 2024)
  CAMEO Chemicals
• · Inhalation or contact with material may irritate or burn skin and eyes. · Fire may produce irritating, corrosive and/or toxic gases. · Vapors may cause dizziness or asphyxiation, especially when in closed or confined areas. · Runoff from fire control or dilution water may cause environmental contamination.
  Emergency Response Guidebook (ERG)

Fire hazards

• Excerpt from ERG Guide 127 [Flammable Liquids (Water-Miscible)]: HIGHLY FLAMMABLE: Will be easily ignited by heat, sparks or flames. CAUTION: Ethanol (UN1170) can burn with an invisible flame. Use an alternate method of detection (thermal camera, broom handle, etc.) Vapors may form explosive mixtures with air. Vapors may travel to source of ignition and flash back. Most vapors are heavier than air. They will spread along the ground and collect in low or confined areas (sewers, basements, tanks, etc.). Vapor explosion hazard indoors, outdoors or in sewers. Those substances designated with a (P) may polymerize explosively when heated or involved in a fire.
  CAMEO Chemicals
• · HIGHLY FLAMMABLE: Will be easily ignited by heat, sparks or flames. CAUTION: Ethanol (UN1170) can burn with an invisible flame. Use an alternate method of detection (thermal camera, broom handle, etc.) · Vapors may form explosive mixtures with air. · Vapors may travel to source of ignition and flash back. · Most vapors are heavier than air. They will spread along the ground and collect in low or confined areas (sewers, basements, tanks, etc.). · Vapor explosion hazard indoors, outdoors or in sewers. · Those substances designated with a (P) may polymerize explosively when heated or involved in a fire. · Runoff to sewer may create fire or explosion hazard.
  Emergency Response Guidebook (ERG)
• Highly flammable. Vapour/air mixtures are explosive.
  ILO-WHO International Chemical Safety Cards (ICSCs)

Hazards summary

• Little is currently known about which chemicals used in flavorings have the potential to cause lung disease and other health effects, and what workplace exposure concentrations are safe. As part of ongoing investigations into airways disease in microwave popcorn workers, NIOSH has recently undertaken animal experiments to evaluate individual butter flavoring chemicals. Results of an animal study indicate that exposure to vapors from diacetyl, a chemical used to impart butter-like flavor, causes airway injury, though perhaps to a smaller extent than that caused by exposure to vapors from the intact butter flavoring mixture itself.
  Haz-Map, Information on Hazardous Chemicals and Occupational Diseases

3Composition / information on ingredients

This page describes the pure substance. Commercial products may be solutions or mixtures. Check Section 3 of your supplier's SDS for concentrations and other ingredients.

4First-aid measures

• EYES: First check the victim for contact lenses and remove if present. Flush victim's eyes with water or normal saline solution for 20 to 30 minutes while simultaneously calling a hospital or poison control center. Do not put any ointments, oils, or medication in the victim's eyes without specific instructions from a physician. IMMEDIATELY transport the victim after flushing eyes to a hospital even if no symptoms (such as redness or irritation) develop. SKIN: IMMEDIATELY flood affected skin with water while removing and isolating all contaminated clothing. Gently wash all affected skin areas thoroughly with soap and water.
  CAMEO Chemicals
• General First Aid: · Call 911 or emergency medical service. · Ensure that medical personnel are aware of the material(s) involved, take precautions to protect themselves and avoid contamination. · Move victim to fresh air if it can be done safely. · Administer oxygen if breathing is difficult. · If victim is not breathing: -- DO NOT perform mouth-to-mouth resuscitation; the victim may have ingested or inhaled the substance. -- If equipped and pulse detected, wash face and mouth, then give artificial respiration using a proper respiratory medical device (bag-valve mask, pocket mask equipped with a one-way valve or other device).
  Emergency Response Guidebook (ERG)

Symptoms of exposure

• Cough. Drowsiness. Nausea. Headache. Sore throat.
  ILO-WHO International Chemical Safety Cards (ICSCs)
• Redness.
  ILO-WHO International Chemical Safety Cards (ICSCs)
• Redness. Pain. Burns.
  ILO-WHO International Chemical Safety Cards (ICSCs)

5Fire-fighting measures

• Suitable extinguishing media: For small (incipient) fires, use media such as "alcohol" foam, dry chemical, or carbon dioxide. For large fires, apply water from as far as possible. Use very large quantities (flooding) of water applied as a mist or spray; solid streams of water may be ineffective. Cool all affected containers with flooding quantities of water.
  Hazardous Substances Data Bank (HSDB)
• Advice for firefighters: Wear self-contained breathing apparatus for firefighting if necessary.
  Hazardous Substances Data Bank (HSDB)
• Use water spray to cool unopened containers.
  Hazardous Substances Data Bank (HSDB)

