Substance profile
Diketene
Diketene is a colorless liquid; turns brownish-yellow upon standing at room temperature with a pungent odor.
01 · Identification
What Diketene is
Diketene is a colorless liquid; turns brownish-yellow upon standing at room temperature with a pungent odor. Its molecular formula is C4H4O2 and its molecular weight is 84.07 g/mol. It boils at 127 °C, melts at -6.5 °C.
Under the GHS it carries the signal word Warning. It is classed as flammable agents - 3rd degree.
02 · Identifiers
Diketene identifiers and molecular data
Diketene CAS number and EC number
Diketene molecular formula and molecular weight
Other names for Diketene
- diketen
03 · GHS classification
Diketene hazard classification
Harmonised classification under CLP Annex VI. This is the legally binding classification in the EU; other jurisdictions may differ.
Diketene pictograms and signal word
Diketene hazard class and category
| Hazard class | Category | From code | Pictogram |
|---|---|---|---|
| Flammable liquids GHS chapter 2.6 | Category 3 | H226 | GHS02 |
| Acute toxicity - inhalation GHS chapter 3.1 | Category 4 | H332 | GHS07 |
Diketene hazard statements (H-codes)
| Code | Hazard statement |
|---|---|
| H226 | Flammable liquid and vapour. |
| H332 | Harmful if inhaled. |
This page lists only the codes assigned to Diketene. 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 Diketene
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 Diketene 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
Diketene precautionary statements
CLP Annex VI assigns 9 precautionary statements to Diketene. 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
Diketene 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 | дикетен |
| Spanish español | Diceteno dicetén |
| Czech čeština | diketen |
| Danish dansk | acetylketen diketen |
| German Deutsch | Diketen 4-Methylen-2-oxetanon |
| Estonian eesti | diketeen |
| Greek ελληνικά | δικετένη δικετένιο |
| English English | diketene diketen |
| French français | dicétène |
| Croatian hrvatski | diketen |
| Italian italiano | dichetene |
| Latvian latviešu | diketēns |
| Lithuanian lietuvių | diketenas diketen |
| Hungarian magyar | diketén |
| Maltese Malti | diketena diketen |
| Dutch Nederlands | diketeen diketen |
| Polish polski | diketen 4-metylidenooksetan-2-on |
| Portuguese português | diceteno |
| Romanian română | dicetenă diceten |
| Slovak slovenčina | diketén 4-metylidénoxetán-2-ón |
| Slovenian slovenščina | diketen |
| Finnish suomi | diketeeni |
| Swedish svenska | diketen acetylketen4-metylen-2-oxetanon |
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
Diketene GHS label elements
Everything CLP Annex VI fixes for Diketene, laid out the way it appears on a label. The greyed lines are the parts only the supplier can fill in.
Warning
Diketene
- Flammable liquid and vapour.
- Harmful if inhaled.
- 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.
- Use only outdoors or in a well-ventilated area.
- IF INHALED:
- Call a POISON CENTER/doctor/… if you feel unwell.
- Store in a well-ventilated place.
Supplier name, address and telephone number· Product identifier·Nominal quantity
Need this as an actual label? Open Diketene in the GHS label constructor →
07 · Health hazards
Diketene health hazards and exposure limits
Diketene hazard summary
A skin and eye irritant; [CAMEO] Inhalation may cause acute pulmonary edema; [ICSC] Diketene, stabilized (UN2521) has warning of explosive polymerization; [ERG 2016] A severe lachrymator--see Ketene in CAMEO;
Source: Haz-Map, Information on Hazardous Chemicals and Occupational Diseases
08 · Physical and chemical properties
Diketene 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.
