Reactive dyes chromogenic groups

Versatility - it must be possible to attach the reactive system to a variety of dye chromogenic groupings in manufacture. 

Reactive dyes are synthesized by (/) condensation of an amine function in the chromogen molecule with a reactive group, eg. 

In contrast to direct dyes, metal-complex azo reactive dyes are almost always monoazo chromogens coordinated to one copper(II) ion per molecule. The important structural types include phenylazo J acid reds (5.47), phenylazo H acid violets (5.48) and naphthylazo H acid blues (5.49), where Z represents the reactive system attached through the imino group in the coupling component. Less often the reactive system is located on the diazo component, as in Cl Reactive Violet 5 (5.50) and analogous red to blue members of various ranges. 

Selecting a sulphonated dye molecule containing an amino group as the nucleophile leads directly to a dichlorotriazine dye. In certain cases a suitable intermediate may be condensed with cyanuric chloride and then the chromogenic grouping is synthesised from this reaction product. Both of these routes are illustrated in a simple way for Cl Reactive Red 1 (7.1) in Scheme 7.7. In these dyes the electronic effects responsible for the lability of the chloro substituents are muted by feedback of electrons from the electron-donating imino bridging... 

Several different approaches have been employed in order to build the bifunctionality concept into known dye chromogens. In the case of bis(dichlorotriazine) dyes, which were not exploited commercially, only the arrangement 7.55 is feasible. The difficulty of introducing sufficient extra sulphonic acid groups into the chromogen to compensate for the presence of these two reactive systems and provide adequate solubility and mobility at the low dyeing temperature necessary for such highly reactive molecules proved insuperable. 

Reactive dyes are colored compounds that contain groups capable of forming covalent bonds between dye and substrate. Approximately 80-90% of reactive dyes are azo dyes. The other chromogenic classes are anthraquinones, dioxazines, phthalocyanines, and some 1 1 copper azo complexes. Reactive 1 2 complex leather dyes were also commercially manufactured for a short time. Constitution and producer have not been disclosed. 

Triazines. The most commercially important ttia2ine is 2,4,6-ttichloro-j -ttia2ine [108-77-0] (cyanutic chloride, (99)). Cyanutic chloride has not achieved prominence because of its value as part of a chromogen but because of its use for attaching dyestuffs to cellulose, ie, as a reactive group (see Dyes, reactive). This innovation was first introduced by ICl in 1956, and since then other active halogen compounds have been introduced. 

This small class of blue copper-complex dyes has made a significant contribution to the acid and reactive ranges in recent years (sections 5.4.2, 5.4-3 and 7.5.8). The essential chromogen is the bicyclic 1 1 chelated grouping illustrated (1.20). Trivalent metals such as chromium, nickel or cobalt will give tetracyclic 1 2 complexes with a central metal atom, analogous to conventional 1 2 metal-complex azo dyes. 

The marked differences in substantivity between the various forms of monofunctional vinylsulphone dyes (section 7.3.8) recur to a moderated extent in the Sumifix Supra dyes because of the influence of the substantive triazine ring. The scarlet chromogen (7.77) linked via a chlorotriazine unit to the three variants of the vinylsulphone grouping showed similar trends (Table 7.4) to those already seen for those of Cl Reactive Red 22 tested under the same conditions (Table 7.3). The rate of secondary exhaustion will be easier to control in this instance because of the lower difference in substantivity between the precursor and the vinylsulphone form [37]. 

An example of a reactive dyestuff is Procion Brilliant Orange GS (Reactive Orange 1), which is a derivative of J-acid. The triazine group does not act as chromogen in this case, but as an anchor to fix the dye to cotton (triazine anchor). 

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