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CAS 2 records

CAS 2051-85-6

CAS 2051-85-6 matches 2 EU annex records across Annex II–VI of Regulation 1223/2009.

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Chemical identity and properties

PubChem 2D chemical structure for CAS 2051-85-6
CAS 2051-85-6PubChem CID 16325

4-(Phenylazo)resorcinol

IUPAC name
4-phenyldiazenylbenzene-1,3-diol
Molecular formula
C12H10N2O2
Molecular weight
214.22 g/mol
Exact mass
214.074227566 Da
XLogP3
3.0
Topological polar surface area
65.2 Ų
Hydrogen-bond donors
2
Hydrogen-bond acceptors
4
Covalent units
1
Defined stereocentres
0

Also known as

2,4-Dihydroxyazobenzene1,3-Benzenediol, 4-(phenylazo)-1,3-Benzenediol, 4-(2-phenyldiazenyl)-RefChem:516611Sudan Orange GSolvent orange 1Ceres Orange GCeres Orange GN
16 more reported names
Sudan GFat Orange ABenzeneazoresorcinolC.I. Solvent Orange 1Sudan Yellow ARResinol Orange GFat Orange GSFat Orange RGCerisol Yellow GRGrasol Yellow RSFOrganol Orange 2JTertrogras Orange SGFat Victoria Yellow D1504 YellowC.I. Food Orange 3p-Phenylazoresorcinol
Open full PubChem recordPubChem annotations3D structure image
External database identifiers

Retrieved from NIH PubChem on 2026-09-02 by checksum-valid CAS matching. Chemical properties do not replace the regulatory decision on this page.

Records for CAS 2051-85-6

2 total

How CAS 2051-85-6 is used on this site

CAS 2051-85-6 is the Chemical Abstracts Service identifier used to pin this page to a specific substance. In the current dataset, 2 EU annex records share 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 2051-85-6 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 2051-85-6 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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