Oxidation of fluorene

Resnick SM, DT Gibson (1996) Regio- and stereospecific oxidation of fluorene, dibenzofuran, and dibenzothiophene by naphthalene dioxygenase from Pseudomonas sp. strain NCIB-4. Appl Environ Microbiol 62 4073-4080. 

On the contrary, the oxidation of fluorene in a basic solution is not limited by the deprotonation of hydrocarbon [284]. This is in agreement with the oxidation of fluorene and 9,9-dideuterofluorene at the same rate in DMSO and 1,1-dimethylethanol solution. The stoichiometry of fluorene oxidation is close to unity (except oxidation in HMPA) and the main product of the reaction is fluorenone. The stoichiometry and the initial rate of the reaction depends on the solvent (conditions 300 K, [fluorene] = 0.1 mol L 1, [Me3COK] = 0.2mol L 1,p02 = 97kPa). 

Parent (unsubstituted) PF was first synthesized electrochemically by anodic oxidation of fluorene in 1985 [266] and electrochemical polymerization of various 9-substituted fluorenes was studied in detail later [220,267]. Cyclic voltammogram of fluorene ( r1ed= 1.33 V, Eox = 1.75 V vs. Ag/Ag+ in acetonitrile [267]) with repetitive scanning between 0 and 1.35 V showed the growth of electroactive PF film on the electrode with an onset of the p-doping process at 0.5 V (vs. Ag/Ag+). The unsubstituted PF was an insoluble and infusible material and was only studied as a possible material for modification of electrochemical electrodes. For this reason, it is of little interest for electronic or optical applications, limiting the discussion below to the chemically prepared 9-substituted PFs. 

It is clear from Table 44 that the E2/SN2 ratios observed for reactions of crown ether-separated KOt-Bu ion pairs will greatly depend on the type of substrate and solvent. Di Biase and Gokel (1978) have recently reported many examples of the use of this reagent either as a nucleophile [for example, in its reaction with benzyl chloride and in the reaction with isatoic anhydride (34)] or as a strong base [for example, in the basic oxidation of fluorene to 2-carboxybiphenyl (35)]. 

Oxidation of fluorene (C13H10) with chromic acid gives fluorenone (CnHgO). If the reaction does not go to completion, then a mixture of the starting material and the product is usually obtained. The H NMR spectrum below is from a partially oxidized sample of fluorene so it contains a mixture of fluorene and fluorenone. Determine the relative amounts (mole %) of fluorene and fluorenone in the mixture. 

The present work demonstrates that the oxidation of diphenylmeth-ane in basic solution follows a pattern similar to triphenylmethane and not to fluorene. At high concentrations of good electron acceptors it is possible to realize a situation wherein the rate of oxidation of fluorene is limited by and equal to the rate of ionization. The oxidations of benzhydrol and 9-fluorenol in basic solution are considered the difference in acidity of the methine hydrogens has a pronounced effect on the course of these oxidations. 

The oxidation of fluorene in basic solution is in sharp contrast to diphenylmethane. Figure 1 emphasizes the clean stoichiometry observed in the oxidation of fluorene (one mole of oxygen per mole of fluorene). The over-all reaction for fluorene apparently involves Reactions 1, 2, 6, and 5 (18). 

Table III summarizes some information on the initial rates of oxidation of fluorene in several solvents. In the alcohol-containing solvents the stoichiometry was nearly one molecule of oxygen per mole of fluorene, an observation that excludes 9-fluorenol as an intermediate. In all solvents, including HMPA, interrupted oxidations yielded only fluorenone (or the DMSO-fluorenone adduct) and fluorene. Apparently Reaction 6 or 7 occurs readily in the presence of hydroxylic solvents. In HMPA the high...

The rate of oxidation of fluorene was measured in the presence of various concentrations of nitrobenzene and the better electron acceptor, ra-trifluoromethylnitrobenzene. It was felt that the rate of Reaction 12 should be given by the rate of oxygen absorption (Reaction 13). 

Table IV. Nitrobenzene-Catalyzed Oxidations of Fluorene in tert-Butyl Alcohol Solution at 29.5 °C.

Table V. Oxidation of Fluorene Catalyzed by m-Trifluoromethyl-nitrobenzene in tert-Butyl Alcohol at 29.5 °C.

When pH increased from 2 to 7, the removal rate of fluorene increased however, a subsequent increase in pH from 7 to 12 reduced the removal efficiency back to about the rate at the pH of 2. The increase of pH leads to an increase in the hydroxyl-ion-catalyzed decomposition of ozone into hydroxyl radicals however, the amount of ozone available to undergo direct photolysis and produce hydrogen peroxide will decrease with increasing pH. Eventually more hydroxyl radicals will be produced, which is particularly important at pH 12 (Beltran et al., 1995). The rate of oxidation of fluorene is given by ... 

Rault-Berthelot J, Simonet J (1985) The anodic oxidation of fluorene and some of its derivatives. Conditions for the formation of a new conducting polymer. J Electroanal Chem 182 187-192... 

Hapiot P, Lagrost C, Le Floch F, Raoult E, Rault-Berthelot J (2005) Comparative smdy of the oxidation of fluorene and 9,9-disubstituted fluorenes and their related 2,7 -dimers and trimer. Chem Mater 17 2003-2012... 

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