Five-membered Monoheterocyclic Compounds (continued): The Indigo Group

Research output: Chapter or section in a book/report/conference proceedingChapter or section


The indigo group includes, in addition to indigotin and its derivatives, a variety or structurally related compounds, several of which, like the prototype are commercially important vat dyes. They are reducible by virtue of the carbonyl groups to dihydroxy compounds; these form water-soluble salts from solutions of which textile fibers can be impregnated with the reduced or “leuco” compound (generally colorless or much less highly colored than the parent), which is readily oxidized to reproduce the dye deposited in the textile material. The methods that are or have been applied technically to the manufacture of indigo depend for the main part on the production of indoxyl or indoxylic acid (indolin-3-one-2-carboxylic acid) with subsequent oxidation to indigotin by air or an oxidizing agent such as ferric chloride. The various derivatives of indigotin include N-derivatives, derivatives of the carbonyl function, homologs such as 5,5'-dimethylindigo, halogenoindigos, dehydroindigo, leuco-indigo (indigo-white) and polycyclic indigos. The position isomeride, indirubin, is present in small quantities in synthetic indigotin, and in larger and varying amounts in the natural dye; it is unlikely that it contributes significantly to the tinctorial properties of the coloring matter. Isoindigo or isoindigotin, produced by heating 3-diazo-oxindole, is the third possible bisindole indigo.
Original languageEnglish
Title of host publicationRodd's Chemistry of Carbon Compounds
Subtitle of host publicationA Modern Comprehensive Treatise
Number of pages27
ISBN (Print)9780444533456
Publication statusPublished - 1964


Dive into the research topics of 'Five-membered Monoheterocyclic Compounds (continued): The Indigo Group'. Together they form a unique fingerprint.

Cite this