Substance profile
Isoprene
Isoprene is a colorless volatile liquid with a petroleum-lke odor.
01 · Identification
What Isoprene is
Isoprene is a colorless volatile liquid with a petroleum-lke odor. Its molecular formula is C5H8 and its molecular weight is 68.12 g/mol. It boils at 34.1 °C, melts at -146 °C.
Under the GHS it carries the signal word Danger. It is classed as carcinogens.
02 · Identifiers
Isoprene identifiers and molecular data
Isoprene CAS number and EC number
Isoprene molecular formula and molecular weight
Other names for Isoprene
- isoprene (stabilised)
- 2-methyl-1,3-butadiene
03 · GHS classification
Isoprene hazard classification
Harmonised classification under CLP Annex VI. This is the legally binding classification in the EU; other jurisdictions may differ.
Isoprene pictograms and signal word
Isoprene hazard class and category
| Hazard class | Category | From code | Pictogram |
|---|---|---|---|
| Flammable liquids GHS chapter 2.6 | Category 1 | H224 | GHS02 |
| Germ cell mutagenicity GHS chapter 3.5 | Category 2 | H341 | GHS08 |
| Carcinogenicity GHS chapter 3.6 | Category 1A or 1B | H350 | GHS08 |
| Hazardous to the aquatic environment - chronic GHS chapter 4.1 | Category 3 | H412 | — |
Where two values are shown with “or”, the hazard statement is shared by more than one category or by more than one class, and the code alone does not say which. H272, for example, belongs to oxidising liquids and to oxidising solids — the physical state decides. The binding answer for a specific entry is in the CLP Annex VI table itself.
Isoprene hazard statements (H-codes)
| Code | Hazard statement |
|---|---|
| H224 | Extremely flammable liquid and vapour. |
| H350 | May cause cancer <state route of exposure if it is conclusively proven that no other routes of exposure cause the hazard>. |
| H341 | Suspected of causing genetic defects <state route of exposure if it is conclusively proven that no other routes of exposure cause the hazard>. |
| H412 | Harmful to aquatic life with long lasting effects. |
This page lists only the codes assigned to Isoprene. 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 Isoprene
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 Isoprene 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
Isoprene precautionary statements
CLP Annex VI assigns 11 precautionary statements to Isoprene. 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.
Disposal
What has to happen to the contents and the empty container.
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
Isoprene 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 | изопрен (стабилизиран) 2-метил-1,3-бутадиен |
| Spanish español | Isopreno (estabilizado) 2-metil-1,3-butadieno |
| Czech čeština | isopren (stabilizovaný) 2-methylbuta-1,3-dien |
| Danish dansk | isopren (stabiliseret) 2-methyl-1,3-butadien |
| German Deutsch | Isopren (stabilisiert) 2-Methyl-1,3-butadien |
| Estonian eesti | isopreen (stabiliseeritud) 2-metüül-1,3-butadieen |
| Greek ελληνικά | ισοπρένιο (σταθεροποιημένο) 2-μεθυλο-1,3-βουταδιένιο |
| English English | isoprene (stabilised) 2-methyl-1,3-butadiene |
| French français | isoprène (stabilisé) 2-méthyl-1,3-butadiène |
| Croatian hrvatski | izopren (stabilizirani) 2-metil-1,3-butadien |
| Italian italiano | isoprene (stabilizzato) 2-metil-1,3-butadiene |
| Latvian latviešu | izoprēns (stabilizēts) 2-metil-1,3-butadiēns |
| Lithuanian lietuvių | izoprenas (stabilizuotas) 2-metil-1,3-butadienas |
| Hungarian magyar | izoprén (stabilizált) 2-metil-1,3-butadién |
| Maltese Malti | isopren (stabbilizzat) 2-metil-1,3-butadjen |
| Dutch Nederlands | isopreen (gestabiliseerd) 2-methyl-1,3-butadieen |
| Polish polski | izopren (stabilizowany) 2-metylo-1,3-butadien |
| Portuguese português | isopreno (estabilizado) 2-metil-1,3-butadieno |
| Romanian română | izopren (stabilizat) 2-metil-1,3-butadienă |
| Slovak slovenčina | izoprén (stabilizovaný) 2-metylbuta-1,3-dién |
| Slovenian slovenščina | izopren (stabiliziran) 2-metil-1,3-butadien |
| Finnish suomi | isopreeni (stabiloitu) 2-metyyli-1,3-butadieeni |
| Swedish svenska | isopren (stabiliserad) 2-metyl-1,3-butadien |
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
Isoprene GHS label elements
Everything CLP Annex VI fixes for Isoprene, laid out the way it appears on a label. The greyed lines are the parts only the supplier can fill in.
