Oxidation of anthracene

In Europe, where an abundant supply of anthracene has usually been available, the preferred method for the manufacture of anthraquinone has been, and stiU is, the catalytic oxidation of anthracene. The main problem has been that of obtaining anthracene, C H q, practically free of such contaminants as carbazole and phenanthrene. Many processes have been developed for the purification of anthracene. Generally these foUow the scheme of taking the cmde anthracene oil, redistilling, and recrystaUizing it from a variety of solvents, such as pyridine (22). The purest anthracene may be obtained by azeotropic distillation with ethylene glycol (23). 

In the dyestuff industry, anthraquinone still ranks high as an intermediate for the production of dyes and pigments having properties unattainable by any other class of dyes or pigments. Its cost is relatively high and will remain so because of the equipment and operations involved in its manufacture. As of May 1991, anthraquinone sold for 4.4/kg in ton quantities. In the United States and abroad, anthraquinone is manufactured by a few large chemical companies (62). At present, only two processes for its production come into consideration manufacture by the Friedel-Crafts reaction utilizing benzene, phthahc anhydride, and anhydrous aluminum chloride, and by the vapor-phase catalytic oxidation of anthracene the latter method is preferred. 

The oxidation of an anthracene suspension in sulfuric acid conducted in the presence of cerium salts can serve as an example of mediated oxidation. In the bulk solution the Ce" ions chemically oxidize anthracene to anthraquinone. The resulting Ce ions are then reoxided at the anode to Ce". Thus, the net result of the electrochemical reaction is the oxidation of anthracene, even though the electrochemical steps themselves involve only cerium ions, not anthracene. Since the cerium ions are regenerated continuously, a small amount will suffice to oxidize large amounts of anthracene. 

In pulp and paper processing, anthraquinone (AQ) accelerates the delignification of wood and improves liquor selectivity. The kinetics of the liquid-phase oxidation of anthracene (AN) to AQ with NO2 in acetic acid as solvent has been studied by Rodriguez and Tijero (1989) in a semibatch reactor (batch with respect to the liquid phase), under conditions such that the kinetics of the overall gas-liquid process is controlled by the rate of the liquid-phase reaction. This reaction proceeds through the formation of the intermediate compound anthrone (ANT) ... 

For the liquid-phase oxidation of anthracene (AN) described in problem 5-17, Rodriguez and Tijero (1989) obtained the following values for the rate constants at 95°C in the two-step series reaction network ... 

Fig. 9. Indirect electrosynthetic process for the oxidation of anthracene to anthraquinone [10]. The charcoal column serves to remove organics which lead to corrosion and poisoning of the lead dioxide (Pb02) anode...

Photolytic. Oxidation of anthracene adsorbed on silica gei or aiumina by oxygen in the presence of UV-iight yieided anthraquinone. This compound additionally oxidized to 1,4-dihydroxy-... 

Early examples of electron transfer processes are shown in equations (2), (12), and (13). Birch in 1944 followed up the findings of Wooster, and demonstrated that Na metal and ethanol in ammonia reduce benzene, anisole, and other aromatics to 1,4-cyclohexadienes. Birch speculated about the mechanism of this reaction, but did not explicitly describe a radical pathway involving 55 (equation 87) until later, as described in his autobiography. Electron transfer from arenes was found by Weiss in 1941, who obtained crystalline salts of Ci4H]o from oxidation of anthracene. ... 

Fig. 8.20 Effect of scan rate on the cyclic voltammogram for the oxidation of anthracene (2.4 mM) at a platinum ultramicroelectrode in 0.6 M Et4NCI04-AN. Electrode radius 5 pm [62],...

Anthraquinone. Anthraquinone an important intermediate used extensively in the dye industry can be manufactured through the oxidation of anthracene.1041,1042 Almost all anthraquinone is currently produced by oxidation with Cr03 in the liquid phase (50-100°C) with selectivity better than 90% at complete conversion. 

Cerniglia, C. E. (1982). Initial reactions in the oxidation of anthracene by Curminghamella elegans. Journal of General Microbiology, 128, 2055-61. 

Anthraquinone is the primary product of the oxidation of anthracene over V2Os-based catalysts. The reaction is very selective and high yields of anthraquinone are possible due to its relatively high stability. An iron vanadate catalyst is used in the industrial process and yields of 80—90 mol. % are reported at 320—370°C. Phthalic anhydride, maleic anhydride and carbon oxides are the by-products. 

