Anthraquinone compounds

Azo and anthraquinone compounds comprise the two principal stmctural types which are used as disperse dyes. Other compounds used to a much lesser extent include methines, cyanostyryls, hydroxyquinophthalones, and ifitrodiarylarnines. 

In order to develop the dyes for these fields, characteristics of known dyes have been re-examined, and some anthraquinone dyes have been found usable. One example of use is in thermal-transfer recording where the sublimation properties of disperse dyes are appHed. Anthraquinone compounds have also been found to be usehil dichroic dyes for guest-host Hquid crystal displays when the substituents are properly selected to have high order parameters. These dichroic dyes can be used for polarizer films of LCD systems as well. Anthraquinone derivatives that absorb in the near-infrared region have also been discovered, which may be appHcable in semiconductor laser recording. 

Table 15. Acute Toxicity Data for Some Anthraquinone Compounds ...

In a related series of 1,2,4-trisubstituted anthraquinone compounds, the effectiveness of various polar and nonpolar substituents to improve on the low heat fastness of 2-amino-1,4-dihydroxyanthraquinone (3.184 R = H) was examined (Table 3.50). Short-chain alkyl groups (methyl, ethyl) and even the pyranylmethyl ether are relatively ineffective but hydroxyalkyl, cyclohexyl, benzyl and morpholinylethyl groups show moderate increases. Further improvement is given by phenyl, pyridylmethyl and morpholinylpropyl. Outstandingly effective, however, are the benzothiazolyl, dodecylphenyl and fluoro-methylphenyl groupings. 

Formation of C—C links in the anthraquinone molecule, especially substitutions with aryl moieties, proceed via copper-catalyzed nucleophilic exchange of halogenated anthraquinone compounds. These methods include dimerization of 1 -aminoanthraquinone. 

N.A. Cinnamic acid, gallic acid, emodin, rhein, rhein anthrones, catechin, anthraquinone compounds, tannin, calcium oxalate.99-100-107-510-511 Treat diarrhea, stimulate appetite, chronic constipation, laxative, cathartic. 

Anthocyanosides Anthraquinone Anthraquinone derivatives Anthraquinone glycosides Anthraquinone compounds Anthraquinones... 

A + RCH2OH - AH. + RCHOH At low concentrations of photoexcited dye and in competition with radiationless deactivation processes the radicals can react with oxygen to form additional radicals and/or hydrogen peroxide. At higher concentrations electron transfer reactions to semi-reduced (A ) and semi-oxidized (A +) anthraquinone compounds can occur which in turn undergo secondary reactions. 

More recently, a new class of covalent-linked calix[4]pyrrole-anthraquinone compounds (29-31) have been introduced by Sessler s group [48], These are considered to be powerful naked eye sensors for fluoride, chloride and dihydrogen phosphate ions in dichloromethane. The most pronounced colour change was observed upon the addition of the fluoride anion into a solution of the receptor 30 in dichloromethane. The addition of bromide, iodide or nitrate anions did not lead to significant colour changes. 

Multiply hydroxylaied benzene derivatives react with phthalic acid anhydride and a suitable activator, when heated, in a double C acylation. Evidently, under these conditions, the activating influence of the additional OH groups is important even after the first acyl group has been introduced. The resulting doubly acylated product is a 9,10-anthraquinone. Compounds of this type are important as dyes ... 

The reduction of azo compounds using sodium hydrosulfite (Na2S204) and NaOH is an important reaction, as it provides an indirect method for the amination of phenols and naphthols (Fig. 13.49). The reduction of nitro groups in anthraquinone compounds works best when a mild reducing agent (e.g., sodium hydrosulfide, NaSH) is used. In this way one avoids reducing the quinoid system. 

Fig. 13.52. Amination reactions involving benzene and anthraquinone compounds.

In special cases, chlorination is brought about by replacement of a sulfonic group by chlorine. This reaction is particularly important with anthraquinone compounds, but it is also known in the benzene series (see page 236). 

These are used to color silk, wool, and other animal fibers, or nylon (polyamide) when high wet-fasmess is needed. Such dyes include monoazoic, diazoic, triphenylmethane, and anthraquinone compounds. Acid Yellow 23, Acid Black 48, Acid Black 63, and Acid Violet 17 (triphenylmethane derived Figure 16) were reported in the literature, mainly before 1985. Acid Yellow 61 (Supramine Yellow GW), Acid Red 359 (Neutrichrome Red SGN), and Acid Red 118 (Supramine Red GW), each tested in 5% petrolatum and removed after 3 days, were positive for skin... 

Dyes are chemical compounds that impart color to plastic compounds. These dissolve in the host polymer and are therefore not present as discrete particles. Dyes are typically azo or anthraquinone compounds. 

Compounds 1-5 are anthraquinones. Compounds 1 and 4 are structurally similar to emodin. Structures 3 and 5 are glucoside derivatives of 2 and 4. 

Several herbal texts caution against the use of anthra-quinone-containing botanicals in pregnancy due to mutagenic activity of some anthraquinone compounds, but these texts also note that animal tests of various anthraquinones show no teratogenic or embryotoxic activity (Brinker 2001 De Smet 1993 ESCOP 2003). 

In addition to conversion to anthraquinones, compounds such as emodin anthrone can be coupled by free-radical processes to produce a series of complex dimers such as hypericin (77) and fagopyrin (78) (Fig. 6.20) (Brockman and Lack-ner, 1979 Scott, 1967). 

Anionic dyes are selected from the group consisting of nitroso compounds, nitro compounds, azo compounds, stilbenes, triaryl-methane compounds, xanthene compounds, quinoline compoimds, thiazole compounds, azine compounds, oxazine compoimds, thi-azine compounds, aminoketone compounds, anthraquinone compounds, indigoid compounds and phthalocyanine compoimds. 

Figure 9.17 Distance-dependence of in some donor-acceptor molecules. Plots of log( et) edge-to-edge distances in a variety of linked donor-acceptor systems, (a) Forward(D) and reverse (x) electron-transfer rate constants for zinc porphyrin-anthraquinone compounds in butyronitrile. (b) Forward ( ) and reverse (x) electron-transfer rate constants for dimethoxynaphthalene-dicyanoethylene compounds in benzene, compared with the forward rate constants for three anthracene-dimethylaniline systems (V) and four analogous pyrene-dimethylaniline molecules (-I-), all in acetonitrile. From J.S. Connolly and J.R. Bolton, in Ref. [21,e, p. 322].

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