Danger
Isoprene
- Extremely flammable liquid and vapour.
- May cause cancer <state route of exposure if it is conclusively proven that no other routes of exposure cause the hazard>.
- Suspected of causing genetic defects <state route of exposure if it is conclusively proven that no other routes of exposure cause the hazard>.
- Harmful to aquatic life with long lasting effects.
- Obtain special instructions before use.
- 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.
- Avoid release to the environment.
- Wear protective gloves/protective clothing/eye protection/face protection/hearing protection/…
- IF exposed or concerned:
- Get medical advice/attention.
- Store in a well-ventilated place.
- Dispose of contents/container to …
Supplier name, address and telephone number· Product identifier·Nominal quantity
Need this as an actual label? Open Isoprene in the GHS label constructor →
07 · Health hazards
Isoprene health hazards and exposure limits
Isoprene hazard summary
An irritant to the skin, eyes, and mucous membranes; Causes CNS depression at high concentrations; [HSDB] If left on clothes, may cause reddening of skin; [CHRIS] Can affect the CNS, resulting in respiratory depression; [ICSC] Human volunteers complain of slight upper respiratory tract irritation when exposed to 57 ppm; [AIHA] Isoprene, stabilized (UN1218) has warning of explosive polymerization; [ERG 2016]
Source: Haz-Map, Information on Hazardous Chemicals and Occupational Diseases
Isoprene carcinogenicity classification
Under the conditions of this 2-year inhalation study, there was clear evidence of carcinogenic activity of isoprene in male F344/N rats based on increased incidences of mammary gland fibroadenoma and carcinoma, renal tubule adenoma, and testicular interstitial cell adenoma. There was some evidence of carcinogenic activity of isoprene in female F344/N rats based on increased incidences and multiplicity of mammary gland fibroadenoma. A low incidence of rare brain neoplasms in exposed female rats may have been due to exposure to isoprene.
Source: US National Toxicology Program · TR-486: Toxicology and Carcinogenesis Studies of Isoprene (CASRN 78-79-5) in F344/N Rats (Inhalation Studies) (1999 )
Evaluation: No epidemiological data relevant to the carcinogenicity of isoprene were available. There is sufficient evidence in experimental animals for the carcinogenicity of isoprene. Overall evaluation: Isoprene is possibly carcinogenic to humans (Group 2B).
Source: Hazardous Substances Data Bank (HSDB)
Isoprene is reasonably anticipated to be a human carcinogen
Source: Hazardous Substances Data Bank (HSDB)
An IARC group and a CLP classification answer different questions. IARC judges whether the evidence for cancer in humans is strong enough; CLP Annex VI is the legally binding EU classification. A substance can carry one and not the other.
08 · Physical and chemical properties
Isoprene 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.
Isoprene boiling point
| Property | Value | Conditions | Source |
|---|---|---|---|
| Boiling point | 34.07 °C (93.3 °F) | HSDB | |
| 33.89 °C (93 °F) | at 760 mmHg | CAMEO | |
| 34 °C (93.2 °F) | ICSC |
Isoprene melting point
| Property | Value | Conditions | Source |
|---|---|---|---|
| Melting point | -145.95 °C (-230.7 °F) | HSDB | |
| 30 °C (86 °F) | HSDB | ||
| -120 °C (-184 °F) | CAMEO |
Isoprene density
| Property | Value | Conditions | Source |
|---|---|---|---|
| Density | 0.7 g/cm³ | ICSC | |
| 0.679 g/cm³ | at 20 °C | HSDB | |
| 0.681 g/cm³ | at 20 °C | CAMEO |
Isoprene solubility
| Property | Value | Conditions | Source |
|---|---|---|---|
| Solubility | Practically insoluble in water | HSDB | |
| Miscible with ethanol, ethyl ether, acetone, benzene | HSDB | ||
| In water, 642 mg/L at 25 °C | at 25 °C | HSDB |
Isoprene vapor pressure
| Property | Value | Conditions | Source |
|---|---|---|---|
| Vapor pressure | 399.033 mmHg | at 20 °C | ICSC |
| 550 mmHg | at 25 °C | HSDB | |
| 400 mmHg | at 15.4 °C | HSDB |
Isoprene flash point
| Property | Value | Conditions | Source |
|---|---|---|---|
| Flash point | -53.89 °C (-65 °F) | HSDB |
Isoprene autoignition temperature
| Property | Value | Conditions | Source |
|---|---|---|---|
| Autoignition temperature | 395 °C (743 °F) | HSDB | |
| 220 °C (428 °F) | ICSC |
Isoprene lower explosive limit (LEL)
| Property | Value | Conditions | Source |
|---|---|---|---|
| Lower explosive limit (LEL) | 1.5 % by volume | HSDB | |
| 1 % by volume | HSDB | ||
| 2 % by volume | CAMEO |
Isoprene upper explosive limit (UEL)
| Property | Value | Conditions | Source |
|---|---|---|---|
| Upper explosive limit (UEL) | 8.9 % by volume | HSDB | |
| 9.7 % by volume | HSDB |
Isoprene vapor density
| Property | Value | Conditions | Source |
|---|---|---|---|
| Vapor density | 2.35 (air = 1) | HSDB | |
| 2.4 (air = 1) | ICSC |
Isoprene critical temperature and pressure
| Property | Value | Conditions | Source |
|---|---|---|---|
| Critical temperature and pressure | 211.11 °C (412 °F) | HSDB |
Values compiled from PubChem Laboratory Chemical Safety Summary. Temperatures converted to Fahrenheit for reference.