Although most of the experiments were carried out using p-xylene as substrate, several exploratory runs were made using other aromatic hydrocarbons. These are summarized in Table I. Maximum yields were not determined. Alkylnaphthalenes gave highly colored oxidates, from which only small amounts of naphthoic and naphthalic acids could be isolated. Oxidation of anthracene gave virtually quantitative yields of anthraquinone under extremely mild conditions (10). 

Anthraquinone is obtained by oxidation of anthracene using sodium bichromate plus sulfuric add, and is purified by dissolving in concentrated sulfuric acid at 130 Cl and pouring into boiling water, whereupon anthraquinone separates as pure solid, and is recovered by filtration, Further... 

Anthraquinone was produced in 96% yield from the oxidation of anthracene with TBHP in the presence of RhC (PPh1)3 catalyst (equation 93).266 Oxidation of cylic alkenes, e.g. cyclopentene, cyclohexene, cycloheptene, by TBHP in the presence of Rh2(OAc)4 results in the formation of a,/3-unsaturated ketones and allylic acetates as the major products (equation 94).267... 

It has been used to effect oxidation of anthracene and phenanthrene to quinones in > 70% yields. 

Anthracene is a polycyclic conjugated structure that cannot be fragmented into smaller units. The oxidants each have preferred points of oxidation on the conjugated rings, but the 9 and 10 positions are favored because of symmetry and stabilization of benzylic radicals. Rate constants for oxidation of anthracene by ROz, 102, and HO have been measured in solution or in vapor kox(R02) is 60 M 1 s 1 in chlorobenzene at 60°C (Mahoney, 1965) ... 

Addition of cerium salts accelerates the electrolytic oxidation of anthracene, naphthalene, and phenanthrene, which yield the corresponding quinones. The hydrocarbons may be in solution or in the form of a finely divided suspension. Anthracene, for example, is oxidised to Anthraqtjinone in 20 per cent, sulphuric acid anode current density is about 5 amps, per dm.2, and by the addition of 2 per cent, of cerium sulphate the current efficiency 8 is stated to reach nearly 100 per cent. 

The direct oxidation of arenes to quinones is a reaction with a limited scope [41], Only substrates that form stable quinones give good yields. For example, oxidation of anthracene to stable 9,10-anthraquinone with chromic acid is practiced on industrial scale. Such oxidations are believed to proceed through a series of one-electron oxidation/solvolysis steps. Yields and selectivity may be improved by using a strong one-electron oxidant such as cerium ammonium nitrate (CAN), as in the oxidation of phenanthrene to phenanthrenequinones (Eq. 9) [42]. 

Chou et al. [79] have studied the anodic oxidation of anthracene to anthraquinone in a slurry electrolyte containing both a Mn3+/Mn2" redox mediator and dodecylbenzenesulfonate (DBS) as surfactant. No reaction of anthraquinone is found in the absence of DBS. The main factors affecting the current efficiency of the process were sulfuric acid concentration, current density, particle size of anthracene, temperature, and concentrations of DBS and redox mediator. 

Oxidation of anthracene or higher acenes also occurs in the absence of a dye, since the same substrates act as sensitizers in singlet oxygenation [9c,42a]. These compounds react mainly at the mexo-positions of the aromatic nucleus [49a], but electron-donating groups have a strong directing effect when placed at the 1- and 4-positions (Sch. 33) [49b]. 

Eibes G, Moreira MT, Feijoo G et al (2007) Operation of a two-phase partitioning bioreactor for the oxidation of anthracene by the enzyme manganese peroxidase. Chemosphere 66 1744-1751... 

Air, often in the presence of a catalyst. Examples of this method are the preparation of phthalic anhydride from naphthalene by air and vanadium oxide (Wohl s method, page 171), and the analogous oxidation of anthracene to anthraquinone. In the latter case, anthracene which is not entirely pure can be used. 

However, in certain cases under photolytic conditions, spectra of the corresponding arylmercury radical cations 6 developed, whereas no mercuration occurred in dark [81] signifying collapse of the ArH +,Hg(TFA)2 radical ion pair 4, provides an alternative path way to Wheeland complex 2 and hence to ArHg(TFA) + 6. Arene radical cations can also be generated from arene and thallium(III) tris-(trifluoroacetate) in trifluoroacetic acid [82], but with a different mechanism proposed by Eberson et al. [83]. Oxidation of anthracene showed 9-trifluoroacetoxy and 9,10-bis(trifluoroacetoxy)anthracene [84, 85], benzo[a]pyrene, 7-methylbenzo-[a]pyrene and 12-methylbenzo[a]pyrene yielded radical cations of 7- and/or 12-trifluoroacetates [86], triptycene (9,10-dihydro-9,10-[l,2]benzanthracene) showed... 

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