Substance profile
4-methylpent-3-en-2-one
4-methylpent-3-en-2-one is an oily, colorless to light-yellow liquid with a spearmint odor.
01 · Identification
What 4-methylpent-3-en-2-one is
4-methylpent-3-en-2-one is an oily, colorless to light-yellow liquid with a spearmint odor. Its molecular formula is C6H10O and its molecular weight is 98.14 g/mol. It boils at 130 °C, melts at -59 °C.
Under the GHS it carries the signal word Warning. It is classed as flammable agents - 3rd degree.
02 · Identifiers
4-methylpent-3-en-2-one identifiers and molecular data
4-methylpent-3-en-2-one CAS number and EC number
4-methylpent-3-en-2-one molecular formula and molecular weight
Other names for 4-methylpent-3-en-2-one
- mesityl oxide
03 · GHS classification
4-methylpent-3-en-2-one hazard classification
Harmonised classification under CLP Annex VI. This is the legally binding classification in the EU; other jurisdictions may differ.
4-methylpent-3-en-2-one pictograms and signal word
4-methylpent-3-en-2-one hazard class and category
| Hazard class | Category | From code | Pictogram |
|---|---|---|---|
| Flammable liquids GHS chapter 2.6 | Category 3 | H226 | GHS02 |
| Acute toxicity - oral GHS chapter 3.1 | Category 4 | H302 | GHS07 |
| Acute toxicity - dermal GHS chapter 3.1 | Category 4 | H312 | GHS07 |
| Acute toxicity - inhalation GHS chapter 3.1 | Category 4 | H332 | GHS07 |
4-methylpent-3-en-2-one hazard statements (H-codes)
| Code | Hazard statement |
|---|---|
| H226 | Flammable liquid and vapour. |
| H332 | Harmful if inhaled. |
| H312 | Harmful in contact with skin. |
| H302 | Harmful if swallowed. |
This page lists only the codes assigned to 4-methylpent-3-en-2-one. The full reference lives on the hazard statements hub, the precautionary statements hub and the GHS pictograms hub.
Safety Data Sheet
Getting an SDS for 4-methylpent-3-en-2-one
A Safety Data Sheet is written for a product, not for a substance: the supplier of the grade you actually buy issues it, so two suppliers of 4-methylpent-3-en-2-on… issue two different sheets. That is why there is no single authoritative SDS for a substance to download — what there is, is the job of collecting the sheets for the products you hold and keeping them current as suppliers revise them.
04 · Precautionary statements
4-methylpent-3-en-2-one precautionary statements
CLP Annex VI assigns 15 precautionary statements to 4-methylpent-3-en-2-one. They are grouped the way a label groups them: what to do before handling, what to do when something has already happened, how to store it and how to dispose of it.
Prevention
What to do before and during handling so the hazard never happens.
Response
What to do once exposure, spillage or fire has already happened.
Reading the notation. … is a blank the supplier fills in — not a truncated sentence.· [square brackets] mark a part printed only when it applies.
05 · Names in the regulation
4-methylpent-3-en-2-one name in 23 EU languages
CLP Annex VI Part 3 is published in every language edition of the regulation, and the identification column is written out in each of them. Nothing below is translated by us: each line is the name as that edition prints it. Under Art. 18(2) the substance name from Annex VI is a lawful product identifier, so this is the wording to put on a label going to that market — and where the cell lists several designations, any one of them qualifies.
