Solvent Yellow 3

Nitro-l-diazo-2-naphthol-4-sulfonic acid prefers the 2-position in spite of the nitro group, and increasing alkalinity favors ortho coupling with diazophenols. 1-Naphthalenesulfamic acid [24344-19-2] (ArNHSO H) and N-nitro-1-naphthylamine [4323-69-7] (ArNHNO ) couple exclusively in the para position. The substitution of resorcinol [108-46-3] and y -phenylenediamine [108-45-2] is compHcated and has been discussed (29,30). The first azo dyes from aniline, eg. Aniline Yellow [60-09-3] (19) (Cl Solvent Yellow 1 Cl 11000) were manufactured in 1861 and Bismark Brown [10114-58-6] (20) (Cl Basic Brown 1 Cl 21000) appeared in 1863. The reaction is as follows ... 

Azo Dyes. The Colourindex classifications of dyes depend more on their historical eady use than on their stmctures, eg. Oil Orange is named Solvent Yellow 14, and a yellow for synthetic fibers is Disperse Yellow 23. 

In general, the azo colors are useful for coloring polystyrene, phenoHcs, and rigid poly(vinyl chloride). Many are compatible with poly(methyl methacrylate), but in this case the weatherabiUty of the resin far exceeds the life of the dyes. Among the more widely used azo dyes (qv) are Solvent Yellows 14 and 72 Orange 7 and Reds 1, 24, and 26. 

Quinophthalones provide important dyes for the coloration of plastics (eg, Cl Solvent Yellow 33 (71), R = H [5662-03-3]) and for the coloration of polyester. For example. Cl Disperse Yellow 54 (71) R = OH, is the lea ding yellow dye for the transfer printing of polyester. 

Sudan I (Solvent Yellow 14, l-phenylazo-2-naphthol) [824-07-9] M 248.3, m 135 , Cl 12055, Xmax 476nm, pKe,( -9.0. Crystd from EtOH. 

Henricsson, S. and Westerholm, R., Liquid chromatographic method for analysing the colour marker Solvent Yellow 124, N-ethyl-N-[2-(l-isobutoxy-ethoxy)ethyl](4-phenylazophenyl)amine, in diesel fuels, ]. Chromatogr. A, 723, 395, 1996. 

The most important 2 1 metal complex azo dyes are the 2 1 Cr3+ dyes. These may be symmetrical dyes, such as the water-soluble dye Cl Reactive Brown 10 (28), and the solvent-soluble dye Cl Solvent Yellow 21 (29), used in varnishes as a wood stain. They may also be unsymmetrical complexes, such as Cl Acid Violet 121 (30), used for dyeing wool and nylon. 

These unexacting requirements make the simplest unsulphonated azo structures, often monoazo types, quite acceptable [80]. Typical of the least polar members of this class are Cl Solvent Yellow 2 (4-68), Cl Solvent Orange 1 (4.69) and Cl Solvent Red 17 (4.70). Simple azo structures carrying sulphonamide, sulphone or carboxylate ester groups are used where a somewhat more polar, less soluble dye is needed. Simple disazo compounds (4-amino-azobenzene— 2-naphthol, for example) are used as red solvent dyes. Probably the only structural feature worthy of note in this class is the occasional adoption of structures carrying long alkyl chains to enhance solubility, as in the case of the disazo dye Cl Solvent Yellow 107 (4.71). 

Quinophthalone (6.229) and its derivatives [86] also fall into the methine category, although they appear in the Colour Index under quinoline colouring matters. The parent compound was discovered in 1882 by Jacobsen, who condensed 2-methylquinoline (quinaldine) with phthalic anhydride. The product, quinoline yellow, is used as a solvent dye (Cl Solvent Yellow 33). The light fastness is improved by the presence of a hydroxy group in the quinoline ring system. Derivatives of this type provide greenish yellow disperse dyes for polyester. The moderate sublimation fastness of Cl Disperse Yellow 54 (6.230 R = H) is improved by the introduction of an adjacent bromine atom in Cl Disperse Yellow 64 (6.230 R = Br). 

The chromium complexes of some azomethine derivatives are used as solvent dyes. Cl Solvent Yellow 32 (6.231) is an example, obtained by condensing one mole of salicyl-aldehyde with the appropriate amine, followed by treatment with one equivalent of chromium. 

Fig. 3.59. HPLC-UV chromatogram at 230 nm for the analysis of azo dyes, (a) Disperse red 1 (b) Solvent yellow 14 (c) Solvent red 24. Reprinted with permission from M. C. Garrigos el al. [129].

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