Anthracene anodic oxidation

PbOj, 40 155-156 oxygen evolution, 40 109-110 reaction, history, 40 97 solid oxide fuel cells, 40 149-150 Anodic oxidation, ammonia, 38 13 1,8-ANS inclusions, 32 453 54 Antagonism, 25 338, 339 Anthracene... 

Similar results were obtained in the anodic oxidation of 9,10-dimethyl-anthracene S3-). 

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. 

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. 

The 1,2- and 1,4-addition reactions have been observed also for alkyl-substituted aromatics, but the yields are often low, in particular for benzene derivatives, owing to competing side-chain substitution reactions. Examples include the addition of MeOH to methyl-substituted benzenes [38-42], naphthalenes [43], and anthracenes [43,44]. In a similar fashion, the anodic oxidation of 1,3-dienes in MeOH [45,46] results in mixtures of 1,2- and 1,4-addition products accompanied by substitution products and methoxy-containing dimers and trimers [46]. Styrenes are oxidized in MeOH to the 1,2-addition product together with products formed by dimerization-addition [47,48]. Oxidation of allenes results in most cases in complicated product mixtures resulting from single and double addition reactions [49-52]. 

Anodic oxidation of anthracene in MeCN containing (CF3C0)20 (to remove water and suppress hydroxylation) leads to the formation of the acetamidation product in 85% yield [159]. Results obtained by cyclic voltammetry supported the mechanism shown in Eq. (47). 

Anodic oxidation of n-alkanes in acetonitrile results in mixtures of A -s-alkylacetamides but skeletal rearrangement of the intermediate i-carbenium ions is not observed. Aromatic compounds can undergo direct acetamidation in the ring. Thus, acetophenone, which normally undergoes electrophilic aromatic substitution at the meta position, affords the o- and p-acetamides (Scheme 44). Anthracene is cleanly converted into the acetamide (84) when the reaction is performed in the presence of TFAA as water scavenger (equation 41). ... 

Millington (1969) oxidized anthracene anodically in acetonitrile containing Et4NBr, and, on the basis of the effect of the applied potential on yields of bromination products, attributed the formation of 9-bromo- and 9,10-dibromoanthracene to reaction of bromide ion with either the cation radical or dication of anthracene. The conclusion must be treated with caution, since the oxidation potential of bromide ion is much lower than that of anthracene. 

The analogies which exist between anodic oxidation and cathodic reduction reactions of aromatic compounds are extensive radicals formed from radical cations by chemical reaction can be further oxidised by other radical cations, i.e. by an overall disproportionation mechanism. Thus the formation of trans 9,10-dihydroxy 9,10-diphenyl anthracene on the addition of water to a solution of 9,10-diphenyl anthracene... 

Anodic oxidation of various aromatic compounds Uke anisole, mesitylene, and fused aromatic compounds like naphthalene and anthracene was carried out in various ionic liquids such as [BMIM][PF6] and [BMIM][NTf2] to provide the corresponding dimmers in moderate to good yields [25]. Under similar conditions, anodic oxidation of 1,2-dimethoxybenzene leads to the corresponding trimer as shown in Scheme 7 [25]. 

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. 

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...

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. 

Vanadium2 compounds may be employed as catalysts in oxidation, and reduction processes. Por example, anthracene is oxidised to anthraquinone with a lead anode in 20 per cent, sulphuric acid which contains 3 per cent, of vanadic acid. Aniline under similar conditions may be oxidised to benzoquinone, and the latter substance can be efficiently reduced to hydroquinone. Azobenzene and azoxybenzene are stated to give a good yield of benzidine... 

At anodic potentials Anthracene oil, i.e. cresote, formed insoluble, insulating films on current-carrying electrodes (Figure 4). Figure 4a. shows oxidation traces from three successive cyclicvoltammograms with switching potential,... 

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