Hazardous combustion products

• Special hazards arising from the substance or mixture: Carbon oxides
  Hazardous Substances Data Bank (HSDB)

6Accidental release measures

Isolation and evacuation

• Excerpt from ERG Guide 127 [Flammable Liquids (Water-Miscible)]: IMMEDIATE PRECAUTIONARY MEASURE: Isolate spill or leak area for at least 50 meters (150 feet) in all directions. LARGE SPILL: Consider initial downwind evacuation for at least 300 meters (1000 feet). FIRE: If tank, rail tank car or highway tank is involved in a fire, ISOLATE for 800 meters (1/2 mile) in all directions; also, consider initial evacuation for 800 meters (1/2 mile) in all directions. (ERG, 2024)
  CAMEO Chemicals
• Immediate precautionary measure · Isolate spill or leak area for at least 50 meters (150 feet) in all directions. Large Spill · Consider initial downwind evacuation for at least 300 meters (1000 feet). Fire · If tank, rail tank car or highway tank is involved in a fire, ISOLATE for 800 meters (1/2 mile) in all directions; also, consider initial evacuation for 800 meters (1/2 mile) in all directions.
  Emergency Response Guidebook (ERG)

Spill cleanup

• Remove all ignition sources. Personal protection: filter respirator for organic gases and vapours adapted to the airborne concentration of the substance. Do NOT let this chemical enter the environment. Collect leaking liquid in covered containers. Absorb remaining liquid in sand or inert absorbent. Then store and dispose of according to local regulations.
  ILO-WHO International Chemical Safety Cards (ICSCs)
• ACCIDENTAL RELEASE MEASURES: Personal precautions, protective equipment and emergency procedures: Wear respiratory protection. Avoid breathing vapors, mist or gas. Ensure adequate ventilation. Remove all sources of ignition. Evacuate personnel to safe areas. Beware of vapors accumulating to form explosive concentrations. Vapors can accumulate in low areas. Environmental precautions: Prevent further leakage or spillage if safe to do so. Do not let product enter drains. Methods and materials for containment and cleaning up: Contain spillage, and then collect with an electrically protected vacuum cleaner or by wet-brushing and place in container for disposal according to local regulations.
  Hazardous Substances Data Bank (HSDB)
• Evacuate and restrict persons not wearing protective equipment from area of spill or leak until cleanup is complete. Remove all ignition sources. Ventilate area of spill or leak. Absorb liquids in vermiculite, dry sand, earth, or a similar material and deposit in sealed containers. Keep butanedione out of confined space, such as a sewer, because of the possibility of an explosion, unless the sewer is designed to prevent the build up of explosive concentrations. It may be necessary to contain and dispose of this chemical as a hazardous waste. If material or contaminated runoff enters waterways, notify downstream users of potentially contaminated waters.
  Hazardous Substances Data Bank (HSDB)
• Environmental considerations--land spill: Dig a pit, pond, lagoon, holding area to contain liquid or solid material. /SRP: If time permits, pits, ponds, lagoons, soak holes, or holding areas should be sealed with an impermeable flexible membrane liner./ Dike surface flow using soil, sand bags, foamed polyurethane, or foamed concrete. Absorb bulk liquid with fly ash, cement powder, or commercial sorbents.
  Hazardous Substances Data Bank (HSDB)

7Handling and storage

• Fireproof. Store in an area without drain or sewer access. Separated from : see Chemical Dangers.
  ILO-WHO International Chemical Safety Cards (ICSCs)
• Store in cool place. Keep container tightly closed in a dry and well-ventilated place. Containers which are opened must be carefully resealed and kept upright to prevent leakage. Recommended storage temperature 2 - 8 °C. Storage class (TRGS 510): Flammable liquids.
  Hazardous Substances Data Bank (HSDB)
• Store in a flammable liquid storage area or approved cabinet away from ignition sources and corrosive and reactive materials. Store in tightly closed containers in a cool, well-ventilated area. Sources of ignition, such as smoking and open flames, are prohibited where butanedione is used, handled, or stored in a manner that could create a potential fire or explosion hazard. Metal containers involving the transfer of 5 gallons or more of butanedione should be grounded and bonded. Drums must be equipped with self-closing valves, pressure vacuum bungs and flame arresters. Use only nonsparking tools and equipment, especially when opening and closing containers of butanedione.
  Hazardous Substances Data Bank (HSDB)

