Anthraquinone colorants synthesis

The synthesis of anthraquinone colorants may effectively be envisaged as involving two general stages. The first stage involves the construetion of the anthraquinone ring system and in the second phase the anthraquinone nucleus is elaborated to produce the desired strueture. Frequently, the latter involves substitution reactions, but group interconversion and further cyclisation reaetions may also... 

Heavy metals are widely used as catalysts in the manufacture of anthraquinonoid dyes. Mercury is used when sulphonating anthraquinones and copper when reacting arylamines with bromoanthraquinones. Much effort has been devoted to minimising the trace metal content of such colorants and in effluents from dyemaking plants. Metal salts are used as reactants in dye synthesis, particularly in the ranges of premetallised acid, direct or reactive dyes, which usually contain copper, chromium, nickel or cobalt. These structures are described in detail in Chapter 5, where the implications in terms of environmental problems are also discussed. Certain basic dyes and stabilised azoic diazo components (Fast Salts) are marketed in the form of tetrachlorozincate complex salts. The environmental impact of the heavy metal salts used in dye application processes is dealt with in Volume 2. 

From about 1930 onwards, developments in the field of naphthoquinone dyes concentrated on the use of naphthazarin and intermediates for the preparation of violet, blue, and green acid and disperse dyes [1]. More recently there has been interest in the synthesis and color and constitution properties of simple colored naphthoquinones, stimulated by the fact that such dyes have similar tinctorial properties to the anthraquinones but a smaller molecular size. The naphthoquinones provide a useful alternative to the anthraquinones for certain specialized applications, e g., as pleochroic dyes with improved solubility for liquid-crystal displays. As a result, research interest in these chromogens remains unabated, even though they have failed to make any major impact as textile dyes [2-8],... 

Disperse dyes vary in the type of chromophore present and include azo, anthraquinone, nitro, methine, benzodifuranone, and quinoline based structures. Examples of the first three types are given in Table 13.4, and representative of the latter three types are C.I. Disperse Blue 354, C.I. Disperse Yellow 64, and C.I. Disperse Red 356. Most disperse dyes have azo ( 59%) or anthraquinone ( 32%) structures. Azo disperse dyes cover the entire color spectrum, whereas the important anthraquinone disperse dyes are mainly red, violet, and blue. The azo types offer the advantages of higher extinction coefficients (emax = 30,000-60,000) and ease of synthesis, and the anthraquinones are generally brighter and have better photostability (lightfastness). The key weaknesses associated with the anthraquinone dyes are their low extinction... 

Determination of intermediates in dye synthesis (anthraquinone and derivatives), azo dyes in intermediates, products, coloring solutions and industrial effluents. Determination of aggregation number of textile dyes. Determination of food colors (e.g., of tartrazine type) in soft drinks Determination of monomers (aldehydes, acrylamide, acrylonitrile, isocyanates, methyl methacrylate, styrene, vinyl acetate) in final products and industrial effluents. Determination of initiators (azodiisobutyinitrile, benzoyt peroxide, cyclohexylperoxydicarbonate, laurylperoxide), inhibitors (hydroquinones, butylated hydroxyanisole, 4-f-butyl phenolsulphide, AAphenyt- -naphthylamine) and organo-tin stabilizers in PVC plastics... 

Alongside azo-dyes, dyes produced from anthraquinone represent one of the most important classes of dyestuffs. As to their color, anthraquinone dyes, with their blue and turquoise shades, complement the yellow to red azo dyes. In spite of their relatively complicated methods of synthesis, anthraquinone dyes find wide application, if their color-fastness and other qualities are superior to those of the competing azo dyes. 

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