| Language | Name in CLP Annex VI Part 3 |
|---|---|
| Bulgarian български | 4-метилпент-3-ен-2-он мезитилоксид |
| Spanish español | 4-Metilpent-3-en-2-ona óxido de mesitilo |
| Czech čeština | 4-methylpent-3-en-2-on mesityloxid |
| Danish dansk | 4-methyl-3-penten-2-on mesityloxid |
| German Deutsch | 4-Methylpent-3-en-2-on Mesityloxid |
| Estonian eesti | 4-metüülpent-3-een-2-oon mesitüüloksiid |
| Greek ελληνικά | 4-μεθυλοπεντ-3-εν-2-όνη μεσιτυλοξείδιο |
| English English | 4-methylpent-3-en-2-one mesityl oxide |
| French français | 4-méthylpent-3-én-2-one oxyde de mésityle |
| Croatian hrvatski | 4-metilpent-3-en-2-on mezitil-oksid |
| Italian italiano | 4-metilpent-3-en-2-one ossido di mesitile |
| Latvian latviešu | 4-metilpent-3-ēn-2-ons mezitiloksīds |
| Lithuanian lietuvių | 4-metil-3-penten-2-onas mezitiloksidas |
| Hungarian magyar | 4-metilpent-3-én-2-on mezitil-oxid |
| Maltese Malti | 4-metilpent-3-en-2-on ossidu tal-mesitil |
| Dutch Nederlands | 4-methyl-3-penteen-2-on mesityloxide |
| Polish polski | 4-metylopent-3-en-2-on tlenek mezytylu |
| Portuguese português | 4-metil-3-penten-2-ona óxido de mesitilo |
| Romanian română | 4-metil-3-penten-2-onă oxid de mesitil |
| Slovak slovenčina | 4-metylpent-3-én-2-ón mezityloxid |
| Slovenian slovenščina | 4-metilpent-3-en-2-on mezitil oksid |
| Finnish suomi | 4-metyylipent-3-en-2-oni mesityylioksidi |
| Swedish svenska | 4-metylpent-3-en-2-on mesityloxid |
All 23 language editions of Annex VI carry this entry. Irish is the twenty-fourth official EU language and has no line here for a different reason: no consolidated CLP text has ever been published in Irish, so there is no Irish edition of Annex VI to quote a name from. Source: consolidated CLP, CELEX 02008R1272, language editions. © European Union, https://eur-lex.europa.eu — only the electronic Official Journal of the European Union is authentic.
06 · Label elements
4-methylpent-3-en-2-one GHS label elements
Everything CLP Annex VI fixes for 4-methylpent-3-en-2-one, laid out the way it appears on a label. The greyed lines are the parts only the supplier can fill in.
Warning
4-methylpent-3-en-2-one
- Flammable liquid and vapour.
- Harmful if inhaled.
- Harmful in contact with skin.
- Harmful if swallowed.
- Keep away from heat, hot surfaces, sparks, open flames and other ignition sources. No smoking.
- Keep container tightly closed.
- Use explosion-proof [electrical/ventilating/lighting/…] equipment.
- Use only non-sparking tools.
- Do not breathe dust/fume/gas/mist/vapours/spray.
- Do not eat, drink or smoke when using this product.
- Use only outdoors or in a well-ventilated area.
- Wear protective gloves/protective clothing/eye protection/face protection/hearing protection/…
- IF SWALLOWED:
- IF ON SKIN:
- IF INHALED:
- Call a POISON CENTER/doctor/… if you feel unwell.
- Rinse mouth.
- Wash with plenty of water/…
- Store in a well-ventilated place.
Supplier name, address and telephone number· Product identifier·Nominal quantity
Need this as an actual label? Open 4-methylpent-3-en-2-one in the GHS label constructor →
07 · Health hazards
4-methylpent-3-en-2-one health hazards and exposure limits
4-methylpent-3-en-2-one hazard 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]
Source: Haz-Map, Information on Hazardous Chemicals and Occupational Diseases
4-methylpent-3-en-2-one occupational exposure limits
| Limit | Value | Source |
|---|---|---|
| PEL | 25.0 [ppm] | Haz-Map, Information on Hazardous Chemicals and Occupational Diseases |
| PEL | 25 ppm (100 mg/m³) | Occupational Safety and Health Administration (OSHA) |
| PEL | TWA 25 ppm (100 mg/m3) See Appendix G | The National Institute for Occupational Safety and Health (NIOSH) |
| REL | 10 ppm (40 mg/m³) | Occupational Safety and Health Administration (OSHA) |
| REL | TWA 10 ppm (40 mg/m3) | The National Institute for Occupational Safety and Health (NIOSH) |
| IDLH | 1400 ppm ; Based on 10% of the lower explosive limit. (NIOSH, 2024) | CAMEO Chemicals |
| IDLH | 1400.0 [ppm] | Haz-Map, Information on Hazardous Chemicals and Occupational Diseases |
| IDLH | 1400 ppm | Occupational Safety and Health Administration (OSHA) |
These are United States values. The European Union sets its own indicative and binding limits, and the figure that applies at a given workplace is the one in the local regulation — not the one shown here.
