Dinitrophenol, reduction

Amino-4-nitropheno1 is produced commercially by the partial reduction of 2,4-dinitrophenol This reduction may be achieved electrolyticaHy using vanadium (159) or chemically with polysulftde, sodium hydrosulftde, or hydrazine and copper (160). Alternatively, 2-acetamidophenol or 2-methylbenzoxazole may be nitrated in sulfuric acid to yield a mixture of 4- and 5-nitro derivatives that are then separated and hydrolyzed with sodium hydroxide (161). 

C6H2(N02)30H (NH SaQs C02+HN03+HCN When mildly reduced, for example with Na sulfide or hydrosulfite or with ferrous sulfate, PA is converted into picramic acid, a very useful intermediate in the dyestuffs industry and a starting material for the preparation of Diazo-dinitrophenol, a primary expl (see Vol 2, B59-L). Stronger reduction may lead to the formation of triamino phenol... 

A strain of Pseudomonas sp. uses 2,6-dinitrophenol as a nitrogen source for growth by first cleaving the nitro groups to free nitrite which, presumably after reduction to NH3, sustains replication of the bacteria. 

Such reductions may result in loss or diminution of the harmful effects as microorganisms convert the broad-spectrum poison 2,4-dinitrophenol to 2-amino-4-and 4-amino-2-nitrophenol, the fungicide pentachloronitrobenzene to penta-chloroaniline, and the insecticide Parathion to aminoparathion. 

Titanium ions can also he used as redox catalysts for the indirect cathodic reduction of nitro compounds (417). The electroreduction is carried out in an H20-H2S04/Ti(S04)2-(Pb/Cu) system at 45 80°C under 5 20Am . Nitrobenzene, dinitrobenzene, nitrotoluene, 2,4-dinitrotoluene, 2-nitro-m-xylene, nitro-phenol, 2,4-dinitrophenol, nitrophenetole, o-nitroanisole, 4-nitrochlorotoluene, ni-trobenzenesulfonic acid, and 4,4 -dinitro-stilbene-2,2 -disulfonic acid can all be reduced by this procedure to the corresponding amino compounds (418) in good yields (Scheme 146) [513-516]. Tin... 

Diazo-4,6-dinitrophenol (DDNP or DINOL) (53) can be prepared from the diazotization of 2-amino-4,6-dinitrophenol (52) (picramic acid) with nitrous acid " the latter is obtained from the selective reduction of picric acid with ammonium sulfide." 2-Diazo-4,6-dinitrophenol (53) is widely used as an initiating charge in detonators and caps. 

The long-known stimulating effect of mono- and polynitro com-pounds on the onset of fermentation in yeast maceration juice has been reinvestigated by Vandendriessche. The induction time is shortened significantly by 2,4- or 2,5-dinitrophenol, while 2,6-dinitro-phenol did not show such an effect. The influence is evident when using as substrates the fermentable hexoses and D-fructose-6-phosphate, but not hexose diphosphate. According to MarkoviCev a stimulation of the oxidation processes can be proved thereby. It is probable that these effects are related to the known phytochemical reduction of nitro compounds (see pp. 98 and 99). 

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... 

Amino-4-nitrophenol has been prepared by the partial reduction of 2,4-dinitrophenol chemically -6 and electrolytically,6 and by the action of sulfuric add on 3-nitroazidobenzene.7... 

Cognate preparation. Reduction of 2,4-dinitrophenol. It is an interesting student exercise to carry out the reduction of 2,4-dinitrophenol under the conditions described above for m-dinitrobenzene. The spectroscopic features of the isolated and purified product, together with the melting point, in comparison with the literature values for the possible isomers, should enable a deduction to be made on the regioselectivity of the reaction. 

Martin [32] found that dinitrophenol undergoes in the body a partial reduction either to 2-amino-4-nitrophenol or to 4-amino-2-nitrophenol Mid 2,4-diamino-phenol. Part of the compound is excreted unchMiged in the wine. 

The first indication of the existence of an energy-linked NADP reduction was brought forward by Krebs (SO) who found that NADPH-dependent dehydrogenase reactions in pigeon heart homogenate were, sensitive to dinitrophenol. This finding formed the basis for the postulate... 

During the 1930s, dinitrophenol was touted as a weight-reduction drug. Dinitrophenol acts to uncouple... 

Dinitrophenols undergo reduction in the presence of NAD PH and nitroreductase and conjugation takes... 

Reduction of the 2-nitro in 2,4,6-trinitrophenol yields picramic acid, 2-amino-4,6-dinitrophenol. It is highly explosive but safe to handle when wet. It was also an important intermediate in dye manufacture. Centralite, a stabilizer in smokeless powders, is made from monoethylaniline. 

The reagent is used in 10% excess for selective reduction of one nitro group of 2,4-dinitrophenol with fair efficiency. Note that the group reduced is that ortho... 

Derivation By reduction of 2,5-dinitrophenol. Hazard May be skin irritant. 

Hemato = hematological hr = hour(s) LD50 = lethal dose, 50% kill LOAEL = lowest-observable-adverse-effect M = male mo = month Musc/skel = musculoskeletal NOAEL = no-observable-adverse-effect NS = not specified Resp = respiratory wk = week(s) x = times NOTE In case reports of humans who took 2,4-dinitrophenol (2,4-DNP) for weight reduction, 2,4-DNP was available both in its free form or as a sodium salt. (The chemical formula for 2,4-DNP is... 

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. 

Eiseman JL, Gehring PJ, Gibson JE. 1974. Kinetics of in vitro reduction of 2,4-dinitrophenol by rat liver homogenates. Toxicol Appl Pharmacol 27 140-144. 

In addition to eliciting a contact hypersensitivity response, benzo[a]pyrene has been shown to suppress this response, to other sensitizers. The effects of dermally applied benzo[a]pyrene (alone or following dermal pretreatment with the prostaglandin synthetase inhibitor, indomethacin) on contact hypersensitivity (cell-mediated immunity), and production of antibodies to dinitrophenol (DNP) (humoral immunity) were studied in male BALB/c mice treated for 6 weeks to 6 months (Andrews et al. 1991a). A group of mice treated with acetone served as controls. Benzo[a]pyrene alone caused a significant reduction (p<0.01) in the contact hypersensitivity response to dinitrofluorobenzene (DNFB) as measured by increases in ear thickness when compared to the vehicle controls. However, indomethacin pretreatment prevented the benzo[a]pyrene-induced contact hypersensitivity response. Benzo[a]pyrene also reduced antibody titres to DNP in treated mice. This suppressive effect on humoral immune function was not restored by pretreatment with indomethacin. These findings led the authors to conclude that the mechanism of... 

Reduction of the aromatic ring — The degradation of phenols containing several nitro groups has revealed an unusual reaction. Although this occurs with the elimination of nitrite — not apparently by any of the pathways illustrated above — terminal metabolites are formed by reduction of the aromatic ring. 4,6-Dinitrohexanoate is produced from 2,4-dinitrophenol (Lenke et al. 1992) and 2,4,6-trinitrocyclohexanone from 2,4,6-trinitrophenol (Lenke and Knackmuss 1992). 

Lenke H. and H.-J. Knackmuss. 1996. Initial hydrogenation and extensive reduction of substituted 2,4-dinitrophenols. Appl. Environ. Microbiol. 62 784—790. 

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