Quinizarin

The purple quinizarin solution is next saturated with carbon dioxide and the precipitated quinizarin again filtered. The product is then boiled with 5 1. of a 10 per cent solution of sodium carbonate until it appears black (probably the mono-sodium salt) to dissolve the last traces of purpurin. The mixture is cooled to room temperature, filtered, and the precipitate boiled with 5 1. of 5 per cent hydrochloric acid to liberate the quinizarin. The mixture is again cooled to room temperature and the final product filtered, washed with cold water and dried at 100°. 

The yield is 147-160 g. (68-74 per cent of the theoretical amount). It sinters at 190-191° and melts at 199-200° (corr.). A sample twice recrystallized from glacial acetic acid melted at 200-202° (corr.) (Note 3). The crystal form of this product compares very favorably with that of quinizarin of the highest purity, as observed under the microscope. 

An enameled bucket placed on a Fletcher radial burner serves well for this purpose. 

The purple color end point is not sharp, but as soon as the red hue of the mixture has distinctly changed toward purple, this point is considered reached. A variation of 5-10 cc. either way has little effect, but a large excess gives a large alkali-insoluble residue. 

Quinizarin has been prepared by heating /)-chlorophenol, phthalic anhydride, and sulfuric acid by heating hydroquinone with phthalic anhydride - by heating hydroquinone, phthalic anhydride and c.i . sulfuric acid by oxidizing anthraquinone 

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Materials. Beside inorganic materials (eg, barium chloride/fluoride crystals, doped with 0.05% samarium), transparent thermoplasts are preferred for the PHB technique, eg, poly (methyl methacrylate) (PMAIA), polycarbonate, and polybutyral doped with small amounts of suitable organic dyes, organic pigments like phthalocyanines, 9-arninoacridine, 1,4-dihydroxyanthraquinone [81-64-1] (quinizarin) (1), and 2,3-dihydroporphyrin (chlorin) (2). 

One of tfie most important applications of 4-chloiophenol is in the synthesis of derivatives of quinizarin [81-64-17, anthraquinone dyes (see Dyes,... 

In the benzene and naphthalene series there are few examples of quinone reductions other than that of hydroquinone itself. There are, however, many intermediate reaction sequences in the anthraquinone series that depend on the generation, usually by employing aqueous "hydros" (sodium dithionite) of the so-called leuco compound. The reaction with leuco quinizarin [122308-59-2] is shown because this provides the key route to the important 1,4-diaminoanthtaquinones. 

Dihydroxyanthraquinone. This anthraquinone, also known as quinizarin [81-64-1] (29), is of great importance in manufacturing disperse, acid, and vat dyes. It is manufactured by condensation of phthalic anhydride (27) with 4-chlorophenol [106-48-9] (28) in oleum in the presence of boric acid or boron trifluoride (40,41). Improved processes for reducing waste acid have been reported (42), and yield is around 80% on the basis of 4-chlorophenol. 

In this reaction, three steps, ie, acylation, cyclization, and replacement of the chlorine atom by the hydroxyl group, take place simultaneously in concentrated sulfuric acid. In the course of cyclization 2,7-dichlorofluoran (31) may be formed as a by-product presumably through the carbonium ion (30) ihustrated as follows. The addition of boric acid suppresses this pathway and promotes the regular cyclization to form the anthraquinone stmcture. The stable boric acid ester formed also enables the complete replacement of chlorine atoms by the hydroxyl group. Hydrolysis of the boric acid ester of quinizarin is carried out by heating in dilute sulfuric acid. The purity of quinizarin thus obtained is around 90%. Highly pure product can be obtained by sublimation. 

Hydroquinone may also be used in place of 4-chloroplienol. In this case an aluminum chloride—sodium chloride melt is usually employed. However, the yield is not satisfactory (43). It has also been reported that the reaction of hydroquinone with substantially stoichiometric phthaUc acid dichloride in the presence of anhydrous aluminum chloride in moderately polar solvents, such as nitrobenzene at around 100°C gives quinizarin (44). The reported yield is 65% after purification by crystallization from toluene. 

