Green, Acid Malachite

Carboxylic acid Malachite green, Cystamine-Ellman s reagent - ... 

Triphenylmethane dyes are usually prepared in two steps 1) condensation of an N,N-dialkylaniline with a benzaldehyde compound and 2) oxidation of the resultant leuco base (27). The synthesis of C.I. Basic Green 4 (Malachite Green) is given as an example in Fig. 13.106. Alternatively, C.I. Acid Green 50 is prepared in three steps 1) condensation of... 

Titration is carried out to a colorless endpoint, which is usually very sharp. Knecht has titrated fuchsin, eosin, malachite green, acid... 

Methods based on extractable associates of the reduced form of molybdoarsenic acid with Crystal Violet (e=3.1 10 ). Methyl Violet, Brilliant Green, or Malachite Green have also been applied [54]. 

Victoria Green 3 B is a chlorinated malachite green prepared from dichlorobenzoic aldehyde and dimethylaniline. The introduction of halogen leads to the formation of a dye which yields bluer shades of green than malachite green. The sulphonic acid derivatives of these dyes, as well as those derived from dimethylaniline, are also manufactured. 

Fig. 7 Charge-transfer interactions, (a) Crystal structure of stoichiometric hydrogen phthalatelmalachite green complex. Photograph (b) and ideal representation (c) of phthalic acid/malachite green mixed crystal. (View this an in color.at www.dekker.com.)...

Production of N,N-dimethylaniline in Western Europe in 1985 was around 9,0001. Among the most important compounds based on N,N-dimethylaniline is Michler s ketone, which is used to manufacture triphenylmethane dyes such as Basic Violet 3 (Crystal Violet) or Basic Green 4 (Malachite Green), which is obtainable by reaction with benzaldehyde in a sulfuric acid medium, followed by oxidation. 

A second method for the synthesis of triphenylmethane dyes is illustrated with Basic Green 4 (Malachite Green). Benzalde-hyde (one mole) is condensed with two moles of Af,Af-dimethylaniline to form a leuco base, which is oxidized with lead peroxide and treated with hydrochloric acid to give the dye. 

Titrations with dibutylamine [111-92-2] can also be used to determine the NCO content of isocyanates and prepolymers. Generally, an excess of amine in a suitable solvent such as chlorobenzene [108-90-7] is added to the sample. The resulting solution is allowed to react and the unreacted amine is back- titrated with dilute hydrochloric acid. For low NCO content levels, a colorimetric method is often used. The isocyanate-containing species is titrated with amine and the unreacted amine is deterrnined using malachite green [569-64-2]. 

The triaryknethane dyes are broadly classified into the triphenyknethanes (Cl 42000—43875), diphenylnaphthyknethanes (Cl 44000—44100), and miscellaneous triphenylmethane derivatives (Cl 44500—44535). The triphenyknethanes are classified further on the basis of substitution in the aromatic nuclei, as follows (/) diamino derivatives of triphenylmethane, ie, dyes of the malachite green series (Cl 42000—42175) (2) triamino derivatives of triphenylmethane, ie, dyes of the fuchsine, rosaniline, or magenta series (Cl 42500—42800) (J) aminohydroxy derivatives of triphenylmethane (Cl 43500—43570) and (4) hydroxy derivatives of triphenylmethane, ie, dyes of the rosoHc acid series (Cl 43800—43875). Monoaminotriphenyknethanes are known but they are not included in the classification because they have Httie value as dyes. 

The central carbon atom is derived from an aromatic aldehyde or a substance capable of generating an aldehyde during the course of the condensation. Malachite green is prepared by heating benzaldehyde under reflux with a slight excess of dimethyl aniline in aqueous acid (Fig. 2). The reaction mass is made alkaline and the excess dimethylaniline is removed by steam distillation. The resulting leuco base is oxidized with freshly prepared lead dioxide to the carbinol base, and the lead is removed by precipitation as the sulfate. Subsequent treatment of the carbinol base with acid produces the dye, which can be isolated as the chloride, the oxalate [2437-29-8] or the zinc chloride double salt [79118-82-4]. 

Statistics for the production of basic dyes include those products hsted as cationic dyes, eg, cyanines, for dyeing polyacrylonitrile fibers and the classical triaryhnethane dyes, eg, malachite green, for coloring paper and other office apphcations (2,53). Moreover, statistics for triaryhnethane dyes are also hidden in the production figures for acid, solvent, mordant, and food dyes, and also organic pigments. Between 1975 and 1984, the aimual production of basic dyes in the United States varied from 5000—7700 t. However, from 1985—1990, aimual production of basic dyes varied from 5000—5700 t, and the annual sales value increased from 56 to 73 million per year. 

Malachite green (0.0...2.0) uracil derivatives, triazine herbicides [163] polar lipids [246, 247] phospholipids [248, 249] fatty acids, fatty aldehydes, phospholipids and glycolipids [250] microbiocidal isothiazolones [251]... 

MACB=5-chloro-2-(methylamino)benzo-phenone la 227 Macrolide antibiotics la 195 Magnesium cations lal44,145,311,312 Malachite green la 45 Malathion lb 83, 304, 305,338,340,341 Maleic acid la 44,61,171,230,249,250 Malic acid la 45,175,230,233,250,258, 259,308... 

Another approach to improve the color formation properties of Malachite Green lactone has been the introduction of nitrogen atoms into the phthalide ring. Thus, condensation of pyridine-2,3-dicarboxylic acid anhydride with dimethylaniline in the presence of zinc chloride has been shown54 to yield a mixture of the 4- and 7-azaphthalides 11 and 12. 

DC11 Malachite Green, Basic Blue efficiency (95-98%) achieved within 6 h for 100 mM Acid Blue 25 (anthraquinone dye), 4 h for 55 mM Malachite Green (triphenylmethane dye), and 2 h for 750 mM Basic Blue X-GRRL under anaerobic conditions ... 

However, malachite green [188] gave a stable dark yellow species in 1.5 M sulfuric acid (probably a protonated one), whereas ethyl violet became colourless within 30 min even in only 0.5 M sulfuric acid. 

In the malachite green procedure, 10 ml of the sample solution containing up to 0.7 xg phosphorus as orthophosphate was transferred into a 25 ml test tube. To this solution was added 1 ml each of 4.5 M sulfuric acid and the reagent solution. The solution was shaken with 5 ml of a 1 3 v/v mixture of toluene and 4-methylpentan-2-one for 5 min. After phase separation, the absorbance of the organic phase was measured at 630 nm against a reagent blank in 1 cm cells. 

The basic dyes are usually marketed as chlorides, oxalates or zinc chloride double salts in the case of malachite green (6.162), the last-named derivative has the formula 3 [Dye]C1.2ZnCl2.2H20. Acid dyes of this type are often isolated as the sodium salt. 

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