Chemical Constitution and Synthesis

Cationic functionality is found in various types of dyes, mainly in cationic azo dyes and methine dyes, but also in di- and triarylcarbonium dyes (Section 2.6) and solvent dyes (Section 3.10). Due to their importance, in this book the group of cationic dyes is divided into azo dyes and methine dyes. 

Basic dyes of the azo class were among the earliest known synthetic dyes. They were used originally for dyeing cotton mordanted with tannin and potassium antimonyl tartrate and wool from neutral solution. They continue to have minor importance for dyeing leather, paper, plastics, and waxes, and as constituents of graphic arts colors. 

The preparation of the first cationic azo dye, Vesuvin, was described by C. Martius in 1863. It is obtained by coupling diazotized m-phenylcncdiamine to an excess of the same amine. An analogous dye from toluylenediamine was reported by P. Gries in 1878. Chrysoidines, coupling products of aniline or toluidines to m-phenylenediamine or toluylenediamine, were reported by H. Caro in 1875 and O. N. Witt in 1876. 

When polyacrylonitrile fibers appeared on the market, an intense research effort in the area of cationic azo dyes was stimulated worldwide at all the leading dye plants. These materials now occupy a place of importance in all significant product lines. 

Azo dyes with several cationic charges, which are substantive dyes for cellulose, are increasingly being used for coloring bleached sulfite cellulose. 

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Due to the great variability of different types of cationic azo dyes chemical constitution and synthesis are outlined together in this section. The general synthesis of azo dyes is described in Section 2.1. 

To provide an overview chemical constitution and synthesis are combined in this section. The various application media for metal-complex dyes are a further ordering principle, which generates overlap of some sections with reactive dyes (Section 3.1), leather dyes (Section 5.1), and paper dyes (Section 5.3), demonstrating the typically complex interrelationship of constitution and application of dyes. 

Callow R. K. and Johnson N. C. (1960) The chemical constitution and synthesis of queen substance of honeybees (Apis mellifera L.). Bee World 41, 152-153. 

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