Mesitylene

1Identification

Name

Mesitylene

IUPAC name

1,3,5-trimethylbenzene

CAS number

108-67-8

EC number

203-604-4

Molecular formula

C9H12

Molecular weight

120.19 g/mol

InChIKey

AUHZEENZYGFFBQ-UHFFFAOYSA-N

SMILES

CC1=CC(=CC(=C1)C)C

PubChem CID

7947

Synonyms

1,3,5-Trimethylbenzene, sym-Trimethylbenzene, 3,5-Dimethyltoluene, Fleet-X, Trimethylbenzol, Benzene, 1,3,5-trimethyl-, Symmetrical trimethylbenzene, RefChem:6006, s-Trimethylbenzene, 2,4,6-trimethylbenzene, 1,3,5-trimethyl-benzene, Trimethylbenzene, 1,3,5-, Mesitylene, 98%, MESITYLENE [MI]

Recommended uses

• Found in coal tar and petroleum crudes; [Merck Index] Used to make dyes and UV oxidation stabilizers for plastics; Also used as a solvent and paint thinner; [HSDB]
  Haz-Map, Information on Hazardous Chemicals and Occupational Diseases
• Painting (Solvents) [Category: Paint]
  Haz-Map, Information on Hazardous Chemicals and Occupational Diseases
• DYESTUFF INTERMEDIATE, SOLVENT, PAINT THINNER
  Hazardous Substances Data Bank (HSDB)
• Fuel agents Other Solvent Intermediate Corrosion inhibitor
  EPA Chemical Data Reporting (CDR)
• Solvent Fuel Diluent Not Known or Reasonably Ascertainable
  EPA Chemical Data Reporting (CDR)

Use categories: Fragrance Ingredients

Description

• 1,3,5-trimethylbenzene appears as a colorless liquid with a peculiar odor. Insoluble in water and less dense than water. Flash point near 123 °F. May be toxic by ingestion and inhalation. Used to make plastics and dyes.
  CAMEO Chemicals
• 1,3,5-trimethylbenzene is a trimethylbenzene carrying methyl substituents at positions 1, 3 and 5.
  ChEBI
• structure
  Medical Subject Headings (MeSH)

2Hazard identification

Signal word

Warning

Pictograms

GHS02, GHS07, GHS09

Classification source

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

Precautionary statements

Other reported classifications

6 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)
• 2 - Materials that must be moderately heated or exposed to relatively high ambient temperatures before ignition can occur. Materials would not under normal conditions form hazardous atmospheres with air, but under high ambient temperatures or under moderate heating could release vapor in sufficient quantities to produce hazardous atmospheres with air.
  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 129 [Flammable Liquids (Water-Miscible / Noxious)]: 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. (ERG, 2024)
  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

• Excerpt from ERG Guide 129 [Flammable Liquids (Water-Miscible / Noxious)]: 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. (ERG, 2024)
  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 50 °C explosive vapour/air mixtures may be formed.
  ILO-WHO International Chemical Safety Cards (ICSCs)

Hazards summary

• A skin, eye, nose, throat and respiratory tract irritant; [Merck Index] A skin, eye, and respiratory tract irritant; Defats the skin; May have effects on the central nervous system and blood; [ICSC] A skin, eye, and respiratory tract irritant; [HSDB] A nose, throat, and lung irritant; Inhalation of high concentrations can cause CNS depression; [CHEMINFO] A respiratory tract irritant; [eChemPortal: ESIS] See Trimethyl benzene isomers.
  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 1,3,5-Trimethylbenzene: 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: SOAP WASH - If this chemical contacts the skin, wash the contaminated skin with soap and water. Breathing: RESPIRATORY SUPPORT - If a person breathes large amounts of this chemical, move the exposed person to fresh air at once. If breathing has stopped, perform artificial respiration. Keep the affected person warm and at rest. Get medical attention as soon as possible.
  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: Soap wash - If this chemical contacts the skin, wash the contaminated skin with soap and water. 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

• Confusion. Cough. Dizziness. Drowsiness. Headache. Sore throat. Vomiting.
  ILO-WHO International Chemical Safety Cards (ICSCs)
• Redness. Dry skin.
  ILO-WHO International Chemical Safety Cards (ICSCs)
• Redness. Pain.
  ILO-WHO International Chemical Safety Cards (ICSCs)

5Fire-fighting measures

• This chemical is a flammable liquid. Poisonous gases are produced in fire. Small fires: dry chemical, carbon dioxide, water spray, or alcohol foam. Large fires: water spray, fog, or alcohol foam. Move container from fire if you can do so without risk. Spray cooling water on containers that are exposed to flames until well after fire is out. For massive fire in cargo area, use unmanned hose holder or monitoring nozzles; if this is impossible, withdraw from area and let fire burn. Withdraw immediately in case of rising sound from venting safety device or any discoloration of tank due to fire. Isolate for one-half mile in all directions if tank car or truck is involved in fire.
  Hazardous Substances Data Bank (HSDB)
• If material on fire or involved in fire: Do not extinguish fire unless flow can be stopped or safely confined. Use water in flooding quantities as fog. Solid streams of water may be ineffective. Cool all affected containers with flooding quantities of water. Apply water from as far a distance as possible. Use foam, dry chemical, or carbon dioxide. Keep run-off water out of sewers and water sources.
  Hazardous Substances Data Bank (HSDB)

