Pararosaniline Preparation

The first triaryknethane dyes were synthesized on a strictiy empirical basis in the late 1850s an example is fuchsine, which was prepared from the reaction of vinyl chloride with aniline. Thek stmctural relationship to triphenylmethane was estabHshed by Otto and Fmil Fischer (5) with the identification of pararosaniline [569-61-9] as 4,4, 4 -triaminotriphenyknethane and the stmctural elucidation of fuchsine. Several different stmctures have been assigned to the triaryknethane dyes (6—8), but none accounts precisely for the observed spectral characteristics. The triaryknethane dyes are therefore generally considered to be resonance hybrids. However, for convenience, usually only one hybrid is indicated, as shown for crystal violet [548-62-9] Cl Basic Violet 3 (1), for which = 589 nm. 

Rosaniline or magenta was originally obtained by oxidising with arsenic acid a mixture of aniline with 0- and />-toluidine. The product was then lixiviated and treated with common salt, which converted the ai senate into the hydrochloride of rosaniline. Pararosaniline was prepared in a similar way fiom a niixtuie of aniline and /-toluidine. The series... 

Measurements show some variation depending upon the staining solution used and the method of application. In dried and fixed smears, the cell wall and slime layer do not stain with weakly staining dyes such as methylene blue but do stain with the intensely staining pararosaniline, new fuchsin, crystal violet, and methyl violet. The great majority of bacteria have been measured in fixed and stained preparations. In some instances dried, negatively stained smears have been used. Therefore, the method employed should be specified when measurements of bacteria are reported otherwise the results will be of doubtful v alue. 

Several examples of typical triarylmethane dyes have already been mentioned, in particular, pararosaniline (6.161), malachite green (6.162) its o-chloro derivative (6.169), crystal violet (6.164), rosaniline (6.165) and diphenylamine blue (6.173). Cl Basic Green 1 (6.168 R = C2H5), the ethyl analogue of malachite green, is prepared by the aldehyde route and is isolated as the sulphate. The ethyl analogue of crystal violet is Cl Basic Violet 4 (6.167 R = C2H5) and is obtained by the ketone route. 

It is prepared by air oxidation of dimethylaniline in the presence of phenol and copper salts as well as sodium chloride. The reaction product consists of tetra- to hexamethylated pararosanilines (see 119, p. 541) ... 

The reagent is prepared by reaction of tris(4-aminophenyl)methanol (pararosaniline) with 4,5-dichlorophthalic anhydride followed by bromination with acetyl bromide. 

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 chemistry of the reactions taking place in the preparation of aldehyde green has been studied in detail with pararosaniline. 

The dyes of this group are not prepared from triphenylmethane, but the synthesis of pararosaniline from the hydrocarbon is of importance, as it established the structure of this dye which is the simplest member of the class. The steps involved in the transformation of triphenylmethane into pararosaniline are indicated by the following formulas —... 

The methods used to prepare the dyes of this class may be illustrated by a consideration of pararosaniline, rosaniline, methyl violet, crystal violet, and malachite green. 

Rosaniline is the color-base of magenta. The hydrochloride of the base is generally called magenta or fuchsine, although the acetate is also used under these names. Rosaniline is manufactured by ojddizing a mixture of aniline, o-toluidine, and p-toluidine, with arsenic acid, mercuric nitrate, or nitrobenzene. The reaction is analogous to that which takes place in the preparation of pararosaniline, of which rosaniline is a methyl derivative with the structure indicated by the following formula —... 

Crystal Violet.—The preparation of this dye, which is the chloride of hexamethyl-pararosaniline, illustrates a method of preparing dyes of this class. The compound is manufactured by treating dimethylaniline with carbonyl chloride or tetra-methyl-diamino-benzophenone chloride —... 

The electron-cytochemical method for localization of DPP was optimized by Lojda (1981) and its modification for cytochemical reaction for DPP in glutaraldehyde prefixed yeast cells was described recently (Voffsek in preparation). In principle, the synthetic dipeptide substrate has its carboxyl terminus bound to 4-methoxy-2-naphthylamine. The primary reaction product was formed by coupling hexazonium pararosaniline (HPR) with the MNA liberated by DPP and was osmiophilic. Thus postfixation by osmium tetrox-ide revealed also the electron-dense final reaction product on the background of the general osmiophilia of the matrix phase and membranes. 

Basic Red 9 (Pararosaniline) is the simplest triphenylmethane dye. It is prepared by the condensation of one mole of p-toluidine and two moles of aniline, usually by heating in nitrobenzene, which serves as solvent and oxidant. The first product is a colorless carbinol, which is converted to the dye with hydrochloric acid. 

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