Mesityl oxide

1Identification

Name

Mesityl oxide

IUPAC name

4-methylpent-3-en-2-one

CAS number

141-79-7

EC number

205-502-5

Molecular formula

C6H10O

Molecular weight

98.14 g/mol

InChIKey

SHOJXDKTYKFBRD-UHFFFAOYSA-N

SMILES

CC(=CC(=O)C)C

PubChem CID

8858

Synonyms

MESITYL OXIDE, 4-Methylpent-3-en-2-one, 4-Methyl-3-penten-2-one, Isopropylideneacetone, Methyl isobutenyl ketone, 3-Penten-2-one, 4-methyl-, Isobutenyl methyl ketone, Mesityloxid, Mesityloxyde, Ossido di mesitile, 3-Isohexen-2-one, Oxyde de mesityle, Methyl 2-methyl-1-propenyl ketone, Acetone, isopropylidene-

Recommended uses

• Mesityl oxide has many uses as an industrial solvent. It is used as a paint remover and insect repellent. [ACGIH] Used as a solvent for resins, lacquers, enamels, rubber, inks, and oils; [HSDB]
  Haz-Map, Information on Hazardous Chemicals and Occupational Diseases
• Painting (Solvents) [Category: Paint] Plastic Composites Manufacturing [Category: Industry]
  Haz-Map, Information on Hazardous Chemicals and Occupational Diseases
• Solvent for nitrocellulose, many gums and resins, particularly vinyl resins. In lacquers, varnishes and enamels. In making methyl isobutyl ketone.
  Hazardous Substances Data Bank (HSDB)
• Not Known or Reasonably Ascertainable
  EPA Chemical Data Reporting (CDR)
• Not Known or Reasonably Ascertainable
  EPA Chemical Data Reporting (CDR)

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

Description

• Mesityl oxide appears as a colorless, oily liquid with a pungent honey-like odor. Flash point 87 °F. Less dense than water and slightly soluble in water. Vapors heavier than air. Used in paint removers, as a solvent for plastics, and as an insect repellent.
  CAMEO Chemicals
• 4-Methyl-3-penten-2-one, 9CI is an olefinic compound. It is functionally related to an acrylic acid.
  ChEBI
• mesityl oxide has been reported in Bistorta manshuriensis, Tamarix aphylla, and other organisms with data available.
  LOTUS - the natural products occurrence database

2Hazard identification

Signal word

Warning

Pictograms

GHS02, GHS07

Classification source

Regulation (EC) No 1272/2008 of the European Parliament and of the Council

Precautionary statements

Other reported classifications

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

NFPA 704 rating

• 3 - Materials that, under emergency conditions, can cause serious or permanent 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)
• 1 - Materials that in themselves are normally stable but that can become unstable at elevated temperatures and pressures.
  Hazardous Substances Data Bank (HSDB)

Health hazards

• Inhalation causes irritation of nose and throat, headache, dizziness, difficult breathing. Contact with liquid or concentrated vapor causes severe eye irritation. Liquid irritates skin. Ingestion causes irritation of mouth and stomach. (USCG, 1999)
  CAMEO Chemicals
• · May cause toxic effects if inhaled or absorbed through skin. · Inhalation or contact with material may irritate or burn skin and eyes. · Fire will 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

• Behavior in Fire: Vapor is heavier than air and may travel a considerable distance to a source of ignition and flash back. (USCG, 1999)
  CAMEO Chemicals
• · HIGHLY FLAMMABLE: Will be easily ignited by heat, sparks or flames. · 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. · Containers may explode when heated. · Many liquids will float on water.
  Emergency Response Guidebook (ERG)
• Flammable. Above 25 °C explosive vapour/air mixtures may be formed.
  ILO-WHO International Chemical Safety Cards (ICSCs)

Hazards summary

• Liquid causes first degree burns on short exposure. [CHRIS] Narcosis is induced in acute inhalation studies, and animals develop renal tubular degeneration and hepatic necrosis in subchronic studies. [ACGIH] A lachrymator; [CHEMINFO] A skin irritant and severe eye irritant; [CAMEO]
  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

• Excerpt from NIOSH Pocket Guide for Mesityl oxide: Eye: IRRIGATE IMMEDIATELY - If this chemical contacts the eyes, immediately wash (irrigate) the eyes with large amounts of water, occasionally lifting the lower and upper lids. Get medical attention immediately. Skin: WATER FLUSH IMMEDIATELY - If this chemical contacts the skin, immediately flush the contaminated skin with water. If this chemical penetrates the clothing, immediately remove the clothing and flush the skin with water. Get medical attention promptly. Breathing: RESPIRATORY SUPPORT - If a person breathes large amounts of this chemical, move the exposed person to fresh air at once.
  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)
• (General first aid procedures) Eye: Irrigate immediately - If this chemical contacts the eyes, immediately wash (irrigate) the eyes with large amounts of water, occasionally lifting the lower and upper lids. Get medical attention immediately. Skin: Water flush immediately - If this chemical contacts the skin, immediately flush the contaminated skin with water. If this chemical penetrates the clothing, immediately remove the clothing and flush the skin with water. Get medical attention promptly. Breathing: Respiratory support Swallow: Medical attention immediately - If this chemical has been swallowed, get medical attention immediately.
  The National Institute for Occupational Safety and Health (NIOSH)