Hazardous combustion products

• The substance decomposes on burning producing toxic and irritating fumes.
  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: filter respirator for organic gases and vapours adapted to the airborne concentration of the substance. Do NOT wash away into sewer. Do NOT let this chemical enter the environment. Collect leaking and spilled liquid in sealable containers as far as possible. Absorb remaining liquid in sand or inert absorbent. Then store and dispose of according to local regulations.
  ILO-WHO International Chemical Safety Cards (ICSCs)
• 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, peat, carbon, or similar material and deposit in sealed containers. Keep this chemical out of a confined space ... because of the possibility of an explosion ... 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)
• Environmental considerations-water spill: Use natural barriers or oil spill control booms to limit spill travel. Remove trapped material with suction hoses.
  Hazardous Substances Data Bank (HSDB)

7Handling and storage

• Fireproof. Separated from strong oxidants. Well closed. Keep in a well-ventilated room.
  ILO-WHO International Chemical Safety Cards (ICSCs)
• Prior to working with this chemical you should be trained on its proper handling and storage. This chemical must be stored to avoid contact with oxidizers (such as perchlorates, peroxides, permanganates, chlorates, and nitrates), and strong oxidizers (such as chlorine, bromine, and fluorine) since violent reactions occur. Store in tightly closed containers in a cool, well-ventilated area away from heat. Sources of ignition such as smoking and open flames are prohibited where this chemical 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 this chemical should be grounded and bonded.
  Hazardous Substances Data Bank (HSDB)
• STORAGE TANKS SHOULD BE MOUNDED TO CONFINE ESCAPING LIQUID & ESCAPE FROM PROCESS VESSELS SHOULD BE CONTROLLED IN SIMILAR MANNER BY SILLS @ DOORWAYS, DESIGN OF FLOORS, ETC. /TRIMETHYLBENZENES/
  Hazardous Substances Data Bank (HSDB)

8Exposure controls / personal protection

Personal protective equipment

• Excerpt from NIOSH Pocket Guide for 1,3,5-Trimethylbenzene: 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 OR CONTAMINATED - Work clothing that becomes wet or significantly contaminated should be removed and replaced. Change: No recommendation is made specifying the need for the worker to change clothing after the workshift. (NIOSH, 2024)
  CAMEO Chemicals
• Wear protective gloves and clothing to prevent any reasonable probability of skin contact. Safety equipment suppliers/manufacturers can provide recommendations on the most protective glove/clothing material for your operation. All protective clothing (suits, gloves, footwear, headgear) should be clean, available for work each day, and put on before work. Contact lenses should not be worn when working with this chemical. Wear splash-proof chemical goggles and face shield unless full face-piece respiratory protection is worn. Employees should wash immediately with soap when skin is wet or contaminated. Provide emergency showers and eyewash.
  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

• Important additional information about respirator selection
  The National Institute for Occupational Safety and Health (NIOSH)

9Physical and chemical properties

10Stability and reactivity

Reactivity

• 1,3,5-TRIMETHYLBENZENE is incompatible with the following: Oxidizers, nitric acid (NIOSH, 2024).
  CAMEO Chemicals
• Flammable. Insoluble in water.
  CAMEO Chemicals

Incompatible materials and hazardous reactions

• Forms explosive mixture with air. Strong oxidizers cause fire and explosion hazard. Violent reaction with nitric acid.
  Hazardous Substances Data Bank (HSDB)
• Oxidizers, nitric acid.
  Hazardous Substances Data Bank (HSDB)
• Oxidizers, nitric acid
  The National Institute for Occupational Safety and Health (NIOSH)

11Toxicological information

Target organs

• Developmental Nervous
  EPA Integrated Risk Information System (IRIS)
• Eyes, skin, respiratory system, central nervous system, blood
  The National Institute for Occupational Safety and Health (NIOSH)

Short-term exposure effects

• The substance is irritating to the eyes, skin and respiratory tract. If this liquid is swallowed, aspiration into the lungs may result in chemical pneumonitis. The substance may cause effects on the central nervous system.
  ILO-WHO International Chemical Safety Cards (ICSCs)

Long-term exposure effects

• The substance defats the skin, which may cause dryness or cracking. Repeated or prolonged inhalation may cause effects on the lungs. This may result in chronic bronchitis. The substance may have effects on the central nervous system and blood.
  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)
• Incineration /SRP: with appropriate emission controls/.
  Hazardous Substances Data Bank (HSDB)

14Transport information

UN number: UN 2325

Shipping name

• UN 2325; 1,3,5-Trimethylbenzene
  Hazardous Substances Data Bank (HSDB)
• IMO 3.3; 1,3,5-Trimethylbenzene
  Hazardous Substances Data Bank (HSDB)

DOT hazard class

• Mesitylene
  US Code of Federal Regulations, Hazardous Materials, 49 CFR Part 172
• Marine pollutant
  US Code of Federal Regulations, Hazardous Materials, 49 CFR Part 172
• 1,3,5-Trimethylbenzene
  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

• 2325 129
  Emergency Response Guidebook (ERG)

How DOT hazard classes work →

15Regulatory information

• 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. 1,3,5-Trimethylbenzene is included on this list. Effective date: 2/13/1984; Sunset date: 2/13/1994.
  Hazardous Substances Data Bank (HSDB)

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

16Other information

Compiled from PubChem CID 7947 and the sources it aggregates (attributed inline). Data retrieved 2026-10-12. This summary describes the pure substance and is not a supplier SDS.