The use of anthraquinone

Anthraquinone glycosides are coloured substances, and are the active components in a number of crude drugs, especially with laxative and purgative properties. Anthraquinone aglycone increases peristaltic action of large intestine. A number of over the counter laxative preparations contain anthraquinone glycosides. The use of anthraquinone drugs, however,... 

Colouring matters which are neither acid nor basic are reduced and oxidised on the cotton itself. The resistance to reduction exhibited by certain azo-colouring matters, especially those formed directly on the fibre, is overcome by addition of very small quantities of suitable colouring matters or other reducing bodies, such as indulin scarlet, alizarin or anthia-quinone, which increase the activity of the hydrosulphite. The use of anthraquinone is preferred because it does not dye cotton, while addition of it in minimal quantity to the hydrosulphite solution and slight acidification with acetic acid yields a reagent (hydrosulphite B X) which causes reduction in every case. 

There are numerous references in the Patent Literature (72—76) to the use of anthraquinone and similar compounds as photoinitiators of polymerization or crosslinking required in the preparation of printing plates etc, although apparently little is known of the detailed reaction mechanisms. One literature report (77) described the polymerization of aqueous methyl acrylate by sodium anthraquinone-2-sulphonate in the presence of chloride ions, with a conclusion that the initiating species are chlorine atoms. 

The use of anthraquinone-2,6-disulphonate as mediator is easily possible since P. mirabilis and P. vulgaris possess a DMSO reductase (Scheme 4). Its activity depends on the growth conditions (Table 18), (47,62). 

Considerable interest has been shown in the use of anthraquinone in wood pulping operations. The optimal yield of pulp and pulp viscosity at a given Kappa number was obtained with 0.25 M-NaOH. The rate of delignification was... 

Anthraquinone can be sulfonated, nitrated, or halogenated. Sulfonation is of the greatest technical importance because the sulfonic acid group can be readily replaced by an amino or chloro group. Sulfonation with 20—25% oleum at a temperature of 130—135°C produces predominandy anthraquinone-2-sulfonic acid [84-48-0]. By the use of a stronger oleum, disulfonic acids are produced. The second sulfonic acid substituent never enters the same ring a mixture of 2,6- and 2,7-disulfonic acids is formed (Wayne-Armstrong rule). In order to sulfonate in the 1-, 1,5-, or 1,8-positions, mercury or one of its salts must be used as a catalyst. 

S oda—Anthraquinone. A few mills worldwide use soda pulping of hardwoods. In such cases, the addition of anthraquinone is immediately justifiable in terms of increased yield and upgraded pulp quaHty. The conversion of existing kraft mills is not as simple because AQ contributes no alkalinity to the process as sulfide does, and most kraft causticizing systems would have to be expanded by about 33%. This conversion is probably not justifiable in terms of the yield gain. The greatest benefit from AQ is for new mills in which expenditures for air pollution abatement devices can be reduced. 

In the first case (22), almost stoichiometric amounts of sulfuric acid or chlorosulfonic acid are used. The amine sulfate or the amine chlorosulfate is, first, formed and heated to about 180 or 130°C, respectively, to rearrange the salt. The introduction of the sulfonic acid group occurs only in the ortho position, and an almost quantitative amount of l-aminoanthraquinone-2-sulfonic acid is obtained. On the other hand, the use of oleum (23) requires a large excess of SO to complete the reaction, and inevitably produces over-sulfonated compound such as l-amino-anthraquinone-2,4-disulfonic acid. Addition of sodium sulfate reduces the byproduct to a certain extent. Improved processes have been proposed to make the isolation of the intermediate (19) uimecessary (24,25). 

Alizarin. There is only one significant plant anthraquinone dye, alizariu [72-48-0] (Cl Natural Red 6, 8, 9,10, 11, and 12 Cl 75330). In ancient times, alizaria was the preferred red dye. Cloth dyed with it has been found in Egyptian tombs dating 6000 years ago. The dye is found in the madder plant, a member of the Rubiaceae family. In 1944 about 35 species of this plant were known (1), but the use of more sophisticated analytical methods led to the detection of many more species by 1984 the number had increased to 50 (2). Of these, tinctorum and R peregrina yield the greatest amount of dye,... 

The valence-bond approach may be used to provide a qualitative account of the /lmax values, and hence the hues, of many dyes, particularly those of the donor acceptor chromogen type. The use of this approach to rationalise differences in colour is illustrated in this section with reference to a series of dyes which may be envisaged as being derived from azobenzene, although in principle the method may be used to account for the colours of a much wider range of chemical classes of dye, including anthraquinones (see Chapter 4), polymethines and nitro dyes. 

The use of the stannylquinones 81 results in the regioselective formation of 1,4-naphthoquinones or 9,10-anthraquinones 82 [40]. Highly-oxygenated angularly-fused polycyclic aromatic compounds are prepared by the ring enlargement [41]. (Scheme 29)... 

HPLC ESI MS is also a useful tool in the analysis of non-anthraquinone red dyestuffs. The use of this technique allows the identification of carthamin as the main colour component of safflower.[34] Ten species of the genus Alkanna are extracted with hexane, and dissolved in water-methanol solution after evaporation. [47] Ammonium formate buffer (pH 3.0) was used as the mobile phase modifier. In the preparations, alkannin and many hydroxynaphthoquinones (alkannin derivatives) were identified by comparison of retention times, as mass spectra (in the NI mode) for all compounds consisted only of quasi-molecular peaks. 

Catalytic amounts of this addend (4 equiv relative to Cu) increase the selectivity of the allylic oxidation when TBHP is used as the oxidant. No change was observed with terf-butyl perbenzoate. This observation suggests a dichotomy in the mechanism of this reaction when using the two oxidants. Furthermore, in the absence of anthraquinone, a small negative nonlinear effect (78) is observed while in its presence, a small positive nonlinear effect appears. The reasons for this reversal are not clear, although the authors observed that low enantiopurity catalysts lead to turbid... 

Anthraquinone dyes are second only to azo dyes in importance as disperse dyes and are predominant in the red, violet, blue and blue-green sectors [14]. Because anthraquinone disperse dyes are relatively expensive to manufacture, successful attempts were made to replace some of them with technically equivalent and more economical products [15]. The replacement process has been most successful in the red region using, for example, heterocyclic azo dyes and novel chromogens. The brilliance of the anthraquinones with their narrow spectral absorption bands is difficult to attain with other structures, however, as is their high light fastness and chemical stability. The development of anthraquinone disperse dyes is included in a review by Dawson [16]. 

Concentrated sulphuric acid here performs the same function in the first phase as does aluminium chloride, and by the use of the acid the anthraquinone derivative is obtained in a single operation. The synthesis of quinizarin, described above, provides a preparative illustration of this elegant reaction ... 

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