Aniline blue, production

This is the first product of the action of sulphuric acid on aniline blue. The free acid is obtained as a blue amorphous... 

By continued action of aniline on aniline black, products resembling the indulines are formed. One of these has heen isolated, and is a blue dyestuff of the formula, C3eH2 N5 or [18]... 

The new aniline dye companies in Europe displayed their wares at the 1862 London International Exhibition, where Hofmann, as juror, acquired a number of samples. They included a blue (7) discovered, almost by chance, by two French chemists working near London in 1861. It had first appeared when excess aniline was erroneously added to the aniline red reaction mixture. E. C. Nicholson in 1862 treated the aniline blue with sulfuric acid to yield a more valuable product, the soluble alkali blue, later better known as Cl [Colour Index] Pigment Blue 61. In May 1863, Hofmann found that the aniline blue was a substitution product of aniline red in which three phenyl groups had replaced three hydrogens (Scheme 2). This immediately suggested that other substituted derivatives might be made and perhaps even provide new aniline dyes. Alkylation with ethyl iodide showed that this was indeed correct. Hofmann achieved stepwise replacement of three hydrogens to afford colorants that were, successively, reddish violet, violet blue and then violet, what were soon known as the Hofmann s violets (8). Hofmann next turned to the aniline red process, and found that the colorant was formed not from aniline alone... 

The biggest advantage of this flexible jet technique is the high entrapment efficiency of more than 80 %. We calculated these special features from UV-Vis measurements measuring the Aniline Blue concentration one hour after the vesicle production. The absorption of this blue dye after the destruction of the vesicles by adding Triton X 100 was taken as the reference and compared to the absorption before the destruction of the vesicular stractures. 

Aniline was first isolated in 1826 as a degradation product of indigo, a dark blue dye obtained from the West Indian plant Indigofera anil, from which the name aniline is derived. 

Trypan Red Paper. Prepd as above from product supplied by the Allied Chemical Dye Corp Rose-red - Light violet -> Bleached 0.1% Ethyl Violet Paper. Prepd as above from product supplied by National Aniline Dye Co Medium violet Blue - Bleached... 

A mixture consisting of aniline ( 0.2 g) and (lS)-(+) camphorsulfonic acid (3.48 g) was dissolved in 10 ml of water and then treated with five separate portions of 0.1 g of ammonium peroxydisulfate dissolved in 1 ml water. Each successive portion was added when the solution turned from blue to green while the reaction mixture was maintained at 20°C. After the additions were completed the mixture was centrifuged and the product washed with water. The circular dichroism spectrum of the product suspensed in water indicated a molar ellipticity of about 90 x 103 deg-cm2/dmol. Transmission electron micrographs showed that the product had a nanofibrous structure with fiber diameters from 30 to 70 nm and had a length of several hundred nanometers. 

The crude product is purified by recrystallization from 160-180 ml. of acetic acid. The solution (Note 1) is allowed to cool slowly to room temperature, and -tricyanovinyl-N,N-dimethyl-aniline is collected on a Buchner funnel and washed successively with 20 ml. of methanol and 40 ml. of ether. The product, 23-26 g. (52-58%), is obtained as dark-blue needles, m.p. 173-175° (Note 2). 

Dyes with 2-amino-6-methoxybenzothiazole as diazo component are of industrial importance because their alkylated products dye polyacrylonitrile in clear, very lightfast, blue shades. With AfJV-dim ethyl aniline as coupling component, C.I. Basic Blue 54, 11052 [1500-59-6] is obtained. 

Sulfonation. The direct sulfonation of alkylaminotriphenylmethane dyes gives mixtures of substituted products. Although dyes containing anilino or benzylamino groups give more selective substitution, a sulfonated intermediate such as 3[(N-ethyl-N-phenylamino)methyl]benzenesulfonic acid (ethylbenzylanilinesulfonic acid) is the preferred starting material. However, Patent Blue V [354649-0], Cl Acid Blue 3, was made from 3-hydroxybenzaldehyde and two moles of diethyl aniline, followed by sulfonation of the leuco base and oxidation to the dye. FD C Green 2 [5141 -20-8/,... 

The monoazo dye is not isolated. An excess of diazotized aniline has a deleterious effect. The naphthol blue-black B is salted out at 90°C. with 15 per cent salt to yield a lustrous, bronzy product. This dye, on reduction with Na2S at 25°, yields a valuable dark green azo dye, azo dark green, having the structure ... 

Mixed solutions of potassium ferrocyanide and p-nitroso dimethyl aniline are at first yellow m colour, but become green very rapidly on exposure to light, due, perhaps, to the production of colloidal Prussian blue under the influence of a catalyst generated by the rntroso compound.3... 

With aniline it forms addition products which separate in beautiful steel blue needles. 

The amount of aniline used in the manufacture of blue is of great importance. In presence of a large excess of aniline the phenylation is more complete and rapid than when a small quantity is used. For production of pure triphenylrosaniline (green shade of blue) a large excess of aniline is used (ten times the theoretical amount) along with a correspondingly large amount of... 

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