Alizarine properties

A chemical process occurs involving the formation of a new substance with corresponding energetic ground state N (Fig. 14, 15/V). For instance, on aluminium oxide or silica gel layers in the presence of oxygen, anthracene initially yields anthra-quinone, that is then oxidized further to yield 1,2-dihydroxyanthraquinone [4, 5]. Alizarin and chrysazin are also formed depending on the properties of the aluminium oxide used [6]. 

In 1871 Graebe and Liebermann discovered that alizarin (6.2) could be applied to wool by mordant dyeing after sulphonation to produce the 3-sulphonic acid (6.28). This dye is still listed in the latest revision of the Colour Index as a commercial product [11]. Although many sulphonated polyhydroxyanthraquinones have been examined, few remain in current use. Another, and more important, classic dye that continues in commercial use as an acid dye is Cl Acid Blue 45 (6.29). This dye was discovered in 1897 by Schmidt and can be made from anthrarufin (6.13) by disulphonation, subsequent dinitration and reduction. The dye gives an attractive blue on wool with good all-round fastness properties. 

This peculiar property of dyeing on metallic mordants has as yet had no satisfactory explanation. If cotton mordanted with alumina or oxide of iron is placed in an alizarin bath, the lake is precipitated and enters into intimate combination with the fibre. 

Many dyestuffs form insoluble lakes with metallic oxides, but the property of combining with mordants on the fibre is peculiar to a fe f. Insoluble lakes may be obtained from the cosines and from all oxyanthraquinones, but the former class of bodies cannot be fixed on mordants, and of the latter only derivatives of alizarin possess this property. 

The dyes prepared from salicylic acid mostly possess the property of dyeing on alumina, iron, and chromium mordants, in a similar manner to alizarin. 

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 —... 

Of the numerous hydroxyl derivatives of anthraquinone, only those which have two hydroxyl-groups in the 1, 3-position to the carbonyl-group of anthraquinone are capable of dyeing upon mordants. In other words, only alizarin and its derivatives possess this property. As the number of anthraquinone derivatives is very large, we must necessarily confine ourselves to those of technical value. 

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. 

The great importance of a large number of the natural dyestuffs is based on the property which they possess of forming firmly-adherent lakes with metallic oxides. They are, like alizarin, adjective dyestuffs. 

The following topics have not been considered in this section metal complexes of sulfonated 2,2 -bipyridine [43] and alizarin [44], water-soluble porphyrins and cy-dopentadienyl ligands [45], and metal complexes of sulfonated phenanthroline derivatives [46], Also P,N-bidentate phosphines [47], of which coordination properties await further study, have not been discussed here. 

CAS 2666-17-3 EINECS/ELINCS 220-201-9 Synonyms Alizarine blue A 2-Anthracenesulfonic acid, 1-amino-9,10-dihydro-4-(p-(N-methylacetamido) anilino)-9,10-dioxo-, monosodium salt Cl 62130 Classification Azobenzene Empirical C23HisN3Na06S Properties M.w. 487.45... 

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