1444. Bromphenol Blue

Nomenclature

CAS number: 115-39-9
4,4′-(1,1-Dioxido-3H-2,1-benzoxathiol-3-ylidene)bis[2,6-dibromophenol]; 4,4′-(3H-2,1-benzoxathiol-3-ylidene)bis[2,6-dibromophenol] S,S-dioxide; α,α-bis(3,5-dibromo-4-hydroxyphenyl)-α-hydroxy-o-toluenesulfonic acid γ-sultone; 3,3′,5,5′-tetrabromophenolsulfonphthalein; bromophenol blue; Albutest (Miles).
C19H10Br4O5S; mol wt 669.96.
C 34.06%, H 1.50%, Br 47.71%, O 11.94%, S 4.79%.

Description and references

Prepd by slow addition of excess bromine to a hot soln of phenolsulfonphthalein in glacial acetic acid: White, Acree, J. Am. Chem. Soc. 41, 1205 (1919); Orndorff, Sherwood, ibid. 45, 495 (1923). See also ref given under Bromcresol Green.

Chemical structure

Properties

Elongated hexagonal prisms from acetic acid + acetone. Dec 279°. (An orange discoloration with formation of a green sublimate sets in at 210°). Soluble in water (about 0.4 g/100 ml); more sol in methyl and ethyl alcohol, and in benzene. Freely sol in NaOH solns with the formation of a water-sol sodium salt. pKa = 4.0. pH 3.0 yellow; pH 4.6 purple. To prepare a soln for use as pH indicator, dissolve 0.10 g in 7.45 ml N/50 NaOH and dil with water to 250 ml.

Derivative

Sodium salt.

Nomenclature

CAS number: 34725-61-6
C19H9Br4NaO5S; mol wt 691.94.
C 32.98%, H 1.31%, Br 46.19%, Na 3.32%, O 11.56%, S 4.63%.

Use

As pH indicator. With mercuric chloride as a semiquantitative protein stain.