Diketene boiling point
| Property | Value | Conditions | Source |
|---|---|---|---|
| Boiling point | 127 °C (260.6 °F) | HSDB | |
| 126.1 °C (259 °F) | at 760 mmHg | DOE PAC |
Diketene melting point
| Property | Value | Conditions | Source |
|---|---|---|---|
| Melting point | -6.5 °C (20.3 °F) | HSDB | |
| -7 °C (19.4 °F) | ICSC |
Diketene density
| Property | Value | Conditions | Source |
|---|---|---|---|
| Density | 1.0877 g/cm³ | at 20 °C | HSDB |
| 1.09 g/cm³ | at 20 °C | ICSC |
Diketene solubility
| Property | Value | Conditions | Source |
|---|---|---|---|
| Solubility | Miscible with most organic solvents. Miscible with hexane | HSDB | |
| Slightly soluble in aliphatic hydrocarbons such as hexane (ca. 12.5 wt% at 23 °C), octane, cyclohexane, and methyl cyclohexane | at 23 °C | HSDB | |
| Very slightly soluble in water in which it decomposes slowly | decomposes | HSDB |
Diketene vapor pressure
| Property | Value | Conditions | Source |
|---|---|---|---|
| Vapor pressure | 8.0257 mmHg | at 20 °C | HSDB |
| 7.5006 mmHg | at 20 °C | ICSC | |
| 10.7 mmHg | at 25 °C | HSDB |
Diketene flash point
| Property | Value | Conditions | Source |
|---|---|---|---|
| Flash point | 34 °C (93.2 °F) | HSDB | |
| 33.89 °C (93 °F) | HSDB |
Diketene autoignition temperature
| Property | Value | Conditions | Source |
|---|---|---|---|
| Autoignition temperature | 310 °C (590 °F) | HSDB | |
| 275 °C (527 °F) | ICSC |
Diketene lower explosive limit (LEL)
| Property | Value | Conditions | Source |
|---|---|---|---|
| Lower explosive limit (LEL) | 2 % by volume | ICSC |
Diketene upper explosive limit (UEL)
| Property | Value | Conditions | Source |
|---|---|---|---|
| Upper explosive limit (UEL) | 11.7 % by volume | ICSC |
Diketene vapor density
| Property | Value | Conditions | Source |
|---|---|---|---|
| Vapor density | 2.9 (air = 1) | HSDB |
Diketene critical temperature and pressure
| Property | Value | Conditions | Source |
|---|---|---|---|
| Critical temperature and pressure | 310 °C (590 °F) | HSDB |
Values compiled from PubChem Laboratory Chemical Safety Summary. Temperatures converted to Fahrenheit for reference.
09 · Fire and explosion
Diketene 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.
Diketene fire potential
Flammable.
Source: Hazardous Substances Data Bank (HSDB)
10 · Handling and storage
Diketene storage and handling
Diketene safe storage
Separated from acids, bases and food and feedstuffs. Well closed. Fireproof. Cool. Dry. Store only if stabilized.
Source: ILO-WHO International Chemical Safety Cards (ICSCs)
Diketene storage conditions
Store at 32 °F (0 °C) in a standard flammable liquids storage warehouse, room, or cabinet. Special vented containers may be required. Separate from oxidizing materials, acids, and alkalies.
Source: Hazardous Substances Data Bank (HSDB)
Diketene incompatible materials
... Can react vigorously with oxidizing materials. A violent polymerization reaction is catalyzed by acids, bases, or sodium acetate.
Source: Hazardous Substances Data Bank (HSDB)
Diketene reactivity
DIKETENE is a very reactive dimer, it may undergo a spontaneous decomposition followed by explosion or ignition [Vervalin, 1973, p.86]. In the presence of bases, amines, mineral acids or Lewis acids a violent polymerization will occur, accompanied by gas evolution [Zdenek, F. et al., Czech Pat. 156 584, 1975].
Source: CAMEO Chemicals
Planning storage for a mix of chemicals? Check Diketene in the storage compatibility matrix →
11 · Transport
Diketene 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.
Diketene under UN 2521 — shipping name, class and packing group
Europe · ADR 2025, Table A
| Proper shipping name (3.1.2) | Class | Classification code | PG | Labels (column 5) |
|---|---|---|---|---|
| DIKETENE, STABILIZED | 6.1 | TF1 | I | |
Source: ADR 2025, Table A of Chapter 3.2 · ECE/TRANS/352 Vol. I (UNECE). Class 6.1 is “Toxic substances” (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) |
|---|---|---|---|
| Diketene, stabilized | 6.1 | I | |
Source: 49 CFR 172.101 Hazardous Materials Table · eCFR, revision 2026-08-03. Class 6.1 is “Poisonous materials” (49 CFR 173.2).
12 · Questions
Diketene — frequently asked questions
What is the CAS number of Diketene?
The CAS number of Diketene is 674-82-8. Its EC number is 211-617-1.
What is the chemical formula of Diketene?
The molecular formula of Diketene is C4H4O2 and its molecular weight is 84.07 g/mol.
What does a Diketene label have to show?
Under CLP Annex VI the label for Diketene carries the pictograms Flame and Exclamation mark and the signal word is Warning.
Is Diketene flammable?
Yes. CLP Annex VI assigns Diketene H226 — flammable liquid and vapour. The flash point reported for it is 34 °C (93.2 °F) (HSDB).
Is Diketene a carcinogen?
CLP Annex VI records no harmonised carcinogenicity classification for Diketene. 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 boiling point of Diketene?
The boiling point reported for Diketene is 127 °C (260.6 °F) (HSDB).
What is the melting point of Diketene?
The melting point reported for Diketene is -6.5 °C (20.3 °F) (HSDB).
How should Diketene be stored?
CLP Annex VI assigns Diketene the storage statement P403. Store at 32 °F (0 °C) in a standard flammable liquids storage warehouse, room, or cabinet. Special vented containers may be required. Separate from oxidizing materials, acids, and alkalies. (Hazardous Substances Data Bank (HSDB))
Nearby
Substances next to Diketene
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