Dinitrotoluene reduction

As noted above for 2,6-dinitrotoluene, reduction to the amine presumably proceeds in stages, and the intermediate hydroxylamines may undergo chemical rearrangement the metabolism of 4-chlo-ronitrobenzene by a strain of the yeast Rhodosporodinium sp. illustrates this possibility as well as the complete reduction to the amine followed by acetylation (Figure 6.112) (Corbett and Corbett 1981). 

Process Nitration of toluene to dinitrotoluenes Reduction of i dinitrotoluenes i to tolylene diamine Phosgenadon of tolylene diamine... 

Ragaini and colleagues recently studied the influences of acid additives [20-22]. Using the palladium-phenanthroline catalyst system for the carbonylation of nitrobenzene to methyl phenylcarbamate, the addition of anthraniUc acid [20] or phosphorus acids [21, 22] can accelerate the reaction. Anthranilic acid produced higher activity compared with the use of simple benzoic acid. The 4-amino isomer does not show the same increased activity. Later on, they established an improved catalytic system for the carbonylation of nitrobenzene by adding phosphoms acids as an additive, for the first time yielding activities and catalyst fife in the range necessary for industrial applications. By pafladium-phenanthroline complexes and phosphorus acids as promoters, nitrobenzene was carbonylated to methyl phenylcarbamate with unprecedented reaction rates (TOP up to 6,000/h) and catalyst sta-bUity (TON up to 10 ). The best promoter was phosphoric acid, which is very cheap, nontoxic and easily separable from the reaction products. The catalyst system was also applied to the economically very important dinitrotoluenes reduction. 

The nitration of toluene gives a mixture of 2-nitrotoluene (about 60%) and 4-nitrotoluene (40%). If this mixture is nitrated further without separation, the product is a mixture of 2,4-dinitrotoluene (about 80%) and 2,6-dinitrotoluene (20%). If, on the other hand, the mixed mononitrates are separated (by distillation), then further nitration of the 2-nitrotoluene yields a mixture of 2,4-dinitrotoluene (about 65%) and 2,6-dinitro toluene (35%) whilst further nitration of the 4-nitrotoluene gives only 2,4-dinitrotoluene. Reduction of the... 

Formic acid is a good reducing agent in the presence of Pd on carbon as a catalyst. Aromatic nitro compounds are reduced to aniline with formic acid[100]. Selective reduction of one nitro group in 2,4-dinitrotoluene (112) with triethylammonium formate is possible[101]. o-Nitroacetophenone (113) is first reduced to o-aminoacetophenone, then to o-ethylaniline when an excess of formate is used[102]. Ammonium and potassium formate are also used for the reduction of aliphatic and aromatic nitro compounds. Pd on carbon is a good catalyst[103,104]. NaBH4 is also used for the Pd-catalyzed reduction of nitro compounds 105]. However, the ,/)-unsaturated nitroalkene 114 is partially reduced to the oxime 115 with ammonium formate[106]... 

Attempts have been made to develop methods for the production of aromatic isocyanates without the use of phosgene. None of these processes is currently in commercial use. Processes based on the reaction of carbon monoxide with aromatic nitro compounds have been examined extensively (23,27,76). The reductive carbonylation of 2,4-dinitrotoluene [121 -14-2] to toluene 2,4-diaLkylcarbamates is reported to occur in high yield at reaction temperatures of 140—180°C under 6900 kPa (1000 psi) of carbon monoxide. The resultant carbamate product distribution is noted to be a strong function of the alcohol used. Mitsui-Toatsu and Arco have disclosed a two-step reductive carbonylation process based on a cost effective selenium catalyst (22,23). 

Mixtures of HNO, H2SO4, and SO also result in high concentrations of NO/, and toluene can be readily nitrated at —40 to — 10°C as a result (6). At these low temperatures, the formation of the meta-isomer of mononitrotoluene (MNT) is greatiy reduced. Such a reduction is highly desired in the production both of dinitrotoluenes (DNTs) employed to produce intermediates for polyurethane production and of trinitrotoluene (TNT), which is a high explosive. > -MNT results in the production of undesired DNT and TNT isomers (see Nitrobenzene and nitrotoluenes). 

Dinitrotoluenes can be catalytically hydrogenated to toluenediamines under a wide variety of temperatures, pressures, and solvents the catalyst can be supported noble metal, eg, Pd/C or nickel, either supported or Raney type. The reduction requires six moles of hydrogen per mole of DNT and produces four moles of water. 

