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Oil Red O

Athanor · official

C26H24N4O · 408.5 g/mol

IUPAC name: 1-[[4-[(2,5-dimethylphenyl)diazenyl]-2,5-dimethylphenyl]diazenyl]naphthalen-2-ol

Also called solvent red 27, lipid stain, Sudan red 5B

ReagentsRings
Open in Athanor
The structure of Oil Red O
Drawn from its SMILES with RDKit

Names and identifiers

IUPAC name
1-[[4-[(2,5-dimethylphenyl)diazenyl]-2,5-dimethylphenyl]diazenyl]naphthalen-2-ol
Synonyms
solvent red 27, lipid stain, Sudan red 5B
+ 37 more

1-(2-(4-(2-(2,5-Dimethylphenyl)diazenyl)-2,5-dimethylphenyl)diazenyl)-2-naphthalenol, 1-[2-[4-[2-(2,5-Dimethylphenyl)diazenyl]-2,5-dimethylphenyl]diazenyl]-2-naphthalenol, RefChem:223045, Solvent Red 27, 1-((4-((2,5-Dimethylphenyl)diazenyl)-2,5-dimethylphenyl)diazenyl)naphthalen-2-ol, Sudan Red 5B, 1-(2,5-Dimethyl-4-(2,5-dimethylphenylazo)phenylazo)-2-naphthol, C26H24N4O, MFCD00003898, 1-(2-{4-[2-(2,5-dimethylphenyl)diazen-1-yl]-2,5-dimethylphenyl}diazen-1-yl)naphthalen-2-ol, 1-[2,5-Dimethyl-4-(2,5-dimethylphenylazo)phenylazo]-2-naphthol, 1-[[4-[(2,5-dimethylphenyl)diazenyl]-2,5-dimethylphenyl]diazenyl]naphthalen-2-ol, 1-((E)-(4-((E)-(2,5-Dimethylphenyl)diazenyl)-2,5-dimethylphenyl)diazenyl)naphthalen-2-ol, 1-([4-(Xylylazo)xylyl]azo)-2-naphthol, 1-[(4-{Xylylazo}xylyl)azo]-2-naphthol, 1-({4-[(2,5-dimethylphenyl)diazenyl]-2,5-dimethylphenyl}diazenyl)naphthalen-2-ol, EINECS 238-209-6, starbld0000918, C.I. 26125, MolMap_000039, SCHEMBL34877, SCHEMBL630386, SCHEMBL9139615, SCHEMBL11973972, SCHEMBL13070791, SCHEMBL29350896, SCHEMBL31069781, CHEBI:88213, HJAYEODIXUYVIC-LTFAAIOASA-N, NPGIHFRTRXVWOY-UHFFFAOYSA-N, DTXSID301039601, HY-D1168, s4498, 1-[[4-(2,5-dimethylphenyl)azo-2,5-dimethyl-phenyl]hydrazono]naphthalen-2-one, AKOS015903663, FO47172, CI 26125

Molecular formula
C26H24N4O
Empirical formula
C26H24N4O
Molecular weight
408.5 g/mol
Exact mass
408.19501
CAS number
1320-06-5
PubChem CID
2724054
Canonical SMILES
CC1=CC(=C(C=C1)C)N=NC2=C(C=C(C(=C2)C)N=NC3=C(C=CC4=CC=CC=C43)O)C
Isomeric SMILES
CC1=CC(=C(C=C1)C)N=NC2=C(C=C(C(=C2)C)N=NC3=C(C=CC4=CC=CC=C43)O)C
InChI
InChI=1S/C26H24N4O/c1-16-9-10-17(2)22(13-16)27-28-23-14-19(4)24(15-18(23)3)29-30-26-21-8-6-5-7-20(21)11-12-25(26)31/h5-15,31H,1-4H3
InChIKey
NPGIHFRTRXVWOY-UHFFFAOYSA-N
Molfile

Names, InChI and the identifiers from PubChem, retrieved 2026-10-14.

Calculated

Heavy atoms
31
Rings
4
Aromatic rings
4
Fraction sp³ carbons (Fsp3)
0.15
H-bond donors
1
H-bond acceptors
5
Rotatable bonds
4
TPSA (Ų)
69.7
Formal charge
0
XLogP3
7.8 PubChem
Complexity
637 PubChem
Stereocenters
None
Double-bond geometry
N7=N8: E · N16=N17: E
Point group
C1 of one 3D conformer with its hydrogens, by Athanor’s engine (as in the app)

Elemental analysis

  • C76.45%
  • H5.92%
  • N13.72%
  • O3.92%

Isotope pattern

100%408.19530%409.1984.5%410.201411.204

Each peak is a nominal mass with its abundance-weighted exact mass, as a percentage of the tallest, from IUPAC natural isotope abundances.

Computed from the structure with RDKit 2026.09 when this page was built, beside PubChem's own computed values from its record; where the two differ, both are shown.

Predicted

log P
8.61 Crippen (Wildman and Crippen 1999)
log S (water solubility)
-8.06 ESOL (Delaney 2004), log mol/L
Synthetic accessibility
2.8 SA score, 1 easy to 10 hard (Ertl and Schuffenhauer 2009)

Drug-likeness: Lipinski’s rule of five

  • Molecular weight ≤ 500: 408.51
  • log P ≤ 5 (Crippen): 8.61
  • H-bond donors ≤ 5: 1
  • H-bond acceptors ≤ 10: 5

Breaks 1 of the four rules.

¹³C NMR shifts, predicted

Predictions, not measurements; each names its method. A measured log P, where a source reports one, is under Physical properties.

Safety

This chemical does not meet GHS hazard criteria for 100% (2042 of 2042) of all reports.[1]

Safety data sheets on the supplier’s page: Molport, VladaChem, CymitQuimica.

Always read the supplier’s safety data sheet before working with it.

Literature

Reading PubChem, OpenAlex and GSRS…

Bioactivity

Reading ChEMBL…

References

  1. [1]European Chemicals Agency (ECHA) · ECHA legal notice: reuse with acknowledgement · via PubChem · retrieved 2026-10-14
  2. ·Calculated values: computed by Athanor with RDKit 2026.09 from the structure.
  3. ·Literature on PubChem

Data last updated 2026-10-14.