Disperse Azo Dyes

Disperse azo dyes for dyeing polyester textile material... 

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). 

Nitrosylsulfuric acid is used in making caprolactam from benzoic acid and in preparing many disperse azo dyes. Other apphcations are bleaching, maturing, dough-conditioning cereal products, and in preparing crystalline diazonium sulfates. 

In making disperse azo dyes, nitrosylsulfuric acid is produced by the addition of sodium nitrite, NaN02, to concentrated sulfuric acid (Ig NaN02 per 13 g H2SO4)... 

In the following survey, the most important disperse azo dyes are divided into mono- and disazo types then each of these classes is subdivided according to the diazo and the coupling components. The diazo component is further subdivided where appropriate into aromatic and heteroaromatic amines. 

Of all the disperse azo dyes, this class has the greatest economic importance. Commercial products are most often represented by structure 2, in which 4-nitroaniline [100-01-6] and its substituted derivatives constitute the diazo component. 

Oprea, T.I., Kurunczi, L. and Timofei, S. (1997) QSAR studies of disperse azo dyes. Towards the negation of the pharmacophore theory of dye-fiber interaction Dyes S, Pigments, 33, 41-64. 

Some researcher reported that photofading behaviour of a series of disperse azo dyes in polyester and nylon films may involve the initial oxidation of dye to the azoxy form, followed by a Wallach photorearrangement (Leaver I.H., 1980) to give an o-hydroxyazo dye (see scheme II) ... 

Scheme II Photooxidation of disperse azo dyes involved the formation of the azoxy form and Wallach photorearrangement...

The reduction of several water-insoluble disperse azo dyes in anaerobic sediment-water systems also has been reported. For example, reduction of Disperse Blue 79, the largest volume textile dye on the market today, was reduced in anoxic sediment slurries with half-lives on the order of 1 to 5 hours (Weber, 1988). Reduction appears to occur initially across the azo linkage and results in formation of 2-bromo-4,6-dinitroaniline (BDNA) and the substituted 1,4-phenylenediamine, (A) (Figure 3.5). 

Compared with other classes of chemicals, azo d es make a relatively small contribution to the total mass of pollutants released into the environment. However, because they are hi ily coloured, contamination by these chemicals, when it occurs, is readily apparent. Moreover, in locales, where dyes are synthesized and used, thw presence in ground water and surface water may represent important pollution problems. For example, the Coosa River Basin and its tributaries in Northwest Georgia contain approximately 50% of all carpet dyeing wastewater in the United States concentrations of acid azo dyes in Coosa River Basin water samples often being present in the parts per billion to the low psirts per million level [3]. Sediment samples fix>m the same source revealed the presence of several acid azo dyes as well as several disperse azo dyes in the parts per billion to parts per million range [3]. 

Seidenari S, Manzini M, Schiavi ME, Motolese A (1995) Prevalence of contact allergy to non-disperse azo dyes for natural fibers a study in 1814 consecutive patients. Contact Dermatitis 33 118-122... 

The first hyperpolarizability of disperse azo dyes derived from 2-amino-5-nitrothiazole has been evaluated at the PM3 level of approximation and... 

We have analyzed the nature of the dye-fiber interaction for 27 disperse azo dyes by means of several QSAR methodsbased on the pharmacophore theory of dye-fiber interaction. Hydrophobic effects were excluded because CLOGP gave a limited correlation, = 0.32. MTD (r = 0.924) and CoMFA (j-2 = 0.925 and = 0.776, LOO) results emphasized the importance of steric contributions for enhancing the affinity to cellulose fiber. CoMFA results apparently confirm the validity erf the pharmacophore theory of dye-fiber interaction. This was not surprising because similar results between CoMFA and MTD were reported in 1993. ... 

Table 4 Summary of CV2 Results for Disperse Azo Dyes QSAR...

Figure 6 Molecular loigth is the major feature controlling cellulose affinity for this series of disperse azo dyes (Ref. 124). Beneficial CoMFA stmc fields ate shown, in orthogonal views, for the most active compound.

Disperse Azo Dyes. Towards the Negation of the Pharmacophore Theory of Dye-Fiber Interaction ... 

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