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Bromocresol green

Bromocresol green

Systematic (IUPAC) name
PubChem         6451
Chemical data
Formula C21H14Br4O5S 
Molar mass 698.02
SMILES Cc1c(Br)c(O)c(Br)cc1C2(OS(=O)(=O)
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.

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.

Bromocresol green (pH indicator)
below pH 3.8 above pH 5.4
3.8 5.4


  1. a  PubChem 6451
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Bromocresol_green". A list of authors is available in Wikipedia.
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