Acid Red dyes

Another comprehensive evaluation of cotton dyeing parameters has been carried out for eighteen isomeric monoazo H acid red dyes containing aminochlorotriazine and... 

Organic phase chloroform Aqueous phase 0.1 mM of pairing ion in water. Solutes sodium cromoglycate (circles) and acid red dye I (triangles). Figure taken from ref. [385]. Reprinted with permission. 

PVP is a nonionic water-soluble polymer that interacts with water-soluble dyes to form water-soluble complexes with less fabric substantivity than the free dye. Additionally, PVP inhibits soil redeposition and is particularly effective with synthetic fibers and synthetic cotton blends. The polymer comprises hydrophilic, dipolar imido groups in conjunction with hydrophobic, apolar methylene and methine groups. The combination of dipolar and amphiphilic character make PVP soluble in water and organic solvents such as alcohols and partially halogenated alkanes, and will complex a variety of polarizable and acidic compounds. PVP is particularly effective with blue dyes and not as effective with acid red dyes. 

Another group of halogenated fluorescein dyes is prepared by condensing chloro derivatives of phthalic anhydride with resorcinol, followed by bromination or iodination. Thus Phloxine B /78472-87-2] (Acid Red 92, Cl45410) (42) is prepared by condensing tetrachlorophthaUc anhydride with resorcinol followed by tetrabromination. Phloxine B undergoes ethylation to yield the yellowish ted acid dye Cyanosine B [6441-80-1] (43). 

Make acid yields coumaUc acid when treated with fuming sulfuric acid (19). Similar treatment of malic acid in the presence of phenol and substituted phenols is a facile method of synthesi2ing coumarins that are substituted in the aromatic nucleus (20,21) (see Coumarin). Similar reactions take place with thiophenol and substituted thiophenols, yielding, among other compounds, a red dye (22) (see Dyes and dye intermediates). Oxidation of an aqueous solution of malic acid with hydrogen peroxide (qv) cataly2ed by ferrous ions yields oxalacetic acid (23). If this oxidation is performed in the presence of chromium, ferric, or titanium ions, or mixtures of these, the product is tartaric acid (24). Chlorals react with malic acid in the presence of sulfuric acid or other acidic catalysts to produce 4-ketodioxolones (25,26). 

Amino-4,6-dinitropheno1 is an important intermediate in the manufacture of colorants, especially mordant dyes. It has also been used as an indicator dye in titrations (yellow with acid, red with alkali) and as a reagent for albumin deterrnination. 

Changes in the backbone of the sulfonic acid azo dyes often produce drastic changes in properties of the materials. The disulfonic acid (5) is somewhat similar to (3), but is used to color leather red (77). More esoteric dyes have also been developed based on sulfonic acid metal complexes and chitosan-derived materials (78,79). 

Phenylrosinduline (11) has been sulfonated to Cl Acid Red 101, Cl 50085, (12) such dyes are no longer commercial items. 

With Orange I [574-69-6] (34) (Cl Acid Orange 20 Cl 14600) the naphthalene moiety was iatroduced to azo chemistry. Basacid Red 340 [1658-56-6] (35) (Cl Acid Red 88 Cl 15620) the first red azo dye of technical value was discovered by BASF ia 1876. Its previous name was Fast Red AV and it is stiU produced ia large amounts ia the United States because of its low cost and good dyeiag and fastness properties. This dye became the prototype of a large number of red azo dyes that were developed simultaneously with the iatroduction of new derivatives of naphthalene. 

Economically, the most important acid red is Acid Red 151. This disazo dye (39) is obtained by coupling -aminophenylazo)benzenesulfonic acid to 2-naphthol. 

Other disazo dyes with good substantivity and high wet-fastness properties on polyamides are Acid Red 114 (40), made by coupling o-toHdine to phenol which is then coupled to G-acid, followed by reaction of the phenoHc hydroxyl group with -toluenesulfonyl chloride, and Acid Blue 113 (41) (metanilic acid — 1-naphthylamine — 8-anilino-1-naphthalenesulfonic acid). 

Certain dyes when appHed by the afterchrome method are oxidized prior to metal complex formation. Examples iaclude. Chromotrope EB [3567-69-9] (52) (Cl Acid Red 14 Cl 14720) (naphthionic acid — l-naphthol-4-sulfonic acid) ia which a hydroxyl group is iatroduced by oxidation at the... 

