Indoxyl

• 3- indolin ( keto form )
• 3 -hydroxyindole ( enol form)

Pale yellow crystals

Fixed

85 ° C.

Soluble in water, alkalis, ethanol and diethyl ether

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Indoxyl is a derivative of indole and is used as a dye precursor in the natural and synthetic preparation of indigo.

Indoxyl formed in the hydrolysis of the glycoside indican occur in plants ( indoxyl - β -D-glucoside ) by fermentation (see indigo production).

Production

In the course of the synthesis of indigo, the chemical company BASF and Hoechst AG have developed the so-called Heumann - Pfleger- synthesis. It is derived from anthranilic indoxyl:

Properties

In an alkaline medium, the water-soluble, yellow indoxyl is oxidized by the oxygen of the air to the water-insoluble dark blue dye ( pigment) Indigo. In this case, four electrons (e - ) and four protons (H ) are transferred to an oxygen molecule.

Indoxyl in aqueous solution shows a yellow-green fluorescence. Indoxyl is in equilibrium with an enol form and keto form ( keto -enol tautomerism ). Spectroscopic findings show, however, that in indoxyl this equilibrium is almost completely shifted to the keto form.

Use

Some synthetic indoxyl derivatives find use in biochemistry:

• BCIP and X -Phos (5- bromo-4- chloro-3- indoxyl phosphate )
• X-Gal (5- bromo-4- chloro-3- indoxyl - β -D-galactopyranoside )
• X -Gluc (5- bromo-4- chloro-3- indolyl- β -D -glucuronic acid )