Pararosaniline leuco base

In the preparation of commercial fuchsine aniline is heated with a mixture of ortho and para toluidine. p-Toluidine is oxidized to the aminoaldehyde which condenses with one molecule of both aniline and o-toluidine to form homorosaniline hydrochloride- At the same time there is also formed pararosaniline hydrochloride owing to the reaction of two molecules of aniline with the aldehyde. The differences in the structure of leuco base, color base, and dye are shown by comparison of their respective formulas (1), (2), and (3). 

The triphenylmethane dyes are salts formed by the action of acids on certain derivatives of triphenylcarbinol. For this reason these derivatives are called color-bases, although they are, themselves, colorless. By reduction the color-bases are converted into the so-called leuco-bases which are formed as the result of the replacement of the hydroxyl group of the car-bionl by hydrogen. The leuco-bases may be oxidized to the color-bases. In the case of pararosaniline the bases have the following formulas —... 

Pararosaniline can be converted into triphenylmethane the color-base is reduced by zinc and hydrochloric acid to the leuco-base, triaimno-triphenylmethane, which in turn is con-... 

Crystal violet (20) can be produced directly from formaldehyde and dimethyl-aniline. The methane base (18), WAfW,W-tetramethyl-4,4 -mcthylcncdianilinc, is formed initially. This is then oxidized to Michler s hydrol (12), which condenses with another molecule of dimethylaniline to give leuco crystal violet (19). The latter is converted to the dye in a second oxidation step. Pararosaniline, methyl violet, and Victoria blue can also be obtained by this reaction sequence. 

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