Why does CAS 591-78-6 appear in more than one EU cosmetic annex?

A substance identified by CAS 591-78-6 may appear in multiple EU cosmetic regulation annexes when it is subject to different conditions in different contexts — for example, restricted under Annex III with specific conditions, while also appearing in Annex IV as an approved colorant under separate entry conditions. Each entry must be reviewed individually.

How do I check if my formula contains a substance with CAS 591-78-6?

Use the INCI Checker on CosIng Checker with INCI names, CAS numbers or EC numbers. Paste CAS 591-78-6 to screen it directly, then review every linked annex record and supplier document.

CAS 1 record

CAS 591-78-6

Q: How do I use CAS 591-78-6 for compliance screening?

Cross-reference CAS 591-78-6 against your raw material specification sheets and CoA documents. When it appears in Annex II, verify absence. When it appears in Annex III, verify that concentration limits and product type conditions are met. All annex entries sharing this CAS number are listed on this page.

CAS 591-78-6 matches 1 EU annex record across Annex II–VI of Regulation 1223/2009.

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Chemical identity and properties

PubChem 2D chemical structure for CAS 591-78-6

CAS 591-78-6PubChem CID 11583

2-Hexanone

2-Oxohexane is a ketone. — ChEBI

IUPAC name: hexan-2-one

Molecular formula: C6H12O
Molecular weight: 100.16 g/mol
Exact mass: 100.088815002 Da
XLogP3: 1.4
Topological polar surface area: 17.1 Å²
Hydrogen-bond donors: 0
Hydrogen-bond acceptors: 1
Covalent units: 1
Defined stereocentres: 0

Also known as

Butyl methyl ketoneMethyl butyl ketone2-OxohexanePropylacetoneMethyl N-butyl ketonen-Butyl methyl ketoneHexanone-2MNBK

16 more reported names

Ketone, butyl methylmethyl-n-butyl ketone6QDY60NH6NButylmethyl Ketone2 HexanoneHexan 2 oneKetone, ButylmethylMethyl n Butyl KetoneKetone, Methyl n-Butyln-Butyl Ketone, MethylRefChem:472860209-731-12-Hexanone Methyl n-butyl ketonen-C4H9COCH3Sodium Valproate Impurity Omethylbutyl ketone

Open full PubChem record PubChem annotations 3D structure image

External database identifiers

ChEBI:CHEBI:89206
ChEMBL:CHEMBL195861
EPA DTXSID:DTXSID0022068
PubMed:23090075
PubMed:23071601
PubMed:23029348
PubMed:23021245
PubMed:22956755
PubMed:22939182
PubMed:22929552
PubMed:22880092
PubMed:22848478
PubMed:22814699
PubMed:22814149
PubMed:22754652

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

Records for CAS 591-78-6

1 total

Annex

Entry

1074

Hexan-2-one (Methyl butyl ketone)

209-731-1

CMR

How CAS 591-78-6 is used on this site

CAS 591-78-6 is the Chemical Abstracts Service identifier used to pin this page to a specific substance. In the current dataset, 1 EU annex record shares this identifier, which helps you cross-check whether the same substance appears under one regulatory context or several.

Use this page when a supplier specification, SDS or raw-material dossier gives you CAS 591-78-6 and you need to see every linked Annex II–VI record in one place. The entry cards above are the quickest route to concentration limits, warnings, annex placement and product-type conditions.

Frequently asked questions

A substance identified by CAS 591-78-6 may appear in multiple EU cosmetic regulation annexes when it is subject to different conditions in different contexts. For example, a substance might be restricted under Annex III with specific conditions, and the same CAS might also appear in Annex IV as an approved colorant under separate entry conditions. Each entry must be reviewed individually.

Cross-reference the CAS number against your raw material specification sheets and CoA documents. When a CAS appears in Annex II, verify absence. When it appears in Annex III, verify that concentration limits and product type conditions are met in your formulation. All annex entries sharing this CAS number are listed above.

A CAS number is assigned by the Chemical Abstracts Service (USA) and is globally recognised. An EC number is a European Commission identifier from inventories such as EINECS, ELINCS or the NLP list. Both identifiers may appear in EU cosmetic annex entries. Some substances have both, some have only one, and some older entries may have neither.

The INCI Checker accepts ingredient names, CAS numbers and EC numbers. Check this CAS number directly, then verify the result against supplier specification sheets and every linked annex condition.

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Tools & next steps

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