Fluoranthene oxidation

Hemoglobin is another heme-containing protein, which has been shown to be active towards PAH, oxidation in presence of peroxide [420], This protein was also modified via PEG and methyl esterification to obtain a more hydrophobic protein with altered activity and substrate specificity. The modified protein had four times the catalytic efficiency than that of the unmodified protein for pyrene oxidation. Several PAHs were also oxidized including acenaphthene, anthracene, azulene, benzo(a)pyrene, fluoranthene, fluorene, and phenanthrene however, no reaction was observed with chrysene and biphenyl. Modification of hemoglobin with p-nitrophenol and p-aminophenol has also been reported [425], The modification was reported to enhance the substrate affinity up to 30 times. Additionally, the solvent concentration at which the enzyme showed maximum activity was also higher. Both the effects were attributed to the increase in hydrophobicity of the active site. 

Methods for the synthesis of the biologically active dihydrodiol and diol epoxide metabolites of both carcinogenic and noncarcinogenic polycyclic aromatic hydrocarbons are reviewed. Four general synthetic routes to the trans-dihydrodiol precursors of the bay region anti and syn diol epoxide derivatives have been developed. Syntheses of the oxidized metabolites of the following hydrocarbons via these methods are described benzo(a)pyrene, benz(a)anthracene, benzo-(e)pyrene, dibenz(a,h)anthracene, triphenylene, phen-anthrene, anthracene, chrysene, benzo(c)phenanthrene, dibenzo(a,i)pyrene, dibenzo(a,h)pyrene, 7-methyl-benz(a)anthracene, 7,12-dimethylbenz(a)anthracene, 3-methylcholanthrene, 5-methylchrysene, fluoranthene, benzo(b)fluoranthene, benzo(j)fluoranthene, benzo(k)-fluoranthene, and dibenzo(a,e)fluoranthene. 

Synthesis of 31 by Method I (107,108) and its conversion to the related anti and syn diol epoxide derivatives (32,33) has been reported (108). The isomeric trans-1,lOb-dihydrodiot 37) and the corresponding anti and syn diol epoxide isomers (38,39) have also been prepared (108) (Figure 19). Synthesis of 37 from 2,3-dihydro-fluoranthene (109) could not be accomplished by Prevost oxidation. An alternative route involving conversion of 2,3-dihydrofluoranthene to the i8-tetrahydrodiol (3-J) with OsO followed by dehydration, silylation, and oxidation with peracid gave the Ot-hydroxyketone 35. The trimethylsilyl ether derivative of the latter underwent stereoselective phenylselenylation to yield 36. Reduction of 3 with LiAlH, followed by oxidative elimination of the selenide function afforded 3J. Epoxidation of 37 with t-BuOOH/VO(acac) and de-silylation gave 38, while epoxidation of the acetate of JJ and deacetylation furnished 39. 

FIGURE 10.33 Mechanism of oxidation of fluoranthene by OH in air (adapted from Arey, 1998a). 

FIGURE 10.36 Mechanism of oxidation of fluoranthene by the nitrate radical (adapted from Atkinson and Arey, 1997). 

Repeated cycling through the RUB reduction wave resulted in a decrease in size of the catalytic current. This occurred even when the solution was stirred between cycles. This behavior implies that a blocking or filming of the electrode occurred during the reduction process. Repeated cycling over the oxidation wave removed the film and reactivated the electrode. The electrochemical reduction of 9,10-diphenylanthracene (DPA), 1,3,6,8-tetraphenylpyrene (TPP), anthracene (ANT), fluoranthene FLU) and 2,5-diphenyl-l,3,4-oxadiazole (PPD) in the presence of S Os - all showed similar cathodic waves. 

Fluoranthene derivatives transform into cation radicals upon one-electron oxidation. These species are not stable and quickly undergo a further oxidation. For example, 7,14-dipheny-lacenaphtho[ 1,2-k]fluoranthene gives a ladder polymer according to Scheme 7-3 (Debad Bard 1998.) As a result, an insoluble transparent blue polymer film forms on the electrode. Electrochemical oxidation of the film in acetonitrile initiates a rapid color change from blue... 

When benzenoid organic hydrocarbons such as naphthalene (60), fluoranthene (116), perylene (112) or pyrene (117) are subjected to electrochemical oxidation at a platinum electrode in the presence of supporting electrolytes in solvents such as methylene chloride or acetonitrile, one frequently observes the deposition of crystals on the electrode [310]. When denoting the substrate as A and the supporting electrolyte as MX there are two nucleophilic species competing for the radical cation A", i.e., the neutral molecule A and the closed-shell counteranion X , and it is, indeed, the equilibrium constant of the... 

Oxidation of arenes under nonaqueous conditions often results in polymerization [93], which has been observed for most of the simple arenes, such as benzene [94-97], naphthalene [98], pyrene [99], biphenyl [96], triphenylene [99], fluoranthene [99], and fluor-ene [99-101]. (See Chapter 32 for details.) Polymerization is often accompanied by severe electrode passivation [100]. 

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. 

Numerous aromatic compounds including several bowl-shaped fullerene fragments have been prepared by this method, e.g. cyclopenta[z/]fluoranthene (22, Scheme8, [54d,56a]), cyclopenta[bc]corannulene (23, [55a]) and diace-naphtho[3,2,l,8-cdejg 3, 2, l, 8 -Zmnop]chrysene (24, see Scheme 9, [55b,c]). Of special importance is this approach for the synthesis of cyclopenta-annelated PAHs, e.g. and the three isomeric dicyclopentapyrenes (25-27, Scheme 9, [54e, 56b]). Using these reference samples, several cyclopenta-annelated PAHs could be identified as byproducts formed in the incomplete oxidation of hydrocarbons in fuel rich flames [57]. 

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