Anthraquinone from anthracene

Sodium dichromate/acetic acid Anthraquinones from anthracenes... 

Anthraquinone has been produced commercially from anthracene by indirect electrooxidation based on the Cr3+/Cr6+ couple, cf. Fig. 9. 

Also important is the choice of a suitable redox system for the indirect electroreaction of particular substrates. For instance, toluene can be oxidized with Mn(III) or Ce(IV) to benzaldehyde, whilst with Cr(VI) benzoic acid is obtained. On the other hand, anthraquinone is commercially prepared from anthracene by employing chromic acid oxidation. 

The autoxidation mechanism by which 9,10-dihydroanthra-cene is converted to anthraquinone and anthracene in a basic medium was studied. Pyridine was the solvent, and benzyl-trimethylammonium hydroxide was the catalyst. The effects of temperature, base concentration, solvent system, and oxygen concentration were determined. A carbanion-initi-ated free-radical chain mechanism that involves a singleelectron transfer from the carbanion to oxygen is outlined. An intramolecular hydrogen abstraction step is proposed that appears to be more consistent with experimental observations than previously reported mechanisms that had postulated anthrone as an intermediate in the oxidation. Oxidations of several other compounds that are structurally related to 9,10-dihydroanthracene are also reported. 

The direct reaction of oxygen with the carbanion from dihydroanthracene does not seem likely. Russell (5) has indicated a preference for a one-electron transfer process to convert the carbanion to a free radical, which then reacts with oxygen to form an oxygenated species. Therefore, we considered a mechanism involving one-electron transfer to form a free radical from the carbanion, which would lead to the formation of anthraquinone and anthracene without having either the hydroperoxide or anthrone as an intermediate. 

Aliphatic aldehydes and ketones and also aliphatic-aromatic ketones can be converted into the corresponding hydrocarbons alkyl-phenols can be obtained from phenolic-aldehydes and -ketones p-hydroxy-benzophenone yields p-benzylphenol benzoin and benzil yield dibenzyl anthraquinone yields anthracene dihydride. 

Hydrogen atom transfer from anthracene, excited into its lowest excited singlet state, to anthraquinone impurity molecules creates a radical pair that strongly quenches the fluorescence from anthracene crystals. The reverse transfer rate constant, found from measurements of fluorescence intensity and its characteristic lifetime at different moments after the creation of the radical pair, varies from 106 to 10s s 1 in the range 110-65 K, kc = 4 x 104 s 1, TC = 60K. The kc values drops to 102 s 1 in the deuteroanthracene crystal [Lavrushko and Benderskii, 1978]. 

Artificial dyes in the laboratory of the Lancashire calico-printer John Lightfoot included his own invention of aniline black he also pioneered new methods for mordanting and the use of vanadium in aniline black printing.104A general account has been given of the role of rosaniline in the development of the synthetic dye industry.105 A paper on quinones focuses chiefly on the case of anthraquinone and the synthesis of alizarin from anthracene.106... 

Anthraquinone is being made at pilot plant scale from anthracene. The Ce3+/4+ couple is used with methane sulfonic acids. The steps involve anodic oxidation of Ce3+ and the use of Ce4+ outside the cell to convert naphthalene to napthaquinone, which is then converted to anthraquinone via a step involving butadiene. 

Figure 27. Application of flow cell and UV spectroscopy to study the reduction of aromatic compounds in iV,iV-dimethylformamide/0.1 M BU4NBF4 a) Plot of absorbance at = 556 nm and 732 nm, of the products obtained in the reduction of anthraquinone (T) and anthracene ( ), respectively, as the galvanostatic current to the flow cell is increased and a continuous flow of 5 mL min is maintained. The substrate concentrations are both 0.1 mM and the light path is 1 cm b) and c) The absorption spectra of the product obtained from reduction of anthraquinone and anthracene, respectively, when the galvanostatic current is increased above the maximum required for generating the radical anion. The current is increased from 2.0 to 2.8 mA in steps of 0.2 mA and the development in the spectra is indicated with arrows. Isosbestic points are also indicated. For anthraquinone, the spectra of the radical anion and the dianion could be resolved whereas for anthracene the dianion is protonated and spectra of the radical anion and 9,10-dihydroanthracen-9-ide could be resolved [65].