Symptoms of exposure

• Cough. Sore throat. Shortness of breath. Headache. Dizziness. Drowsiness. Unconsciousness. Respiratory and cardiac arrest.
  ILO-WHO International Chemical Safety Cards (ICSCs)
• Dry skin. Redness. Pain.
  ILO-WHO International Chemical Safety Cards (ICSCs)
• Redness. Pain.
  ILO-WHO International Chemical Safety Cards (ICSCs)

5Fire-fighting measures

• Use dry chemical, foam, carbon dioxide, or water spray. Water may be ineffective. Use water spray to keep fire-exposed containers cool.
  Hazardous Substances Data Bank (HSDB)
• If material /is/ on fire or involved in fire: Do not extinguish fire unless flow can be stopped. Use water in flooding quantities as fog. Solid streams of water may spread fire. Cool all affected containers with flooding quantities of water. Apply water from as far a distance as possible. Use "alcohol" foam, dry chemical or carbon dioxide.
  Hazardous Substances Data Bank (HSDB)
• Aqueous film-forming foam (AFFF), alcohol-resistant foam, powder, carbon dioxide.
  Hazardous Substances Data Bank (HSDB)

Hazardous combustion products

• Combustion may produce irritants and toxic gases.
  Hazardous Substances Data Bank (HSDB)

6Accidental release measures

Isolation and evacuation

• Excerpt from ERG Guide 129 [Flammable Liquids (Water-Miscible / Noxious)]: 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

• Personal protection: self-contained breathing apparatus. Ventilation. Do NOT let this chemical enter the environment. Collect leaking liquid in sealable 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)
• Eliminate all ignition sources. Stop or control the leak, if it can be done without undue risk. Use appropriate foam to blanket release and suppress vapors. Approach release from upwind. Absorb in noncombustible material for proper disposal.
  Hazardous Substances Data Bank (HSDB)
• Absorb on paper. Evaporate on a glass or iron dish in hood. Burn the paper.
  Hazardous Substances Data Bank (HSDB)
• Ventilation. Collect leaking liquid in sealable containers. Absorb remaining liquid in sand or inert absorbent and remove to safe place. Do NOT wash away into sewer. (Extra personal protection: self-contained breathing apparatus).
  Hazardous Substances Data Bank (HSDB)

7Handling and storage

• Fireproof. Separated from strong oxidants and acids. Do NOT store or transport in containers made from plastic or copper. Cool. Keep in the dark. Store in an area without drain or sewer access.
  ILO-WHO International Chemical Safety Cards (ICSCs)
• Fireproof. Separated from strong oxidants. Cool. Keep in the dark.
  Hazardous Substances Data Bank (HSDB)
• Protect containers against physical damage. Store well-ventilated cool place, isolating from oxidizing materials. Outdoor or isolated place from inhabitants is preferable. In case of outdoor storage, use standard combustible liquid storage room or cabinet.
  Hazardous Substances Data Bank (HSDB)

8Exposure controls / personal protection

Personal protective equipment

• Excerpt from NIOSH Pocket Guide for Mesityl oxide: Skin: PREVENT SKIN CONTACT - Wear appropriate personal protective clothing to prevent skin contact. Eyes: PREVENT EYE CONTACT - Wear appropriate eye protection to prevent eye contact. Wash skin: WHEN CONTAMINATED - The worker should immediately wash the skin when it becomes contaminated. Remove: WHEN WET (FLAMMABLE) - Work clothing that becomes wet should be immediately removed due to its flammability hazard (i.e., for liquids with a flash point <100 °F). Change: No recommendation is made specifying the need for the worker to change clothing after the workshift.
  CAMEO Chemicals
• Wear full protective clothing and positive pressure self-contained breathing apparatus.
  Hazardous Substances Data Bank (HSDB)
• Wear appropriate personal protective clothing to prevent skin contact.
  Hazardous Substances Data Bank (HSDB)
• Wear appropriate eye protection to prevent eye contact.
  Hazardous Substances Data Bank (HSDB)