08 · Physical and chemical properties
4-methylpent-3-en-2-one properties
Every value is shown with the conditions it was measured under and the source it came from. Where sources disagree, all values are listed rather than one being picked — the difference is usually a different form of the substance, not an error.
4-methylpent-3-en-2-one boiling point
| Property | Value | Conditions | Source |
|---|---|---|---|
| Boiling point | 130 °C (266 °F) | at 760 mmHg | HSDB |
| 130 °C (266 °F) | NIOSH |
4-methylpent-3-en-2-one melting point
| Property | Value | Conditions | Source |
|---|---|---|---|
| Melting point | -59 °C (-74.2 °F) | HSDB | |
| -41.5 °C (-42.7 °F) | HSDB | ||
| -46.67 °C (-52 °F) | NIOSH |
4-methylpent-3-en-2-one density
| Property | Value | Conditions | Source |
|---|---|---|---|
| Density | 0.87 g/cm³ | ICSC | |
| 0.8508 g/cm³ | at 20 °C | HSDB | |
| 0.853 g/cm³ | at 20 °C | CAMEO |
4-methylpent-3-en-2-one solubility
| Property | Value | Conditions | Source |
|---|---|---|---|
| Solubility | Sol in about 30 parts water; miscible with most org liq | HSDB | |
| Miscible in ethanol, ethyl ether | HSDB | ||
| SLIGHTLY SOL IN PROPYLENE GLYCOL | HSDB |
4-methylpent-3-en-2-one vapor pressure
| Property | Value | Conditions | Source |
|---|---|---|---|
| Vapor pressure | 9 mmHg | NIOSH | |
| 8.21 mmHg | at 25 °C | HSDB |
4-methylpent-3-en-2-one flash point
| Property | Value | Conditions | Source |
|---|---|---|---|
| Flash point | 30.56 °C (87 °F) | HSDB | |
| 22.78 °C (73 °F) | CAMEO |
4-methylpent-3-en-2-one autoignition temperature
| Property | Value | Conditions | Source |
|---|---|---|---|
| Autoignition temperature | 344.44 °C (652 °F) | HSDB | |
| 340 °C (644 °F) | ICSC |
4-methylpent-3-en-2-one lower explosive limit (LEL)
| Property | Value | Conditions | Source |
|---|---|---|---|
| Lower explosive limit (LEL) | 1.4 % by volume | HSDB |
4-methylpent-3-en-2-one upper explosive limit (UEL)
| Property | Value | Conditions | Source |
|---|---|---|---|
| Upper explosive limit (UEL) | 7.2 % by volume | HSDB |
4-methylpent-3-en-2-one vapor density
| Property | Value | Conditions | Source |
|---|---|---|---|
| Vapor density | 3.4 (air = 1) | HSDB |
4-methylpent-3-en-2-one odor threshold
| Property | Value | Conditions | Source |
|---|---|---|---|
| Odor threshold | Odor low: 0.068 mg/cu m; Odor high: 100 mg/cu m. | HSDB | |
| Odor threshold values: 50% detection: 12 ppm; 100% detection: 25 ppm. | HSDB | ||
| The absolute perception limit has been reported to be 0.017 ppm. | HSDB |
Values compiled from PubChem Laboratory Chemical Safety Summary. Temperatures converted to Fahrenheit for reference.
09 · Fire and explosion
4-methylpent-3-en-2-one fire and explosion behaviour
These are descriptions rather than measured values, so they are kept out of the table above and quoted here with the source that reported them.
4-methylpent-3-en-2-one fire potential
Flammable liquid.
