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Eosin Y

Athanor · official

C20H6Br4O5-2 · 645.9 g/mol

IUPAC name: 2',4',5',7'-tetrabromo-3-oxospiro[2-benzofuran-1,9'-xanthene]-3',6'-diolate

Also called acid red 87, H&E stain, eosin, bromofluorescein

ReagentsRings
Open in Athanor
The structure of Eosin Y
Drawn from its SMILES with RDKit

Names and identifiers

IUPAC name
2',4',5',7'-tetrabromo-3-oxospiro[2-benzofuran-1,9'-xanthene]-3',6'-diolate
Synonyms
acid red 87, H&E stain, eosin
+ 1 more

bromofluorescein

Molecular formula
C20H6Br4O5-2
Empirical formula
C20H6Br4O5
Molecular weight
645.9 g/mol
Exact mass
645.69077
CAS number
17372-87-1
PubChem CID
4677702
Canonical SMILES
C1=CC=C2C(=C1)C(=O)OC23C4=CC(=C(C(=C4OC5=C(C(=C(C=C35)Br)[O-])Br)Br)[O-])Br
Isomeric SMILES
C1=CC=C2C(=C1)C(=O)OC23C4=CC(=C(C(=C4OC5=C(C(=C(C=C35)Br)[O-])Br)Br)[O-])Br
InChI
InChI=1S/C20H8Br4O5/c21-11-5-9-17(13(23)15(11)25)28-18-10(6-12(22)16(26)14(18)24)20(9)8-4-2-1-3-7(8)19(27)29-20/h1-6,25-26H/p-2
InChIKey
DBZJJPROPLPMSN-UHFFFAOYSA-L
Molfile

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

Calculated

Heavy atoms
29
Rings
5
Aromatic rings
3
Fraction sp³ carbons (Fsp3)
0.05
H-bond donors
0
H-bond acceptors
5
Rotatable bonds
0
TPSA (Ų)
81.7
Formal charge
-2
XLogP3
7.5 PubChem
Complexity
645 PubChem
Stereocenters
None
Double-bond geometry
None specified
Point group
Cs of one 3D conformer with its hydrogens, by Athanor’s engine (as in the app)

Elemental analysis

  • C37.19%
  • H0.94%
  • Br49.49%
  • O12.39%

Isotope pattern

17%641.6953.8%642.69868%643.69315%644.696100%645.69122%646.69467%647.68914%648.69218%649.6883.6%650.691651.693

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
5.45 Crippen (Wildman and Crippen 1999)
log S (water solubility)
-7.74 ESOL (Delaney 2004), log mol/L
Synthetic accessibility
4.25 SA score, 1 easy to 10 hard (Ertl and Schuffenhauer 2009)

Drug-likeness: Lipinski’s rule of five

  • Molecular weight ≤ 500: 645.88
  • log P ≤ 5 (Crippen): 5.45
  • H-bond donors ≤ 5: 0
  • H-bond acceptors ≤ 10: 5

Breaks 2 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

No GHS hazard classification was found in the sources.

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

Literature

Reading PubChem, OpenAlex and GSRS…

Bioactivity

Reading ChEMBL…

References

  1. ·Calculated values: computed by Athanor with RDKit 2026.09 from the structure.
  2. ·Literature on PubChem

Data last updated 2026-10-14.