Thioindigo scarlet

Isatin is the inner anhydride (lactam) of a y-amino-a-ketocarboxylic acid, isatinic acid (A), and is converted into a salt of this acid by the action of alkali. The keto-group in position 3 can condense with many other substances, and for this reason isatin is manufactured on a technical scale and converted into valuable indigoid vat dyes. The magnificent thioindigo scarlet, which is obtained from isatin and a sulphur analogue of indoxyl (the so-called hydroxythionaphthene), may be taken as example qq... 

Mercury Diphenyl Dimethylpyrone 1 5-Dibromopentane Diphenylnitrio Oxide Thioindigotin Thioindigo Scarlet Isatin (Sandmeyer s method)... 

This product separates immediately- when 3-hydroxy selenonaphthene and isatin in alcohol solution are warmed together in the presence of a little piperidine. It forms red silky needles, which sublime undecomposed at about 250° C. and melt at about 350° C. In nitrobenzene it is readily- soluble, but sparingly soluble in xyriene the concentrated sulphuric acid solution is olive green. With alkali and hydrosulphite it gives a yellow vat, which dyes a bluer shade than Thioindigo Scarlet. 

Algole red 5 G and scarlet G, algole pink R. ciba red G and scarlet G, ciba Bordeaux B, helindone red B and 3 B, helindone scarlet S. helindone fast scarlet R, thioindlgo red B, thioindigo scarlet, 0 vat red. 

Thioindigo scarlet R (Kalle) dibroiiio derivative = Ciba RedG... 

Helindone red, scarlet, fast scarlet and pink, ciba red and scarlet, thioindigo red, thiotndigo scarlet, vat red, etc. 

The most widely used red pigments in automotive applications are the quinacridones, due to their good colour and solvent fastness. These vary in shade from scarlet through to violet and maroon. Toluidine and thioindigo reds are also used. 

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