Direct Reds. The principal commercially produced direct reds, with revealed chemistry, are of disazo or polyazo composition (Table 6). Direct Red 81 (68) is manufactured by couplingp- -aminopheny1azo)henzenesu1fonic acid to A/-benzoyl J-acid Other important direct red dyes iaclude those shown ia Figure 5. 

Fig. 5. Direct red dyes, (a) Direct Red 81 described ia text (68) (b) Direct Red 2 (o-toLidiae coupled to two moles of naphthionic acid) (69) (c) Direct Red 23 (aniline coupled to 6,6 -ureylenebis-l-naplitliol-3-sulfonic acid with a second coupling with j aminoacetanilide) (70) and Direct Red 80 (2 mol 6-amino-3,4 -azobenzenedisulfonic acid coupled twice to 6,6 -ureylenebis-l-naphthol-3-sulfonic acid) (73). Direct Red 24 (4-aniino-y -toluenesulfonic acid coupled under acidic conditions to 6,6 -ureylenebis-l-naphthol-3-sulfonic acid followed by an alkaline coupling of o-anisidine) (71) (d) Direct Red 72 (Broenner s acid, ie, 6-artiino-2-naphthalenesulfonic acid coupled under acidic conditions to 6,6 -ureylenebis-l-naphthol-3-sulfonic acid followed by an...

Commercial Disperse Azo Dyes. The first proposal to use insoluble dyes in suspension in an aqueous foam bath, ie, disperse dyes, to dye cellulose acetate was in 1921 (60). Commercialization of disperse dyes began in 1924 with the introduction of the Duranol dyes by British Dyestuffs Corporation (61) and the SRA dyes by British Celanese Company (62). In contrast to the acid monoazo dyes, derivatives of benzene rather than of naphthalene are of the greatest importance as coupling components. Among these components mono- and dialkylariifines (especially A/-P-hydroxyethyl-and A/-(3-acetoxyethylanifine derivatives) are widely used couplers. Nitrodiazobenzenes are widely used as diazo components. A typical example is CeUiton Scarlet B [2872-52-8] (91) (Cl Disperse Red 1 Cl 11110). 

Xanthene Dyes. This class is best represented by Rhodamine B. It has high fluorescent brilliance but poor light and heat stabihty it may be used in phenohcs. Sulfo Rhodamine is stable and is useflil in nylon-6,6. Other xanthenes used in acryhcs, polystyrene, and rigid poly(vinyl chloride) are Solvent Green 4, Acid Red 52, Basic Red 1, and Solvent Orange 63 (see Xanthene dyes). 

The Cl name for a dye is derived from the appHcation class to which the dye belongs, the color or hue of the dye, and a sequential number, eg. Cl Acid Yellow 3, Cl Acid Red 266, Cl Basic Blue 41, and Cl Vat Black 7. A five digit Cl number is assigned to a dye when its chemical stmcture has been made known by the manufacturer. The following example illustrates these points, where CA indicates Chemicalj bstracts and Cl Colourindex. 

Carmine [1390-65-4] is the trade name for the aluminum lake of the red anthraquinone dye carminic acid obtained from the cochineal bug. The dye is obtained from the powdery form of cochineal by extraction with hot water, the extracts treated with aluminum salts, and the dye precipitated from the solution by the addition of ethanol. This water-soluble bright red dye is used for coloring shrimp, pork sausages, pharmaceuticals, and cosmetics. It is the only animal-derived dye approved as a colorant for foods and other products. 

Many red dyes are based on H-acid [90-20-0] (11), eg, Reactive Reds 2, 24, and 218. Others are substituted phenyl and naphthyl or metallised systems (7) (Table 2). Violet dyes are also metallised monoaso dyes (7). 

Lac is derived from lac resin, the hardened secretion of the lac insect, the only known resin of animal origin. The lac insect, Kerria lacca, formerly known as Laccifer lacca, is a natural parasite of a variety of trees in large areas of southern Asia. Three different products are derived from lac resin lac dye, lac wax, and shellac. To obtain the lac resin, twigs encrusted with the secretion of the insects are cut down from the trees, then the incrustation is separated from the twigs, washed with water, and filtered. The wax and shellac, which are insoluble in water, remain as a solid residue of the filtration, while the soluble red dye (lac) is obtained as a powder when the water from the filtered solution is evaporated. The coloring matter in lac dye is an organic compound known as laccaic acid. 

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