Respirator recommendations

• NIOSH Up to 250 ppm: (APF = 25) Any supplied-air respirator operated in a continuous-flow mode (APF = 25) Any powered, air-purifying respirator with organic vapor cartridge(s) Up to 500 ppm: (APF = 50) Any chemical cartridge respirator with a full facepiece and organic vapor cartridge(s) (APF = 50) Any air-purifying, full-facepiece respirator (gas mask) with a chin-style, front- or back-mounted organic vapor canister (APF = 50) Any powered, air-purifying respirator with a tight-fitting facepiece and organic vapor cartridge(s) (APF = 50) Any self-contained breathing apparatus with a full facepiece (APF = 50) Any supplied-air respirator with a full facepiece Up to 1400 ppm: (APF = 2000) Any su…
  The National Institute for Occupational Safety and Health (NIOSH)

9Physical and chemical properties

10Stability and reactivity

Reactivity

• Mixing MESITYL OXIDE in equal molar proportions with any of the following substances in a closed container caused the temperature and pressure to increase: 2-aminoethanol, chlorosulfonic acid, ethylene diamine, nitric acid, oleum, or sulfuric acid [NFPA 1991].
  CAMEO Chemicals
• Highly flammable. Slightly soluble in water
  CAMEO Chemicals

Incompatible materials and hazardous reactions

• Mixing mesityl oxide and 2-aminoethanol /or chlorosulfonic acid or ethylene diamine or nitric acid or oleum or sulfuric acid/ in closed container caused temp and pressure to incr.
  Hazardous Substances Data Bank (HSDB)
• Oxidizers, acids.
  Hazardous Substances Data Bank (HSDB)
• ... Attacks many plastics.
  Hazardous Substances Data Bank (HSDB)

11Toxicological information

Target organs

• Eyes, skin, respiratory system, central nervous system, liver, kidneys
  The National Institute for Occupational Safety and Health (NIOSH)

Short-term exposure effects

• The substance is irritating to the eyes, skin and respiratory tract. Exposure far above the OEL could cause unconsciousness. If swallowed the substance may cause vomiting and could result in aspiration pneumonitis.
  ILO-WHO International Chemical Safety Cards (ICSCs)

Long-term exposure effects

• The substance defats the skin, which may cause dryness or cracking. The substance may have effects on the liver, kidneys and lungs.
  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: The most favorable course of action is to use an alternative chemical product with less inherent propensity for occupational exposure or environmental contamination. 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 soil or water; effects on animal, aquatic, and plant life; and conformance with environmental and public health regulations.
  Hazardous Substances Data Bank (HSDB)

14Transport information

UN number: UN 1229

Shipping name

• UN 1229; Mesityl oxide
  Hazardous Substances Data Bank (HSDB)
• IMO 3.3; Mesityl oxide
  Hazardous Substances Data Bank (HSDB)

DOT hazard class

• Mesityl oxide
  US Code of Federal Regulations, Hazardous Materials, 49 CFR Part 172
• UN1229
  US Code of Federal Regulations, Hazardous Materials, 49 CFR Part 172
• Class 3 Flammable and combustible liquid (49 eCFR § 173.120)
  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: III
  ILO-WHO International Chemical Safety Cards (ICSCs)

Emergency Response Guidebook

• 1229 129
  Emergency Response Guidebook (ERG)

How DOT hazard classes work →

15Regulatory information

• This action promulgates standards of performance for equipment leaks of Volatile Organic Compounds (VOC) in the Synthetic Organic Chemical Manufacturing Industry (SOCMI). The intended effect of these standards is to require all newly constructed, modified, and reconstructed SOCMI process units to use the best demonstrated system of continuous emission reduction for equipment leaks of VOC, considering costs, non air quality health and environmental impact and energy requirements. Mesityl oxide is produced, as an intermediate or a final product, by process units covered under this subpart.
  Hazardous Substances Data Bank (HSDB)
• Mesityl oxide is exempted from the requirement of a tolerance when used as a plant nutrient, cosolvent or solvent in accordance with good agricultural practice as inert (or occasionally active) ingredients in pesticide formulations applied to growing crops only. Limit: Not for use after edible parts of plant begin to form. Do not graze livestock in treated areas within 48 hr after application.
  Hazardous Substances Data Bank (HSDB)
• Pursuant to section 8(d) of TSCA, EPA promulgated a model Health and Safety Data Reporting Rule. The section 8(d) model rule requires manufacturers, importers, and processors of listed chemical substances and mixtures to submit to EPA copies and lists of unpublished health and safety studies. Mesityl oxide is included on this list.
  Hazardous Substances Data Bank (HSDB)

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

16Other information

Compiled from PubChem CID 8858 and the sources it aggregates (attributed inline). Data retrieved 2026-10-12. This summary describes the pure substance and is not a supplier SDS.