The direct synthesis of anthraquinone from phthalic anhydride and benzene has been reported to proceed over zeolite Beta [50] in a shape selective manner. In a conventional anthraquinone synthesis, anthracene is used as a feedstock for oxidation. Once there is a shortage of it in the market, additional anthracene could be produced by isomerization of its isomer, viz. phenanthrene. This, however, is not possible by direct isomerization of the trinuclear aromatic system but involves the partially (symmetrically) hydrogenated species. Consequently, isomerization of symmetrical octahydrophenanthrene to symmetrical octahydro-anthracene was studied by Song and Moffatt [51]. As sketched in Figure 3, a high yield of symmetrical octahydroanthracene can be obtained over zeolite H-mordenite (ngj/nyy = 8) at 250 °C (liquid phase, decalin as solvent). These examples show that (shape selective) catalysis on zeolites is more and more expanding into the conversion of polycyclic aromatics, and we foresee continued interest and success in this field of zeolite catalysis. 

Derivatives of anthracene are seldom prepared from anthracene itself, but rather by ring-closure methods. As in the case of naphthalene, the most important method of ring closure involves adaptation of Friedel-Crafts acylation. The products initially obtained are anthraquinones, which can be converted into corresponding anthracenes by reduction with zinc and alkali. This last step is seldom carried out, since the quinones are by far the more important class of compounds. 

The net result of the process is that impure or partly purified anthracene may be oxidized directly to anthraquinone. From tire standpoint of eouioment cost it does not matter whether two single catalytic converters... 

The use of mild oxidizing agents or operation under mild conditions usually results in products other than anthraquinone from the oxidation of anthracene. Tints, oxidation with tin oxide, manganese oxide, cerium acetate, or vanadium pentoxide in glacial acetic add results in the formation of a mixture of acetates.258 ... 

When mixtures of anthracene and phenanthrene, such as are obtained by removing carbazole from anthracene press cake by caustic fusion, arc oxidized, mixtures of phthalic anhydride and anthraquinone result. A separation of these valuable products is effected by washing out the acids with an alkali solution and recovering as sodium salts or as acids by addification subsequent to removal of anthraquinone by filtration. The products may be distilled or sublimed to separate from any unoxidized material that may be present. Maleic acid may also be present in the products to a small extent and is recovered with the phthalic anhydride from which it must be removed as an impurity.88... 

Alizarin, the dyestuff contained in madder, is made from anthracene, another coal tar product, by the action of "sodium bichromate and sulphuric acid to form antbraquinone this is traniSformed by the action of sulphuric acid into anthraquinone sulphonic acid, the sodium salt of which when fused with soda and a little potassium chlorate yields a compound of alizarin containing sodium, from which alizarin itself is made by the action of acid. 

These differences in ease of sulfonation (and correspondingly of desul-fonation, as discussed in a subsequent section) have formed the basis of a chemical method for the separation of mixtures of compounds otherwise hard to separate. The sulfonation of polycyclic hydrocarbons, such as anthracene or phenanthrene, occurs so easily that polysulfonates are formed even under such mild conditions that some of the hydrocarbon remains unsulfonated. For this reason, such sulfonations have been investigated relatively little and what data exist tend to be contradictory. Sulfonates derived from anthracene are usually prepared from anthraquinone, which yields fewer by-products than the hydrocarbon, although some disul-fonation does occur even with the usual industrial practice of partial sulfonation of the quinone. 

In the conversion of anthracene into anthraquinone, the para bond between the two carbon atoms involved in the oxidation is broken, but no change takes place in the benzene rings present in the compound. The synthesis of anthraquinone from phthalic anhydride confirms this view of its structure. When the anhydride is heated with benzene in the presence of a dehydrating agent, such as aluminium chloride, one molecule of water is lost and anthraquinone is formed —... 

Electrophilic substitution and other reactions of naphthalenes (alkylation, acylation, condensation and migration in acidic ionic liquids have been reported. Anthracene undergoes photochemical [4+4] cycloaddition reactions - in acidic chloroaluminate(III) ionic liquids. One interesting study ineluded a one-pot synthesis of anthraquinone from benzene giving a 94% yield. In general a much wider range of redox products are formed than occur in conventional solvents the strong Bronsted acidity of die ionic liquid induces protonation of anthracene, by residual traces of HCl, to form an anthracenium species which couples readily via photochemically driven electron transfer mechanisms. 

Alizarin blue was prepared from nitroalizarin, glycerol, and sulphuric acid by M. Prud homme, anthragallol (anthracene brown, i a 3-trihydroxy-anthraquinone) from pyrogallol and phthalic anhydride by C. Seuberlich, di- (or tetra-) azo dyes by Caro and Schraube, rhodamine from ammonium thiocyanate and chloracetic acid by M. Nencki, rocelline or echtrot (naphthalene sulphonic azonaphthol) by Roussin (1877) and Caro and Griess, and methylene blue by Caro (1877). ... 

The industrial importance of anthracene consists mainly in its use as a raw material in the production of anthraquinone small amounts are used in production of the tranquilizer benzoctamine, which is produced from anthracene and acrolein in a Diels-Alder reaction, followed by reductive amination of the aldehyde with methylamine. 

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