Nitration dinitrotoluene

Substance being nitrated Dinitrotoluene isomers, content % ... 

Further nitration of the 2- and 4- isomers yields 2,4-dinitrotoluene, yellow crystals, m.p. 71 "C. This material is reduced to 2,4-di-aminotoluene and treated with phosgene to give 2,4-diisocyanatotoluene, a precursor of polyurethanes. 

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). 

Organic Reactions. Nitric acid is used extensively ia iadustry to nitrate aHphatic and aromatic compounds (21). In many iastances nitration requires the use of sulfuric acid as a dehydrating agent or catalyst the extent of nitration achieved depends on the concentration of nitric and sulfuric acids used. This is of iadustrial importance ia the manufacture of nitrobenzene and dinitrotoluene, which are iatermediates ia the manufacture of polyurethanes. Trinitrotoluene (TNT) is an explosive. Various isomers of mononitrotoluene are used to make optical brighteners, herbicides (qv), and iasecticides. Such nitrations are generally attributed to the presence of the nitronium ion, NO2, the concentration of which iacreases with acid strength (see Nitration). 

Environmental aspects, as well as the requirement of efficient mixing in the mixed acid process, have led to the development of single-phase nitrations. These can be divided into Hquid- and vapor-phase nitrations. One Hquid-phase technique involves the use of > 98% by weight nitric acid, with temperatures of 20—60°C and atmospheric pressure (21). The molar ratios of nitric acid benzene are 2 1 to 4 1. After the reaction is complete, excess nitric acid is vacuum distilled and recycled. An analogous process is used to simultaneously produce a nitrobenzene and dinitrotoluene mixture (22). A conversion of 100% is obtained without the formation of nitrophenols or nitrocresols. The nitrobenzene and dinitrotoluene are separated by distillation. 

Manufacture and Processing. Mononitrotoluenes are produced by the nitration of toluene in a manner similar to that described for nitrobenzene. The presence of the methyl group on the aromatic ring faciUtates the nitration of toluene, as compared to that of benzene, and increases the ease of oxidation which results in undesirable by-products. Thus the nitration of toluene generally is carried out at lower temperatures than the nitration of benzene to minimize oxidative side reactions. Because toluene nitrates at a faster rate than benzene, the milder conditions also reduce the formation of dinitrotoluenes. Toluene is less soluble than benzene in the acid phase, thus vigorous agitation of the reaction mixture is necessary to maximize the interfacial area of the two phases and the mass transfer of the reactants. The rate of a typical industrial nitration can be modeled in terms of a fast reaction taking place in a zone in the aqueous phase adjacent to the interface where the reaction is diffusion controlled. 

If pure isomers are required, the ortho and meta compounds can be prepared by indirect methods. o-Nitrotoluene can be obtained by treating 2,4-dinitrotoluene with ammonium sulfide followed by diazotization and boiling with ethanol. / -Nitrotoluene can be prepared from -toluidine by acetylation, nitration deacetylation, diazotization, and boiling with ethanol. A fairly pure -nitrotoluene, which has been isolated from the isomeric mixture, can be purified further by repeated crystallization. 

Dinitration of toluene results in the formation of a number of isomeric products, and with a typical sulfuric—nitric acid nitrating mixture the following mixture ofisomers is obtained 75 wt % 2,4-dinitrotoluene [121-14-2] 19 wt % 2,6-dinitrotoluene [606-20-2], 2.5 wt % 3,4-dinitrotoluene [610-39-9], 1 wt %... 

Dinitrotoluene can be prepared by the nitration of -nitrotoluene with yields of ca 96% or it can be obtained from the direct nitration of toluene. 

The y -phenylenediamiaes are easily obtained by dinitrating, followed by catalyticaHy hydrogenating, an aromatic hydrocarbon. Thus, the toluenediamiaes are manufactured by nitrating toluene with a mixture of sulfuric acid, nitric acid, and 23% water at 330°C which first produces a mixture (60 40) of the ortho and para mononitrotoluenes. Further nitration produces the 80 20 mixture of 2,4- and 2,6-dinitrotoluene. Catalytic hydrogenation produces the commercial mixture of diamiaes which, when converted to diisocyanates, are widely used ia the production of polyurethanes (see Amines, aromatic, DIAMINOTOLUENES) (22). 

The nitration step produces two isomers, 2,4-dinitrotoluene and 2,6-dinitrotoluene, the former predorninating. Mixtures of the two isomers are frequendy used, but if single isomers are desired, particulady the 2,4-dinitrotoluene, nitration is stopped at the mono stage and pure i ra-nitrotoluene is obtained by crysta11i2ation. Subsequent nitration of this material yields only 2,4-dinitrotoluene for conversion to the diisocyanate. 

