Anthracene, oxidation reactions

Nucleophilic Trapping of Radical Cations. To investigate some of the properties of Mh radical cations these intermediates have been generated in two one-electron oxidant systems. The first contains iodine as oxidant and pyridine as nucleophile and solvent (8-10), while the second contains Mn(0Ac) in acetic acid (10,11). Studies with a number of PAH indicate that the formation of pyridinium-PAH or acetoxy-PAH by one-electron oxidation with Mn(0Ac)3 or iodine, respectively, is related to the ionization potential (IP) of the PAH. For PAH with relatively high IP, such as phenanthrene, chrysene, 5-methyl chrysene and dibenz[a,h]anthracene, no reaction occurs with these two oxidant systems. Another important factor influencing the specific reactivity of PAH radical cations with nucleophiles is localization of the positive charge at one or a few carbon atoms in the radical cation. 

The use of certain vanadium compounds as catalysts has been increasing. Vanadium oxy trichloride is a catalyst in making ediylene-propylene rubber. Ammonium metavanadate and vanadium pentoxide aie used as oxidation catalysts, particularly in the production of polyamides, such as nylon, in the manufacture of H>S04 by the contact process, in the production of phdialic and maleic anhydrides, and in numerous other oxidation reactions, such as alcohol to acetaldehyde, anthracene to anthraquinone, sugar to oxalic acid, and diphenylamine to carbazole. Vanadium compounds have been used for many years 111 die ceramics field for enamels and glazes. Colors are produced by various combinations of vanadium oxide and silica, zirconia, zinc, lead, tin, selenium, and cadmium. Vanadium intermediate compounds also are used in the making of aniline Mack used by the dye industry... 

The photo-oxidation of n-butane has been modelled by ab initio and DFT computational methods, in which the key role of 1- and 2-butoxyl radicals was confirmed.52 These radicals, formed from the reaction of the corresponding butyl radicals with molecular oxygen, account for the formation of the major oxidation products including hydrocarbons, peroxides, aldehydes, and peroxyaldehydes. The differing behaviour of n-pentane and cyclopentane towards autoignition at 873 K has been found to depend on the relative concentrations of resonance-stabilized radicals in the reaction medium.53 The manganese-mediated oxidation of dihydroanthracene to anthracene has been reported via hydrogen atom abstraction.54 The oxidation reactions of hydrocarbon radicals and their OH adducts are reported.55... 

V. Catalysts.—Electrolytic oxidation reactions are often facilitated by the presence of catalysts capable of existing in two valence stages examples of such oxygen carriers are cerium, chromium, manganese and vanadium ions. Their action is probably similar to that previously described for hydrogen carriers. These catalysts have been used to facilitate the oxidation of toluene to benzaldehyde or benzoic acid, of toluene sulfonamide to saccharin, and of anthracene to anthraquinone. 

Some PAHs are degraded by oxidation reactions that have been measured in the dark (to eliminate the possibility of photodegradation). Korfmacher et al. (1980) found that, while fluorene was completely oxidized, fluoranthene and phenanthrene were not oxidized, and benzo[a]pyrene and anthracene underwent minimal oxidation. These compounds were tested adsorbed to coal fly ash the authors stated that the form of the compound (adsorbed or pure) and the nature of the adsorbent greatly affected the rate and extent of oxidation. 

The second of these patents 100 deals with the oxidation of toluene, naphthalene and anthracene and refers specifically to the restricted use of certain vanadates of tin and bismuth which have been discovered to possess particular activity in catalyzing oxidation reactions. Examples illustrating the preparation and temperature ranges for different catalysts are given. 

While the overall reaction of anthracene oxidation to form anthra-quinone as shown above involves the interaction of three atoms of oxygen per molecule of hydrocarbon, the actual mechanism of the catalysis is more or less obscure. From the observations of Senseman and Nelson86 the vanadium oxide catalysts function by being alternately reduced to a lower oxide by the hydrocarbon and oxidized to the pentoxide by the oxygen of the air used. Thus ... 

The optically active benz[a]anthracene oxides (89) and (90) have been synthesized. Thermal recemization (at 293-322 K, in CDCI3) of the chiral chrysene 3,4-oxide (91) has been shown to occur via first-order kinetics, with an activation energy of 25.2 kcal mol" The results are consistent with a reaction mechanism involving an oxepine intermediate (92), as predicted by theory. 

