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Bromocresol green


Bromocresol green
Systematic (IUPAC) name
2,6-dibromo-4-[7-(3,5-dibromo-4-hydroxy-2-methyl- phenyl)-9,9-dioxo-8-oxa-9λ6-thiabicyclo[4.3.0]nona- 1,3,5-trien-7-yl]-3-methyl-phenol
Identifiers
PubChem	6451
Chemical data
Formula	C₂₁H₁₄Br₄O₅S
Molar mass	698.02
SMILES	Cc1c(Br)c(O)c(Br)cc1C2(OS(=O)(=O) c3ccccc23)c4cc(Br)c(O)c(Br)c4C
Complete data

Bromocresol green (3,3',5,5'-tetrabromo-m-cresolsulfonphthalein) is a dye of the triphenylmethane family (triarylmethane dyes), which is used as a pH indicator and as a tracking dye for DNA agarose gel electrophoresis. It can be used in its free acid form (light brown solid), or as a sodium salt (dark green solid). It is also an inhibitor of the prostaglandin E₂ transport protein.

Additional recommended knowledge

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Daily Sensitivity Test

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In aqueous solution, both solids ionize to give the monoanionic form (yellow), that further deprotonates at higher pH to give the dianionic form (blue), which is stabilized by resonance:

The pK (pKa) of this reaction is 4.9.

The acid and basic form of this dye have an isosbestic point in their spectra, around 515 nm.