Catechol phthalein

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Structural formula
Structural formula of pyrocatecholphthalein
General
Surname Catechol phthalein
other names
  • 3,3-bis (3,4-dihydroxyphenyl) -2-benzofuran-1 (3 H ) -one ( IUPAC )
  • 3-oxo-1,1-bis (3,4-dihydroxyphenyl) phthalate
  • Pyrocatecholphthalein
  • Phthalein Violet
Molecular formula C 20 H 14 O 6
External identifiers / databases
CAS number 596-28-1
PubChem 68996
ChemSpider 62218
Wikidata Q65926506
properties
Molar mass 350.3 g mol −1
Physical state

firmly

safety instructions
GHS hazard labeling
no classification available
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Catecholphthalein is a dye belonging to the phthalein class . The compound was first synthesized in 1889 by Adolf von Baeyer and Ernst Kochendoerfer from phthalic anhydride and catechol .

properties

A solution of catechol phthalein is pale yellow in the pH range 6–6.5, purple in the pH range 8–10 and blue in the pH range 11–13:

Indicator reaction of pyrocatecholphthalein at different pH values

use

Catecholphthalein dissolved in ammonia can be used in chelatometry as an indicator for the photometric determination of various metal ions (e.g. aluminum , boron , calcium , magnesium , copper , cobalt , nickel ). The violet solution in the pH range 8-10.5 ( absorption maximum at 595 nm) changes its color to blue-green in the presence of metal ions.

Individual evidence

  1. ↑ This substance has either not yet been classified with regard to its hazardousness or a reliable and citable source has not yet been found.
  2. ^ Adolf Baeyer, Ernst Kochendoerfer: Ueber das Phtaleïn des pyrocatechins . In: Reports of the German Chemical Society . tape 22 , no. 2 , July 1889, p. 2196-2200 , doi : 10.1002 / cber.18890220288 .
  3. ^ Richard Meyer, Hermann Pfotenhauer: About the catecholphthalein . In: Reports of the German Chemical Society . tape 40 , no. 2 , March 1907, p. 1442-1445 , doi : 10.1002 / cber.19070400228 .
  4. ↑ a b V. Patrovsky: Phthaleinviolett as indicator in the chelatometry . In: Fresenius' Journal for Analytical Chemistry . tape 214 , no. 5 , September 1965, p. 321-324 , doi : 10.1007 / BF00511511 .