The increasing importance of electron-transfer reactions with increasing aromatic hydrocarbon size is illustrated in the reaction of bromine with various aromatic compounds. With benzene (with a Lewis acid) and with naphthalene, electrophilic substitution occurs, and with anthracene, oxidative addition occurs (6) however, with graphite, only oxidation to the exclusion of carbon-bromine bond formation occurs, even at a stoichiometry of C8Br (II, 12). 

Most of the papers in this section are concerned with photo-oxidation reactions, but a few papers refer to photochemical reactions in polymer matrices. Thus the kinetics of the photo-oxidation of anthracene and naphthacene in solid polystyrene (PS),170 the photoionization of aromatic hydrocarbons dissolved in PMMA and PS,171 the photoreactions of naphthalene in cellulose triacetate,172 the cis-trans isomerization of stilbene residues in the side-chains of polymers,173 intrachain photodimerization in polymers,174 photoisomerization of 1,2-diphenyl-cyclopropane by peptides containing naphthalene in a side-chain,176 and photochemical transformations of poly(vinyl p-azidobenzoate)176 have been reported. 

Methylnaphthalene is commonly used as a feedstock in the production of vitamia K3 (menadione). Methylnaphthalene is oxidized to menadione with chromic or nitric acid, in a similar method to anthracene oxidation. Menadione is used as an intermediate in the production of vitamin Ki.To produce vitamin Ki, menadione is reduced with hydrogen on Pd/activated-carbon catalysts to mena-diol. Esterification of the two hydroxyl groups with acetic anhydride yields mena-diol diacetate, which is converted into the 1-monoacetate with ammonia. Vitamin Ki (phytomenadione) is produced by the reaction of 1-menadiol monoacetate with phytol, using a BF3/ether complex as catalyst, followed by hydrolysis and dehydrogenation. 

Quinones (Table 6.10, item 4) are formed only with difficulty from benzene (CfiH ) itself. However, as shown in Equations 6.77 and 6.78, on oxidation in solution with, for example, ammonium cerium(IV) sulfate [ceric ammonium sulfate, Ce(NHi)4(S04)4], naphthalene (CioHg) and anthracene (C14H10) yield p-quinones and phenanthrene (C14H10), an isomer of the latter (Equation 6.79), yields an o-quinone much more readily. It has been argued that maintaining aromaticity in portions of each of these polynuclear systems aids in making the oxidation reaction much more facile. Similar oxidation patterns are common in naturally occurring quinones. 

Other oxidative dehydrogenation reactions involving 1,2-benzanthracene, anthracene and perylene with strong Lewis acids have been studied, and support Weiss s [14] suggestion that electron transfer occurs in the reaction of aromatic hydrocarbons with Lewis acids and constitutes the first step of organic oxidation reactions. 

Synthesis of Arene Oxides. Reaction of (Me2N)3P with aromatic dialdehydes provides arene oxides such as benz[a]anthracene 5,6-oxide (2a) (eq 5). These compounds, also known as oxiranes, are relatively reactive, undergoing thermal and acid-catalyzed rearrangement to phenols and facile hydrolysis to dihydrodiols. Consequently, their preparation and purification requires mild reagents and condition.s. The importance of this is underlined by successful synthesis of the reactive arene oxide (2b) in 75% yield using appropriate care, despite a previous report of failure of the method. While compound (2b) is a relatively potent mutagen, it is rapidly detoxified by mammalian cells. The principal limitation of the method is the unavailability of the dialdehyde precursors, which are obtained through oxidation of the parent hydrocarbons, e.g. by ozonolysis. 

Examples include luminescence from anthracene crystals subjected to alternating electric current (159), luminescence from electron recombination with the carbazole free radical produced by photolysis of potassium carba2ole in a fro2en glass matrix (160), reactions of free radicals with solvated electrons (155), and reduction of mtheiiium(III)tris(bipyridyl) with the hydrated electron (161). Other examples include the oxidation of aromatic radical anions with such oxidants as chlorine or ben2oyl peroxide (162,163), and the reduction of 9,10-dichloro-9,10-diphenyl-9,10-dihydroanthracene with the 9,10-diphenylanthracene radical anion (162,164). Many other examples of electron-transfer chemiluminescence have been reported (156,165). 

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