8Exposure controls / personal protection

Personal protective equipment

• Excerpt from ERG Guide 127 [Flammable Liquids (Water-Miscible)]: Wear positive pressure self-contained breathing apparatus (SCBA). Structural firefighters' protective clothing provides thermal protection but only limited chemical protection. (ERG, 2024)
  CAMEO Chemicals
• Eye/face protection: Tightly fitting safety goggles. Faceshield (8-inch minimum). Use equipment for eye protection tested and approved under appropriate government standards such as NIOSH (US) or EN 166(EU).
  Hazardous Substances Data Bank (HSDB)
• Skin protection: Handle with gloves.
  Hazardous Substances Data Bank (HSDB)
• Body Protection: Long sleeved clothing. Preventive skin protection. Complete suit protecting against chemicals. Flame retardant antistatic protective clothing. The type of protective equipment must be selected according to the concentration and amount of the dangerous substance at the specific workplace.
  Hazardous Substances Data Bank (HSDB)

9Physical and chemical properties

10Stability and reactivity

Reactivity

• DIACETYL is a flammable liquid, b.p. 88 °C, moderately toxic. When heated to decomposition it emits acrid smoke and fumes [Sax, 9th ed., 1996, p. 544].
  CAMEO Chemicals
• Highly flammable. Soluble in water.
  CAMEO Chemicals

Incompatible materials and hazardous reactions

• Incompatible materials: Oxidizing agents, strong bases, reducing agents, metals
  Hazardous Substances Data Bank (HSDB)
• Contact with oxidizers may cause fire and explosions. High heat may cause violent combustion or explosion.
  Hazardous Substances Data Bank (HSDB)

Chemical stability

• Stable under recommended storage conditions.
  Hazardous Substances Data Bank (HSDB)

11Toxicological information

Short-term exposure effects

• The substance is severely irritating to the eyes. The substance is irritating to the skin and respiratory tract. The substance may cause effects on the central nervous system, lungs and respiratory tract. Exposure at high levels could cause lowering of consciousness.
  ILO-WHO International Chemical Safety Cards (ICSCs)

Long-term exposure effects

• Lungs may be affected by repeated or prolongated exposure to the vapour. This may result in impaired functions.
  ILO-WHO International Chemical Safety Cards (ICSCs)

12Ecological information

Not available in the public sources we compile. Check Section 12 of the supplier's SDS.

13Disposal considerations

• SRP: Recycle any unused portion of the material for its approved use or return it to the manufacturer or supplier. Ultimate disposal of the chemical must consider: the material's impact on air quality; potential migration in air, soil or water; effects on animal, aquatic and plant life; and conformance with environmental and public health regulations. If it is possible or reasonable use an alternative chemical product with less inherent propensity for occupational harm/injury/toxicity or environmental contamination.
  Hazardous Substances Data Bank (HSDB)
• SRP: Wastewater from contaminant suppression, cleaning of protective clothing/equipment, or contaminated sites should be contained and evaluated for subject chemical or decomposition product concentrations. Concentrations shall be lower than applicable environmental discharge or disposal criteria. Alternatively, pretreatment and/or discharge to a permitted wastewater treatment facility is acceptable only after review by the governing authority and assurance that "pass through" violations will not occur. Due consideration shall be given to remediation worker exposure (inhalation, dermal and ingestion) as well as fate during treatment, transfer and disposal.
  Hazardous Substances Data Bank (HSDB)
• Product: Burn in a chemical incinerator equipped with an afterburner and scrubber but exert extra care in igniting as this material is highly flammable. Offer surplus and non-recyclable solutions to a licensed disposal company. Contact a licensed professional waste disposal service to dispose of this material. Contaminated packaging: Dispose of as unused product.
  Hazardous Substances Data Bank (HSDB)

14Transport information

UN number: UN 2346

Shipping name

• UN 2346; Butanedione
  Hazardous Substances Data Bank (HSDB)
• IMO 3; Butanedione
  Hazardous Substances Data Bank (HSDB)

DOT hazard class

• Butanedione
  US Code of Federal Regulations, Hazardous Materials, 49 CFR Part 172
• Marine pollutant
  US Code of Federal Regulations, Hazardous Materials, 49 CFR Part 172
• UN2346
  US Code of Federal Regulations, Hazardous Materials, 49 CFR Part 172

DOT label

• Flammable Liquid
  CAMEO Chemicals

UN classification

• UN Hazard Class: 3; UN Pack Group: II
  ILO-WHO International Chemical Safety Cards (ICSCs)

Emergency Response Guidebook

• 2346 127
  Emergency Response Guidebook (ERG)

How DOT hazard classes work →

15Regulatory information

• Substance added directly to human food affirmed as generally recognized as safe (GRAS).
  Hazardous Substances Data Bank (HSDB)

Overview of SDS regulations (OSHA HazCom, WHMIS, REACH/CLP) →

16Other information

Compiled from PubChem CID 650 and the sources it aggregates (attributed inline). Data retrieved 2026-10-12. This summary describes the pure substance and is not a supplier SDS.