The TDI mixtures are produced by a series of reactions starting from toluene. The first stage is the nitration of the toluene to yield 2-nitrotoluene and 4-nitrotoluene in roughly equal proportions. These can be further nitrated, the 4-isomer yielding only 2,4-dinitrotoluene and 2-nitrotoluene both the 2,4- and the 2,6-dinitro compound Figure 27.1). 

If toluene is dinitrated without separation a mixture of about 80% 2,4-dinitrotoluene and 20% 2,6-dinitrotoluene is obtained. Nitration of separated 2-nitrotoluene will yield a mixture of approximately 65% of the 2,4- and 35% of... 

Trinitrotoluene (TNT) is made by nitration of toluene. Display electrostatic potential maps for toluene, 4-nitrotoluene (the first nitration product) and 2,4-dinitrotoluene (the second nitration product). Are the second and third nitration steps likely to be easier or more difficult than the initial nitration of toluene Explain. 

Toluene (methylbenzene) is similar to benzene as a mononuclear aromatic, but it is more active due to presence of tbe electron-donating metbyl group. However, toluene is much less useful than benzene because it produces more polysubstituted products. Most of tbe toluene extracted for cbemical use is converted to benzene via dealkylation or disproportionation. Tbe rest is used to produce a limited number of petro-cbemicals. Tbe main reactions related to tbe cbemical use of toluene (other than conversion to benzene) are the oxidation of the methyl substituent and the hydrogenation of the phenyl group. Electrophilic substitution is limited to the nitration of toluene for producing mono-nitrotoluene and dinitrotoluenes. These compounds are important synthetic intermediates. 

Dinitrotoluenes are produced hy nitration of toluene with a mixture of concentrated nitric and sulfuric acid at approximately 80°C. The main products are 2,4- and 2,6-dinitrotoluenes ... 

Trinitrotoluene TNT is a well-known explosive obtained hy further nitration of the dinitrotoluenes. 

Kostevich and Sapozhnikov have carried out extensive studies on the nitration of toluene to mononitrotoluene, using nitrating mixts of various compns and determining the compn of mixts leading to dinitrotoluene. Their results are shown in the ternary diagram of Fig 3... 

This reaction cannot be elementary. We can hardly expect three nitric acid molecules to react at all three toluene sites (these are the ortho and para sites meta substitution is not favored) in a glorious, four-body collision. Thus, the fourth-order rate expression 01 = kab is implausible. Instead, the mechanism of the TNT reaction involves at least seven steps (two reactions leading to ortho- or /mra-nitrotoluene, three reactions leading to 2,4- or 2,6-dinitrotoluene, and two reactions leading to 2,4,6-trinitrotoluene). Each step would require only a two-body collision, could be elementary, and could be governed by a second-order rate equation. Chapter 2 shows how the component balance equations can be solved for multiple reactions so that an assumed mechanism can be tested experimentally. For the toluene nitration, even the set of seven series and parallel reactions may not constitute an adequate mechanism since an experimental study found the reaction to be 1.3 order in toluene and 1.2 order in nitric acid for an overall order of 2.5 rather than the expected value of 2. 

Sodium oxide and 2,4-dinitrotoluene, both in the soiid state, were added together to react. There was a very quick reaction that caused the nitrated derivative to combust and cause a fire in the workshop. The violence of this reaction was put down to the absence of any thinner. 

Mixtures with nitrobenzene were formerly used as liquid high explosives, with addition of carbon disulfide to lower the freezing point, but high sensitivity to mechanical stimulus was disadvantageous [1], Dining the recovery of acids from nitration of toluene, mixtures of the oxide with nitrotoluene or dinitrotoluene may... 

Dinitrobenzenes Dinitrotoluenes 1,4-Dioxane Esters Ethylamine Ethers Ethylene Nitric acid Nitric acid Silver perchlorate Nitrates Cellulose, oxidizers Oxidizing materials, boron triiodide Aluminum trichloride, carbon tetrachloride, chlorine, nitrogen oxides, tetrafluo-roethylene... 

The most important raw material is toluene diisocyanate. Nitration of toluene produces o-nitrotoluene (60%) and p-nitrotoluene (40%) which on further nitration gives 2, 4-dinitrotoluene (80%) and 2, 6-dinitrotoluene (20%). Nitration of pure 2-nitrotoluene yields 65 per cent 2,4 and 35 per cent 2, 6-... 

Photolytic. Low et al. (1991) reported that nitro-containing compounds (e.g., 2,4-dinitrophenol) degrade via UV light in the presence of titanium dioxide yielding ammonium, carbonate, and nitrate ions. By analogy, 2,4-dinitrotoluene should degrade forming identical ions. 

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