The complete sequence of reduction products was produced from 2,6-dinitrotoluene by Salmonella typhimurium strain TA 98 (Sayama et al. 1992)—2-nitroso-6-nitrotoluene, 2-hydroxylamino-6-nitrotoluene, and 2-amino-6-nitrotoluene. 

Interactions may take place between metabolites at different levels of reduction. This may plausibly account for the dimerization of partially reduced intermediates to nitro-azoxytoluenes (Bayman and Radkar 1997), and the identification of azoxy componnds as biotransformation products of 2,4-dinitrotoluene by the fungus Mucrosporium sp. (Figure 9.49) (McCormick et al. 1978). 

Noguera DR, DL Freedman (1996) Reduction and acetylation of 2,4-dinitrotoluene by a Pseudomonas aeruginosa strain. Appl Environ Microbiol 62 2257-2263. 

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... 

More complex explosives incorporating amino groups have been prepared from the reaction of polynitroarylene halides with amine nucleophiles. Agrawal and co-workers have synthesized PADNT (107) from the reaction of 4-amino-2,6-dinitrotoluene (46) with picryl chloride (87) in methanol 4-amino-2,6-dinitrotoluene is synthesized from the reduction of... 

The synthesis of TATB (14) from the reaction of 2,3,4,5,6-pentanitroaniline (31) with ammonia has been reported. " In one route, 2,3,4,5,6-pentanitroaniline (31) is synthesized from the nitration of 3,5-dinitroaniline (30) " the latter is obtained from the selective reduction of TNB ° or via a Schmidt reaction with 3,5-dinitrobenzoic acid. Another route to 2,3,4,5,6-pentanitroaniline (31) involves the selective reduction of TNT (1) with hydrogen sulfide in ammonia followed by nitration of the resulting 4-amino-2,6-dinitrotoluene (46), during which the methyl group is lost by oxidation-decarboxylation. 

Two other derivatives of toluene are the important explosive trinitrotoluene (TNT) and the polyurethane monomer toluene diisocyanate (TDI). TNT requires complete nitration of toluene. TDI is derived from a mixture of dinitrotoluenes (usually 80% o,p and 20% o,o) by reduction to the diamine and reaction with phosgene to the diisocyanate. TDI is made into flexible foam polyurethanes for cushioning in furniture (35%), transportation (25%), carpet underlay (20%), and bedding (10%). A small amount is used in polyurethane coatings, rigid foams, and elastomers. 

Toluene diisocyanate (TDI) is made from the reaction of 2,4-toluenediamine and phosgene. The diamine is made by reduction of dinitrotoluene, which in turn is manufactured by nitration of toluene. See Chapter 11, Section 7. 

These are products extracted out of soil contaminated with TNT, RDX, and TETRYL (Trimtrophcnyl-M-mcthyInitramine). For TNT a decomposition product that had a longer half-life in the soil was 4-amino-dinitrotoluene, so in doing area reduction one should include this product. 

Another example of bubble columns is hydrogenation of olefins and other organics, such as reduction of dinitrotoluene... 

A similar example is 2,6 dinitrotoluene where reduction in rats of a nitro group to a hydroxylamine occurs, which yields a liver carcinogen (see chap. 5). 

Riefler, R. G., and B. F. Smets, Enzymatic reduction of 2,4,6-dinitrotoluene and related nitroarenes Kinetics linked to one-electron redox potentials , Environ. Sci. Technol, 34, 3900-3906 (2000). 

The use of iron and a little hydrochloric acid (or alternatively of iron and acetic acid) is to be preferred when the use of the more strongly acidic medium leads to the formation of undesirable by-products nuclear chlorination, for example, often results when tin or zinc is used in association with concentrated hydrochloric acid. A suitable experimental procedure for the reduction of 2,4-dinitrotoluene to 2,4-diaminotoluene has been described.23... 

Toluene diisocyanate is derived from a mixture of dinitrotoluenes (usually 65 to 85% o./9-dinitrotoluene and 35 to 15% o,o-dinitrotoluene) followed by reduction to the diamine and reaction with phosgene to the diisocyanate. 

Groundwater estimated t,/2 = 1.0 d in Rhine River in case of a first order reduction process (Zoeteman et al. 1980) t/2 = 48- 9456 h, based on estimated unacclimated aqueous anaerobic biodegradation half-life for 2,4-dinitrotoluene and estimated unacclimated aqueous aerobic biodegradation half-life (Howard et al. 1991). Sediment ... 

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