2.4- dinitrophenol transformation

Knowledge of the enzymes used by microorganisms in the transformation of nitroaromatic compounds is limited. Blasco Castillo (1993) characterized an inducible nitrophenol reductase from Rhodobacter capsulatus that catalyzed the reduction of 2,4-dinitrophenol (DNP) to 2-amino-4-nitrophenol. This enzyme was a dimer that contained flavin mononucleotide and possibly nonheme iron as... 

Wallnoefer PR, Ziegler W, Engelhart J, et al. 1978. Transformation of dinitrophenol herbicide by Azobacter sp. Chemosphere 12 967-972. 

Absence of nitro derivatives was also observed upon irradiation of nitro-phenols and nitrate. Also in this case, the electron-withdrawing character of the nitro group can account for the inhibition of nitration [109]. The difficulty to nitrate nitrophenols to dinitrophenols is widely recognised [125] and also constitutes a problem in environmental chemistry, since field data seem, in contrast, to indicate that the nitration of 2-nitrophenol to 2,4-dinitrophenol in the atmospheric aqueous phase (e.g. cloud water) is an important process [126]. In fact, aqueous-phase nitration might be a relevant sink for 2-nitrophenol and possibly the main source of the dinitro compound, which is a powerful phytotoxic agent [127,128]. In the presence of nitrate under irradiation the main transformation intermediates of nitrophenols are the hydroxyl derivatives, while other compounds may derive from the direct photolysis of the substrates (catechol and 2-nitrosophenol from 2-nitrophenol hydroquinone, benzoquinone, hydroxybenzoquinone and 4-nitrosophenol from 4-nitrophenol) [109]. 

Gold and Rochester (S4] and Johnson and Rees [55] described a transformation of 13iS-trinitrobenzene into 3,S dinitrophenol under photochemical action of OH [compare with reaction (11) in Vol. I, p. 251 ]. 

Dinitrophenols are released to the environment primarily during their manufacture and use, and from waste disposal sites that contain dinitrophenols (Games and Hites 1977 HSDB 1994 McLuckey et al. 1985 Patil and Shinde 1988). Dinitrophenols also form in the atmosphere from the reaction of benzene with NO in ambient air (Nojima et al. 1983). Significant removal of dinitrophenols from the atmosphere due to photochemical or other chemical reactions is not likely. Dry and wet deposition of particulate dinitrophenols are the two significant removal processes in the air (Alber et al. 1989 Capel et al. 1991 Levsen et al. 1990). Neither photochemical nor other chemical processes have been identified that are significant for the transformation/degradation of dinitrophenols in natural waters (Callahan et al. 1979 Lipczynska-Kochany 1992 Tratnyek and Hoigne 1991 Tratnyek et al. 

No study was located that reported the abiotic degradation/transformation of dinitrophenols in soil. It has been speculated that 2,4-DNP in soil may be reduced to 2-amino-4-nitrophenol by sunlight in the presence of a reductant, such as ferrous ions and a sensitizer, such as chlorophyll (Kaufman 1976 Overcash et al. 1982 Shea et al. 1983). Considering, however, that sunlight would not penetrate below the surface layer of soil, photolysis would not be significant at subsurface levels. 

Scheme 53 illustrates the path (a). In one of the pioneer pubhcations on such type of transformations, Severin et al. [90] described the interaction of disodium salt 115 (adduct of 2,4-dinitrophenol and acetone) with methylamine and formaldehyde in the presence of acetic acid. As a result, bicyclic derivative 116a of 3-azabicyclo [3.3.1]nonane was isolated in 62% yield (Scheme 53). Analogous product 116b was obtained in 48% yield, when cyclohexanone was used as C-nucleophile [90].

Another research group has applied this approach to the synthesis of polyfunctional 3-azabicyclo[3.3.1]nonanes from 2,4-dinitrophenol [91]. It has been reported that various alkyl amines and amino acids can be successfully used in these transformations. 

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