Quinizarin Derivatives. Acid dyes derived from the reaction products of quinizarin with aromatic or aUphatic amines are important commercially and predominant in number. They are prepared from leucoquinizarin (127), the reduced form of quinizarin (29). The dominant stmcture of leiicoqiiinizarin is the 2,3-dihydrotautomer (128) (132). 

Quinizarin (l,4-dihydroxy-9,10-anthraquinone) (9.5), PK2 11.18. Crystd from glacial acetic acid. 

Fluorimetry is generally used if there is no colorimetric method sufficiently sensitive or selective for the substance to be determined. In inorganic analysis the most frequent applications are for the determination of metal ions as fluorescent organic complexes. Many of the complexes of oxine fluoresce strongly aluminium, zinc, magnesium, and gallium are sometimes determined at low concentrations by this method. Aluminium forms fluorescent complexes with the dyestuff eriochrome blue black RC (pontachrome blue black R), whilst beryllium forms a fluorescent complex with quinizarin. 

In 1963, Bloom and Hutton suggested5 the structure of leuco quinizarin in solution as 9,10-dihydroxy-2,3-dihydro-l,4-anthraquinone (9a). In 1981, Kikuchi and colleagues6 confirmed the structure by means of H- and... 

Two structures 9a or 9b are possible for leuco quinizarin (9). Bloom and Hutton5 have proposed the structure of 9 to be 9a by comparing the chemical shift of methylene protons with those of leuco naphthazarin (3.05 ppm) and leuco naphthoquinone (3.08 ppm). However, based on UV spectra and chemical reactivity, Egerton and CO-workers7 and Greenhalgh8 independently suggested an equilibrium mixture of 9a and 9b in solution. 

It is well known that quinizarin (22) is alkylaminated in air to give a mixture of l-alkylamino-4-hydroxyanthraquinone (23), l,4-bis(alkylamino)-anthraquinone (24), and 2-alkylaminoquinizarin (25) (Scheme 7). The reaction conditions affect the ratio of these products. In a nitrogen atmosphere, or in the presence of sodium dithionite as reducing agent, the main amination product is 24. The solvent effects of the reaction of leuco... 

The alkylamination of quinizarin (22) in the presence of copper salts has been studied by Matsuoka and co-workers.16 The reaction proceeds via oxidation by copper ion of 22 to quinizarinoquinone (29). 2-Alkylamino-quinizarin (25) was obtained in quantitative yield. The 1,2-ring-closure product (30) is obtained by the reaction of 22 with ethylenediamines in the presence of copper ions17 (Scheme 9). 

An important route to 1,4-diaminoanthraquinones, represented by structure 78, is illustrated in Scheme 4.6. Quinizarin (75) is first reduced to leucoquinizarin, which has been shown to exist as the diketo structure 77. Condensation of compound 77 with two moles of an amine, followed by oxidation leads to the diaminoanthraquinone 78. Boric acid is a useful catalyst for this reaction, particularly when less basic amines are used. 

Wool dyed with Rubia tinctorum and Galium verum Alizarin, quinalizarin, purpurin, xanthopurpurin, purpuroxanthin dimethyl ether, munjistin, rubiadin, nordamnacanthal, anthragallol, kermesic acid, hystazarin, emodin, quinizarin HCI/MeOH/ h2o A H20 B ACN with AcOH or FA 250 nm/ESI ( ) HPLC optimization... 

Standards, Aubusson tapestry from nineteenth century Gallic acid, dihydroxybenzoic acids, carminic acid, alizarin, purpurin, xanthopurpurin, quinizarin, emodin, morin, quercetin, luteolin, apigenin, rhamnetin, hystazarin, anthragallol HCI/MeOH/H20, DMSO A ACN B H20 with HCOOH 256 nm/ESI (+)... 

Although anthraquinone is the starting point for the preparation of many derivatives, involving substitution and replacement reactions, certain compounds are obtained directly by varying the components in the above synthesis. Thus, for example, replacement of benzene with methylbenzene (toluene) leads to the formation of 2-methylanthraquinone. A particularly important variation on the phthalic anhydride route is the synthesis of 1,4-dihydroxyanthraquinone (6.6 quinizarin) using 4-chlorophenol with sulphuric acid and boric acid as catalyst (Scheme 6.3). The absence of aluminium chloride permits hydrolysis of the chloro substituent to take place. 

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