09 · Fire and explosion
Isoprene 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.
Isoprene fire potential
Extremely flammable.
Source: Hazardous Substances Data Bank (HSDB)
10 · Handling and storage
Isoprene storage and handling
Isoprene safe storage
Fireproof. Separated from combustible substances, reducing agents, strong oxidants, strong bases, strong acids, alcohols and acid chlorides. Cool. Keep in the dark. Well closed. Store only if stabilized. Provision to contain effluent from fire extinguishing. Store in an area without drain or sewer access.
Source: ILO-WHO International Chemical Safety Cards (ICSCs)
Isoprene storage conditions
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.
Source: Hazardous Substances Data Bank (HSDB)
Isoprene incompatible materials
Mixing isoprene and chlorosulfonic acid in a closed container caused the temperature and pressure to increase.
Source: Hazardous Substances Data Bank (HSDB)
Isoprene reactivity
ISOPRENE may react vigorously with strong oxidizing agents. May react exothemically with reducing agents to release hydrogen gas. May undergo exothermic addition polymerization in the presence of various catalysts (such as acids) or initiators. Undergoes autoxidation upon exposure to the air to form explosive peroxides. Mixing isoprene in equal molar portions with any of the following substances in a closed container caused the temperature and pressure to increase: chlorosulfonic acid, nitric acid (70%), oleum, sulfuric acid (90%) [NFPA 1991].
Source: CAMEO Chemicals
Planning storage for a mix of chemicals? Check Isoprene in the storage compatibility matrix →
11 · Transport
Isoprene 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.
Isoprene under UN 1218 — shipping name, class and packing group
Europe · ADR 2025, Table A
| Proper shipping name (3.1.2) | Class | Classification code | PG | Labels (column 5) |
|---|---|---|---|---|
| ISOPRENE, STABILIZED | 3 | F1 | I | |
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) |
|---|---|---|---|
| Isoprene, stabilized | 3 | I | |
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
Isoprene — frequently asked questions
What is the CAS number of Isoprene?
The CAS number of Isoprene is 78-79-5. Its EC number is 201-143-3.
What is the chemical formula of Isoprene?
The molecular formula of Isoprene is C5H8 and its molecular weight is 68.12 g/mol.
What does a Isoprene label have to show?
Under CLP Annex VI the label for Isoprene carries the pictograms Flame and Health hazard and the signal word is Danger.
Is Isoprene flammable?
Yes. CLP Annex VI assigns Isoprene H224 — extremely flammable liquid and vapour. The flash point reported for it is -53.89 °C (-65 °F) (HSDB).
Is Isoprene a carcinogen?
Yes. CLP Annex VI classifies Isoprene as a category 1A or 1B carcinogen and assigns it H350: may cause cancer. IARC places it in Group 2B: possibly carcinogenic to humans.
What is the boiling point of Isoprene?
The boiling point reported for Isoprene is 34.07 °C (93.3 °F) (HSDB).
What is the melting point of Isoprene?
The melting point reported for Isoprene is -145.95 °C (-230.7 °F) (HSDB).
How should Isoprene be stored?
CLP Annex VI assigns Isoprene the storage statement P403. 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. (Hazardous Substances Data Bank (HSDB))
Nearby
Substances next to Isoprene
Keep going: substances starting with I, or search the whole database by name, CAS number, pictogram or signal word.