Bromothymol blue

Athanor · official

C₂₇H₂₈Br₂O₅S · 624.4 g/mol

IUPAC name: 2-bromo-4-[3-(3-bromo-4-hydroxy-2-methyl-5-propan-2-ylphenyl)-1,1-dioxo-2,1lambda6-benzoxathiol-3-yl]-3-methyl-6-propan-2-ylphenol

Also called BTB, pH indicator, bromthymol blue

Reagents Rings

Open in Athanor

Drawn from its SMILES with RDKit

WarningHarmful if swallowed · Causes skin irritation · Causes serious eye irritation

Names and identifiers

IUPAC name: 2-bromo-4-[3-(3-bromo-4-hydroxy-2-methyl-5-propan-2-ylphenyl)-1,1-dioxo-2,1lambda6-benzoxathiol-3-yl]-3-methyl-6-propan-2-ylphenol
Synonyms: BTB, pH indicator, bromthymol blue
+ 38 more
BROMTHYMOL BLUE, Dibromothymolsulfophthalein, Dibromothymolsulfonphthalein, VGU4LM0H96, DTXSID3058799, NSC7819, NSC-7819, CHEBI:86155, Thymol, 6,6'-(3H-2,1-benzoxathiol-3-ylidene)bis(2-bromo-, S,S-dioxide, Blue, Bromthymol, Blue, Bromothymol, Thymol, 6,6'-(3H-2,1-benzoxathiol-3-ylidene)bis[2-bromo-, S,S-dioxide, RefChem:121663, DTXCID9047831, Phenol, 4,4'-(3H-2,1-benzoxathiol-3-ylidene)bis(2-bromo-3-methyl-6-(1-methylethyl))-, S,S-dioxide, 200-971-2, 4,4'-(3H-2,1-Benzoxathiol-3-ylidene)bis(2-bromo-3-methyl-6-(1-met-hylethyl)phenol) S,S-dioxide, 3,3'-Dibromothymolsulfonphthalein, Bromthymolblau, 3,3-Bis(3-bromo-4-hydroxy-5-isopropyl-2-methylphenyl)-3H-benzo[c][1,2]oxathiole 1,1-dioxide, MFCD00005872, Bromothymol blue (sodium salt), 3',3''-Dibromothymolsulfonphthalein, Phenol,4,4'-(1,1-dioxido-3H-2,1-benzoxathiol-3-ylidene)bis[2-bromo-3-methyl-6-(1-methylethyl)-, 2-bromo-4-[3-(3-bromo-4-hydroxy-2-methyl-5-propan-2-ylphenyl)-1,1-dioxo-2,1lambda6-benzoxathiol-3-yl]-3-methyl-6-propan-2-ylphenol, Phenol, 4,4'-(1,1-dioxido-3H-2,1-benzoxathiol-3-ylidene)bis(2-bromo-3-methyl-6-(1-methylethyl)-, Phenol, 4,4'-(3H-2,1-benzoxathiol-3-ylidene)bis(2-bromo-3-methyl-6-(1-methylethyl)-, S,S-dioxide, 3,3-bis[3-bromo-4-hydroxy-2-methyl-5-(propan-2-yl)phenyl]-3H-2,1??-benzoxathiole-1,1-dione, Phenol, 4,4'-(3H-2,1-benzoxathiol-3-ylidene)bis[2-bromo-3-methyl-6-(1-methylethyl)-, S,S-dioxide, C27H28Br2O5S, NSC 7819, EINECS 200-971-2, UNII-VGU4LM0H96, BRN 0373934, Dibromothymolsulfophthalein; 3,3'-Dibromothymolsulfonphthalein, Azul de bromotimol, Blu di bromotimolo, 3,3-bis[3-bromo-4-hydroxy-2-methyl-5-(methylethyl)phenyl]benzo[c]1,2-oxathiole ne-1,1-dione
Molecular formula: C₂₇H₂₈Br₂O₅S
Empirical formula: C₂₇H₂₈Br₂O₅S
Molecular weight: 624.4 g/mol
Exact mass: 624.00037
CAS number: 76-59-5
PubChem CID: 6450
Canonical SMILES: CC1=C(C=C(C(=C1Br)O)C(C)C)C2(C3=CC=CC=C3S(=O)(=O)O2)C4=C(C(=C(C(=C4)C(C)C)O)Br)C
Isomeric SMILES: CC1=C(C=C(C(=C1Br)O)C(C)C)C2(C3=CC=CC=C3S(=O)(=O)O2)C4=C(C(=C(C(=C4)C(C)C)O)Br)C
InChI: InChI=1S/C27H28Br2O5S/c1-13(2)17-11-20(15(5)23(28)25(17)30)27(19-9-7-8-10-22(19)35(32,33)34-27)21-12-18(14(3)4)26(31)24(29)16(21)6/h7-14,30-31H,1-6H3
InChIKey: NUHCTOLBWMJMLX-UHFFFAOYSA-N
Molfile

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

Calculated

Heavy atoms: 35
Rings: 4
Aromatic rings: 3
Fraction sp³ carbons (Fsp3): 0.33
H-bond donors: 2
H-bond acceptors: 5
Rotatable bonds: 4
TPSA (Å²): 83.8 computed here · PubChem 92.2
Formal charge: 0
XLogP3: 7.6 PubChem
Complexity: 818 PubChem
Stereocenters: 0 defined, 1 undefinedCIP: C13: undefined
Double-bond geometry: None specified
Point group: C1 of one 3D conformer with its hydrogens, by Athanor’s engine (as in the app)

Elemental analysis

C51.94%
H4.52%
Br25.59%
O12.81%
S5.14%

Isotope pattern

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: 7.5 Crippen (Wildman and Crippen 1999)
log S (water solubility): -8.55 ESOL (Delaney 2004), log mol/L
Synthetic accessibility: 3.99 SA score, 1 easy to 10 hard (Ertl and Schuffenhauer 2009)

Drug-likeness: Lipinski’s rule of five

Molecular weight ≤ 500: 624.39
log P ≤ 5 (Crippen): 7.5
H-bond donors ≤ 5: 2
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

Warning

Most widely reported: 9 company reports to ECHA. Source [1].

Harmful or irritant

H302Harmful if swallowed (11.1% of reports)
H315Causes skin irritation (11.1% of reports)
H319Causes serious eye irritation (11.1% of reports)

Precautionary statements: P264, P264+P265, P270, P280, P301+P317, P302+P352, P305+P351+P338, P321, P330, P332+P317, P337+P317, P362+P364, P501

View all classifications (2)

[1] European Chemicals Agency (ECHA)This chemical does not meet GHS hazard criteria for 77.8% (7 of 9) of all reports.
[1] European Chemicals Agency (ECHA) · 9 reports · WarningH302, H315, H319

Safety data sheets on the supplier’s page: MedChemexpress MCE, GSP Chem Ind, LGC Standards.

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

Spectra

Experimental spectra held by these sources; each link opens the source's own record.

Literature

Reading PubChem, OpenAlex and GSRS…

Bioactivity

Reading ChEMBL…

References

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

Data last updated 2026-10-14.