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Annex II Entry 1138 CMR15/10/2010

Isoprene (stabilized); (2-Methyl-1,3-butadiene)

Isoprene (stabilized); (2-Methyl-1,3-butadiene) is listed in Annex II as a prohibited substance for cosmetic products placed on the EU market.

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Prohibited substance— Annex II, EU Regulation 1223/2009
Entry: 1138
CMR

Chemical identity and properties

PubChem 2D chemical structure for CAS 78-79-5
CAS 78-79-5PubChem CID 6557

Isoprene

Isoprene is a hemiterpene with the formula CH2=C(CH3)CH=CH2; the monomer of natural rubber and a common structure motif to the isoprenoids, a large class of other naturally occurring compounds. It has a role as a plant metabolite. It is a volatile organic compound, an alkadiene and a hemiterpene. — ChEBI

IUPAC name
2-methylbuta-1,3-diene
Molecular formula
C5H8
Molecular weight
68.12 g/mol
Exact mass
68.062600255 Da
XLogP3
2.5
Topological polar surface area
0.0 Ų
Hydrogen-bond donors
0
Hydrogen-bond acceptors
0
Covalent units
1
Defined stereocentres
0

Also known as

2-Methyl-1,3-butadieneIsopentadiene2-Methylbutadiene2-Methyldivinyl1,3-Butadiene, 2-methyl-beta-Methylbivinyl3-Methyl-1,3-butadiene0A62964IBU
16 more reported names
NSC-9237CHEBI:35194NSC9237Methyl bivinylRefChem:5919201-143-3NATURAL RUBBERisoprenoisoterpeneIsoprenRubber, natural.beta.-Methylbivinyl9006-04-6CH2=C(CH3)CH=CH2NSC 9237Isoprene (Stabilized with TBC)
Open full PubChem recordPubChem annotations3D structure image
External database identifiers

Retrieved from NIH PubChem on 2026-08-31 by checksum-valid CAS matching. Chemical properties do not replace the regulatory decision on this page.

Record details

Chemical name

Isoprene (stabilized); (2-Methyl-1,3-butadiene)

Regulatory information

Regulation

(EC) 2009/1223

See every entry this act set

SCCS opinions

CMR

CategoryCarcinogenicMutagenicReprotoxic
Cat. 1B✓——
Cat. 2—✓—

Key data

CAS
78-79-5
EC
201-143-3
Annex
II
Entry number
1138

Direct matches are limited for this record, so nearby entries from Annex II are shown as well.

Annex II 1137
Nearby record in the same annex

Isobutyl nitrite

CAS: 542-56-3
EC: 208-819-7
Annex II 1143
Nearby record in the same annex

Dinocap (ISO)

CAS: 39300-45-3
EC: 254-408-0

What Annex II means for Isoprene (stabilized); (2-Methyl-1,3-butadiene)

Isoprene (stabilized); (2-Methyl-1,3-butadiene) is listed as a prohibited substance under Annex II of EU Cosmetics Regulation 1223/2009 and must not be intentionally added. Article 17 separately addresses unintended small quantities that are technically unavoidable under good manufacturing practice and compatible with the Article 3 safety requirement.

Formulators must screen their ingredients and raw materials to ensure none contain this substance. Suppliers should provide documentation confirming absence when requested.

The page also surfaces 12 related annex records with overlapping identifiers, annex logic or naming patterns.

Compliance checklist

  • Verify this substance is absent from all raw materials and finished formulations.
  • Request absence confirmation or CoA from raw material suppliers.
  • Document the screening result in the Product Information File (PIF).
  • This substance has CMR classification. Review the CMR table above and verify current Annex II/III status before use.

Frequently asked questions

Yes. Isoprene (stabilized); (2-Methyl-1,3-butadiene) is listed in Annex II of EU Cosmetics Regulation 1223/2009 and is prohibited as an intentionally added cosmetic ingredient. Article 17 provides a narrow exception for unintended small quantities that are technically unavoidable under good manufacturing practice, provided the product remains safe under Article 3.

CAS 78-79-5 is the unique numerical identifier assigned to Isoprene (stabilized); (2-Methyl-1,3-butadiene) by the Chemical Abstracts Service. In cosmetic compliance work, the CAS number is used to cross-reference the substance across regulatory databases, raw material specifications and safety assessment reports. Multiple EU annex entries may share the same CAS number if the same substance appears under different conditions or in different annexes.

Isoprene (stabilized); (2-Methyl-1,3-butadiene) has a CMR (carcinogenic, mutagenic or reprotoxic) classification under EU CLP Regulation. Under Article 15 of EU Cosmetics Regulation 1223/2009, CMR substances of category 1A or 1B are prohibited in cosmetics unless specifically permitted. Category 2 CMR substances may be used only if assessed safe by the SCCS. Always verify current annex status and any applicable derogations before use.

Use the INCI Checker tool on this site to paste your full ingredient list (INCI) and scan it against all Annex II–VI entries. The tool highlights any ingredients that match restricted, prohibited or allergen-flagged records. This is useful for rapid compliance screening of finished product formulas or raw material declarations.
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Source note for Annex II record Isoprene (stabilized); (2-Methyl-1,3-butadiene)

This page summarizes one Annex II record for Isoprene (stabilized); (2-Methyl-1,3-butadiene) from public European Commission cosmetic materials and adds linked inventory or identifier matches when available.

Use this record page to review Annex II conditions for Isoprene (stabilized); (2-Methyl-1,3-butadiene), but confirm any final regulatory decision against the current official annex wording and source files.

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