Source: Hazardous Substances Data Bank (HSDB)
10 · Handling and storage
4-methylpent-3-en-2-one storage and handling
4-methylpent-3-en-2-one safe 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.
Source: ILO-WHO International Chemical Safety Cards (ICSCs)
4-methylpent-3-en-2-one storage conditions
Fireproof. Separated from strong oxidants. Cool. Keep in the dark.
Source: Hazardous Substances Data Bank (HSDB)
4-methylpent-3-en-2-one incompatible materials
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.
Source: Hazardous Substances Data Bank (HSDB)
4-methylpent-3-en-2-one 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].
Source: CAMEO Chemicals
Planning storage for a mix of chemicals? Check 4-methylpent-3-en-2-one in the storage compatibility matrix →
11 · Transport
4-methylpent-3-en-2-one UN number and transport classification
Transport classification is a separate system from the GHS classification above. It decides how a package is marked and how a load may be carried; it does not follow from the workplace label, and the workplace label does not follow from it. The entries below are linked by CAS number, never by name.
4-methylpent-3-en-2-one under UN 1229 — shipping name, class and packing group
Europe · ADR 2025, Table A
| Proper shipping name (3.1.2) | Class | Classification code | PG | Labels (column 5) |
|---|---|---|---|---|
| MESITYL OXIDE | 3 | F1 | III | |
Source: ADR 2025, Table A of Chapter 3.2 · ECE/TRANS/352 Vol. I (UNECE). Class 3 is “Flammable liquids” (ADR 2.1.1.1).
United States · 49 CFR 172.101 Hazardous Materials Table
| Proper shipping name (column 2) | Class or division | PG | Labels (column 6) |
|---|---|---|---|
| Mesityl oxide | 3 | III | |
Source: 49 CFR 172.101 Hazardous Materials Table · eCFR, revision 2026-08-03. Class 3 is “Flammable and combustible liquid” (49 CFR 173.2).
12 · Questions
4-methylpent-3-en-2-one — frequently asked questions
What is the CAS number of 4-methylpent-3-en-2-one?
The CAS number of 4-methylpent-3-en-2-one is 141-79-7. Its EC number is 205-502-5.
What is the chemical formula of 4-methylpent-3-en-2-one?
The molecular formula of 4-methylpent-3-en-2-one is C6H10O and its molecular weight is 98.14 g/mol.
What does a 4-methylpent-3-en-2-one label have to show?
Under CLP Annex VI the label for 4-methylpent-3-en-2-one carries the pictograms Flame and Exclamation mark and the signal word is Warning.
Is 4-methylpent-3-en-2-one flammable?
Yes. CLP Annex VI assigns 4-methylpent-3-en-2-one H226 — flammable liquid and vapour. The flash point reported for it is 30.56 °C (87 °F) (HSDB).
Is 4-methylpent-3-en-2-one a carcinogen?
CLP Annex VI records no harmonised carcinogenicity classification for 4-methylpent-3-en-2-one. Annex VI is a list of agreed classifications, not a list of substances found safe, so this is an absence of a classification rather than a clean bill of health.
What is the exposure limit for 4-methylpent-3-en-2-one?
The US occupational exposure limit reported for 4-methylpent-3-en-2-one is 25.0 [ppm] (Haz-Map, Information on Hazardous Chemicals and Occupational Diseases). Limits differ by country: the EU sets its own indicative and binding values, and the figure that applies at a given workplace is the one in the local regulation.
What is the boiling point of 4-methylpent-3-en-2-one?
The boiling point reported for 4-methylpent-3-en-2-one is 130 °C (266 °F), at 760 mmHg (HSDB).
What is the melting point of 4-methylpent-3-en-2-one?
The melting point reported for 4-methylpent-3-en-2-one is -59 °C (-74.2 °F) (HSDB).
How should 4-methylpent-3-en-2-one be stored?
CLP Annex VI assigns 4-methylpent-3-en-2-one the storage statement P403. Fireproof. Separated from strong oxidants. Cool. Keep in the dark. (Hazardous Substances Data Bank (HSDB))
Nearby
Substances next to 4-methylpent-3-en-2-one
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