Xanthene dyes
Xanthene dyes are a class of organic dyes derived from the heterocyclic compound xanthene . By introducing electron-donating substituents (so-called auxochromes ) on the aromatic rings, a quinoid system can form as a chromophore , which determines the color of the compounds. Xanthene dyes with a phenyl substituent on the pyran ring also belong to the group of triphenylmethane dyes . The superordinate group of dyes are the methine dyes . The cationic xanthene dyes are also known as pyronines .
π-electron systems of xanthene (left) and xanthene dyes (right). X can be oxygen (hydroxyl or oxo group) or nitrogen (amino / imino group).
The xanthene dyes include eosin B , eosin Y , fluorescein , pyronin G and the rhodamines .
Manufacturing
The dyes were used in research into the reactions of substituted phenols with carbonyl compounds, e.g. B. aldehydes or dicarboxylic anhydrides discovered. The reaction with aldehydes sometimes produces a colorless intermediate, which was called the “leuco compound” (Greek leukos = white). This then has to be oxidized or dehydrated to the dye. In the case of xanthene dyes, the actual xanthene heterocycle is present in the leuco compound. Details are given in the articles on the individual dyes.
literature
- Siegfried Hauptmann, Organic Chemistry , 1st edition, Harri Deutsch publishing house, Thun-Frankfurt a. M. 1985, pp. 758-759.
Individual evidence
- ↑ Entry on Pyronine. In: Römpp Online . Georg Thieme Verlag, accessed on July 1, 2020.