Alizarin Constitution

The first quinoline derivative obtained by the process (a) was the dye alizarin blue (Prud homme, 1877). f -Nitroaliza,rin was heated with glycerol and sulphuric acid. The constitution of the product was established by Graehe ... 

Grdbe (or Groebe), Carl (1841—1927). A German org chemist who established the constitution of naphthalene, anthracene and phthalic acid, etc. Co-synthesized with Carl Liebermann (1842-1914) alizarine Ref Hackb s Diet (1944), 386-R(Graebe) ... 

The acid crystallises from boiling acetic acid in yellow needles, which decompose indefinitely about 230° C. It is insoluble in water, but in alkali or sodium acetate it gives red solutions, and a yellow solution in concentrated sul dxuric acid. Its constitution has been ixroved by the following series of reactions, the final product being alizarin ... 

The mordant dyes cannot be left without first giving the pictorial development of the constitution of alizarin and Turkey red lakes. The structure of alizarin, 1,2-dihydroxyanthraquinone 9) ... 

Turkey Red.—Alizarin is the chief constituent of the coloring matter Turkey red, which has been known since ancient times and which was obtained from the root of the madder plant, Rubia tinctorum L. The substance is of special interest because the determination of its constitution was one of the early triumphs of organic chemistry and because it was the first natural dye to be synthetically prepared. The name is derived from the oriental name for the madder, viz., alizari. In the madder root it is present as a glucoside known as ruberythric acid, which, on hydrolysis by fermentation or by boiling with acids, yields glucose and alizarin. Alizarin is a solid which sublimes as orange red needles, m.p. 289°, insoluble in water but slightly soluble in alcohol. 

Synthesis, Graebe and Liebermann.— The determination the of constitution of alizarin and its synthetic preparation are both due largely to the work of Graebe and Liebermann in 1868. 

As will be seen, only these two mono-hydroxy compounds are possible. Now both of these mono-hydroxy anthraquinones yield alizarin by the introduction of a second hydroxyl group. The only constitution possible for a di-hydroxy anthraquinone obtained from both of these two mono-hydroxy anthraquinones is the 1-2-di-hydroxy compound. As alizarin is thus obtained the two hydroxyl groups in it must be in the 1-2 positions and not in the 2-3 positions. 

Only a few natural dyestuffs (indigo, alizarin, and purpurin) have been prepared synthetically, but the number of artificial dyestuffs is very large. Some of these, especially the phthalei ns and rosolic acid, seem to approach the natural dyestuffs in constitution, but the greater number belong to special classes, which are without analogue in either the animal or the vegetable kingdom. 

This group comprises most natural dyestuffs the constitution of some of these (alizarin and indigo) is known, and admits of systematic classification wfith just as much justice as the purely artificial dyestuffs and it would be reasonable to treat of the whole in a single chapter of natural dyestuffs. 

These mordant-dyeing properties are found in a much higher degree in the bodies obtained by action of nitrodiazo-compounds on salicylic acid (Germ. Pat. 44170, 16 Nov., 1887). The dyestuff from metanitrodiazobenzene and salicylic acid comes into commerce as Alizarin Yellow G, and produces a fine yellow lake with chromium oxide. The pure dyestuff crystallizes from alcohol in light yellow needles. M.P. about 230°. Its constitution may be expressed by the formula —... 

Only the /8-nitro-compound (of the constitution OH OH NO3) possesses technical interest. It may be obtained by treating alizarin, suspended in toluene or nitrobenzene, with nitrous acid, or by cautious nitration of alizarin dissolved in glacial acetic acid with nitric acid. 

This dyestuff is prepared by heating -nitroalizarin with glycerine and sulphuric acid. It is peculiar in so far that it possesses the lake-forming properties characteristic of the alizarin dyes, and is at the same time a weak base. Alizarin blue was discovered by Prud homme [28], and the determination of its constitution by Graebe [29] led to the synthesis of quinoline by Skraup from glycerine, nitrobenzene, and aniline. 

For the determination of metal cations, chelates are created with oxine (8-hydroxyquinoline), alizarine or benzoin, then extracted by organic solvents. In biochemistry, fluorescence has numerous applications for the quantification of proteins or nucleic acids by means of reagents which can affix with specificity to these compounds. This approach, sometimes very elaborate, in association with electrophoresis constitutes a more sensitive and less restricting method than detection by radioactive substrates. 

The reaction of alizarin with these fluorides was shown to be limited to the surface layer and each alizarin molecule was shown to take the place of two surface halide ions. This chemical reaction of alizarin with the surface of alkaline earth halides would constitute chemisorption according to our definition. 

Dyes may be classified according to their constitution, such as azo dyes, phthaleins, alizarines, etc., but from the standpoint of the dyer the more important classification is that which is based on the behavior of the dyes with fibers. Dyes are grouped in this way as substantive or direct, and adjective or mordant. Dyes are also classed as acidic and basic. In addition to the dyes belonging to these classes, there are a few, such as indigo and other Vat dyes, aniline black, and the so-called ingrain colors, which are produced by chemical reactions within the fiber. 

Quinones constitute a unique class of carbonyl compounds. They are cyclic conjugated diketones. The simplest example is 1,4-benzoquinone (eq. 7.44). All quinones are colored, and many are naturally occurring pigments that are used as dyes. Alizarin is an orange-red quinone that was used to dye the red coats of the British army during the American Revolution. Vitamin K is a quinone that is required for the normal clotting ofblood. 

In view of its constitution, Alizarin Blue (I) might be expected to display the characteristics of alizarin (page 96) and 8-hydroxyquinoline (page 335). This is not the case, as shown by the facts that it is neither soluble in alkali as is alizarin nor in dilute acids as is oxine. Probably Alizarin Blue is a chelate compound as represented in (la). Solutions can be prepared in dioxane, pyridine, acetic anhydride, concentrated sulfuric acid. These solutions react with strongly acid solutions of copper salts to produce a com-flower-blue crystalline precipitate, whose constitution as an inner complex compound is shown in (II). 

This schematic presentation is intended to show that the surface reaction leads to a silicon-fluorine bonding, in which the participating Si-atoms preserve their original phase association. Such surface reactions constitute the essence of a chemical adsorption (compare the surface reaction alumina-alizarin, page 97). In the familiar volatilization reaction of silica with concentrated hydrofluoric acid ... 

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