Induline is a dye of blue, bluish-red or black shades. Induline consists of a mixture of several intensely colored species, so the name is often indulines. It was one of the first synthetic dyes, discovered in 1863 by J. Dale and

Heinrich Caro Heinrich Caro (February 13, 1834 in Posen, Prussia Germany now Poznań, Poland – September 11, 1910 in Dresden), was a German chemist. He was a Sephardic Jew. He started his study of chemistry at the Friedrich Wilhelms University and later ...

. The main components of induline are various substituted

phenazine Phenazine is an organic compound with the formula (C6H4)2N2. It is a dibenzo annulated pyrazine, and the parent substance of many dyestuffs, such as the toluylene red, indulines, and safranines (and the closely related eurhodines). Phenazine ...

s. Although induline no longer in use, the related dye nigrosin is still produced commercially. IndulineChemDraw

Relationship to other compounds

Induline is a derivative of the eurhodines (aminophenazines, aminonaphthophenazines). By means of their diazo derivatives can be de-amidated, yielding in this way azonium

salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quant ...

s; consequently they may be considered as amidated azonium salts. The first reaction giving a clue to their constitution was the isolation of the intermediate azophenin by O. Witt, which was proved by Fischer and Hepp to be dianilidoquinone dianil, a similar intermediate compound being found shortly afterwards in the naphthalene series. Azophenin, C₃₀H₂₄N₄, is prepared by warming quinone dianil with

aniline Aniline is an organic compound with the formula C6 H5 NH2. Consisting of a phenyl group attached to an amino group, aniline is the simplest aromatic amine. It is an industrially significant commodity chemical, as well as a versatile starti ...

, by melting together quinone, aniline and aniline

hydrochloride In chemistry, a hydrochloride is an acid salt resulting, or regarded as resulting, from the reaction of hydrochloric acid with an organic base (e.g. an amine). An alternative name is chlorhydrate, which comes from French. An archaic alternative n ...

, or by the action of aniline on para-nitrosophenol or para-nitrosodiphenylamine. The indulines are prepared as mentioned above from aminoazo compounds, or by condensing oxy- and amido-quinones with phenylated ortho-diamines. The indulines may be subdivided into the following groups: (1) benzindulines, derivatives of phenazine; (2) isorosindulines; and (3) rosindulines, both derived from naphthophenazine; and (4) naphthindulines, derived from naphthazine. The rosindulines and naphthindulines have a strongly basic character, and their

s possess a marked red color and

fluorescence Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence. In most cases, the emitted light has a longer wavelength, and therefore a lower photon energy, tha ...

. Benzinduline (aposafranine), C₁₈H₁₃N₃, is a strong base, but cannot be diazotized, unless it be dissolved in concentrated

mineral acid A mineral acid (or inorganic acid) is an acid derived from one or more inorganic compounds, as opposed to organic acids which are acidic, organic compounds. All mineral acids form hydrogen ions and the conjugate base when dissolved in water. Cha ...

s. When warmed with aniline it yields anilido-aposafranine, which may also be obtained by the direct

oxidation Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a ...

of ortho-aminodiphenylamine. Isorosinduline is obtained from quinone dichlorimide and phenyl-β-naphthylamine; rosinduline from benzene-azo-α-naphthylamine and aniline and naphthinduline from benzene-azo-α-naphthylamine and naphthylamine.

References

{{reflist Dyes