Basic violet

Rhoda.mines, Rhodamines are commercially the most important arninoxanthenes. If phthalic anhydride is used in place of formaldehyde in the above condensation reaction with y -dialkylarninophenol, a triphenyknethane analogue, 9-phenylxanthene, is produced. Historically, these have been called rhodamines. Rhodamine B (Basic Violet 10, Cl45170) (17) is usually manufactured by the condensation of two moles of y -diethylaminophenol with phthahc anhydride (24). An alternative route is the reaction of diethylamine with fluorescein dichloride [630-88-6] (3,6-dichlorofluoran) (18) under pressure. 

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. 

In the ketone method, the central carbon atom is derived from phosgene (qv). A diarylketone is prepared from phosgene and a tertiary arylamine and then condenses with another mole of a tertiary arylamine (same or different) in the presence of phosphoms oxychloride or zinc chloride. The dye is produced directly without an oxidation step. Thus, ethyl violet [2390-59-2] Cl Basic Violet 4 (15), is prepared from 4,4 -bis(diethylamino)benzophenone with diethylaruline in the presence of phosphoms oxychloride. This reaction is very useful for the preparation of unsymmetrical dyes. Condensation of 4,4 -bis(dimethylamino)benzophenone [90-94-8] (Michler s ketone) with AJ-phenjl-l-naphthylamine gives the Victoria Blue B [2580-56-5] Cl Basic Blue 26, which is used for coloring paper and producing ballpoint pen pastes and inks. 

In a variation of this method, isolation of the ben2hydrol derivative is not required. The methane base undergoes oxidative condensation in the presence of acid with the same or a different arylamine direcdy to the dye. New fuchsine [3248-91 -7] Cl Basic Violet 2 (16), is prepared by condensation of two moles of o-toluidine with formaldehyde in nitrobenzene in the presence of iron salts to give the corresponding substituted diphenylmethane base. This base is also not isolated, but undergoes an oxidative condensation with another mole of o-toluidine to produce the dye. 

Methyl violet [8004-87-3] Cl Basic Violet 1 (17), is made by the air oxidation of dimethyl aniline in the presence of salt, phenol, and a copper sulfate catalyst. Initially, some of the dimethyl aniline is oxidized to formaldehyde and /V-methyl aniline under those conditions. The formaldehyde then reacts with dimethyl aniline to produce N,N,]S7,1S7-tetramethyldiaminodiphenylmethane, which is oxidized to Michler s hydrol [119-58-4]. The hydrol condenses with... 

Barrellene oxide flash thermolysis oxirenes in, 7, 125 Basic Violet 10 (C.I. 45170), 3, 879 Batrachotoxin, 4, 374 Baumgarten method cinnoline synthesis, 3, 44... 

BASF Pharma/Knoll, See Abbott Laboratories (US), 219 BASF PharmaChemikalien GmbH Co. KG, 161 BASF Pigment GmbH, 161 Basic Violet, 10, 22 Bayer AG, 161... 

Although treated as separate classes in the Colour Index, these structural types are closely related and the few diphenylmethane dyes such as auramine (1.28 Cl Basic Yellow 2) are now of little practical interest. Commercial usage of the triarylmethane dyes and pigments has also declined considerably in favour of the major chemical classes. They were formerly noteworthy contributors to the acid, basic, mordant and solvent ranges, primarily in the violet, blue and green sectors. Numerous structural examples are recorded in the Colour Index. The terminal groupings can be amine/quinonimine, as in auramine and crystal violet (1.29 Cl Basic Violet 3), hydroxy/quinone, or both. The aryl nuclei are not always benzenoid (section 6.5). 

The resins used to make fluorescent pigments are usually toluenesulphonamide-melamine-formaldehyde matrices. The dyes used for this purpose include Cl Disperse Yellow 11, Rhodamine 6G (Cl Basic Red 1) and Rhodamine B (Cl Basic Violet 10). More details of the fluorescent dyes used have been given in a review by Christie [31]. 

Michler s ketone (6.155) and related carbonyl compounds can be used to obtain colour salts directly by reaction with a reactive intermediate such as an aromatic amine (the ketone synthesis), as in the case of crystal violet (6.164 Cl Basic Violet 3) shown in Scheme 6.31. 

A few triphenylmethane dyes are still obtained by empirical methods first used in the early processes of dye manufacture. For example, in the production of magenta (Cl Basic Violet 14), a mixture of aniline, toluidines and nitrotoluenes is heated with zinc and iron(II)... 

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. 

Hemicyanine (styryl) dyes are readily obtained by heating Fischer s base with an appropriate aldehyde. Typical products include Cl Basic Red 14 (6.224) and Cl Basic Violet 16 (6.225). The latter dye has been classified by ETAD as toxic [73]. 

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