Toluene nitric acid reaction

The operation of the nitronium ion in these media was later proved conclusively. "- The rates of nitration of 2-phenylethanesulphonate anion ([Aromatic] < c. 0-5 mol l i), toluene-(U-sulphonate anion, p-nitrophenol, A(-methyl-2,4-dinitroaniline and A(-methyl-iV,2,4-trinitro-aniline in aqueous solutions of nitric acid depend on the first power of the concentration of the aromatic. The dependence on acidity of the rate of 0-exchange between nitric acid and water was measured, " and formal first-order rate constants for oxygen exchange were defined by dividing the rates of exchange by the concentration of water. Comparison of these constants with the corresponding results for the reactions of the aromatic compounds yielded the scale of relative reactivities sho-wn in table 2.1. 

Ingold and his co-workers used the competitive method in their experiments, in which nitration was brought about in acetic anhydride. Typically, the reaction solutions in these experiments contained o-8-I 4 mol of nitric acid, and the reaction time, depending on the reactivities of the compounds and the temperature, was 0-5-10 h. Results were obtained for the reactivities of toluene, > ethyl benzoate, the halogenobenzenes, ethyl phenyl acetate and benzyl chloride. Some of these and some later results are summarized in table 5.2. Results for the halogenobenzenes and nitrobiphenyls are discussed later ( 9.1.4, lo.i), and those for a series of benzylic compounds in 5,3.4. 

Expts. 16, //. Pure nitric acid was used. In expt. 16 the reaction was of the first order in the concentration of the aromatic, and of half-life 1-1-5 minutes (similar to that of toluene under the same conditions). In expt. 17 the sodium nitrate slowed the reaction (half-life c. 60 min). About 2 % of an acetoxylated product was formed (table 5-4). 

Nitrations can be performed in homogeneous media, using tetramethylene sulfone or nitromethane (nitroethane) as solvent. A large variety of aromatic compounds have been nitrated with nitronium salts in excellent yields in nonaqueous media. Sensitive compounds, otherwise easily hydroly2ed or oxidized by nitric acid, can be nitrated without secondary effects. Nitration of aromatic compounds is considered an irreversible reaction. However, the reversibihty of the reaction has been demonstrated in some cases, eg, 9-nitroanthracene, as well as pentamethylnitrobenzene transnitrate benzene, toluene, and mesitylene in the presence of superacids (158) (see Nitration). 

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. 

Reactant amount 40 g, fumed nitric acid (> 95%), nitric acid/toluene (n/n)=l. 4, reaction temperature 65 C, reaction time 3 h. 

Theory Selenium is very toxic and its contamination is usually controlled by an absorptiometric method after destruction of the organic compound with fuming nitric acid. The latter converts selenium (Se) as selenous acid (H2Se03), which on subsequent treatment with 3,3 -diaminobenzidinc under controlled experimental parameters, results into the formation of a highly coloured compound known as 3,4-diaminophenylpiazselenol. The latter is consequently extracted with toluene after making the aqueous solution alkaline, and the colour compared with a standard prepared likewise from a known amount of selenium. The various reactions involved may be expressed as follows ... 

It is clear that there are few restrictions to the possible reactions that can be studied. Of particular interest is an article demonstrating that the nature of the ionic liquid can dramatically influence the outcome of a reaction. In a study of the reactions between toluene and nitric acid, three completely different products were obtained by using three different ionic liquids (see Figure 5.8). Despite the thousands of articles demonstrating the synthetic utility of ionic liquids, however, there are only, as yet, a few on mechanism, the most notable being from Welton s... 

Figure 5.8 The reactions between toluene and nitric acid in (a) a halide-based ionic liquid, (b) a triflate-based ionic liquid, and (c) a mesylate-based ionic liquid.

The nitro compounds are organic compounds linked with the grouping -NO2. Usually the -NO2 comes from nitric acid, HNO3, as in the reaction of nitric acid and toluene to malce 2,4,6 tri-nicro-toluene, which is TNT The numbers are a code indicating where the three nitro groups are attached in relation to the methyl group in toluene. 

Both nitric acid and nitrogen dioxide, in the liquid and vapour phase, have been used for the nitration of the alkyl side chains of various alkyl-substituted aromatics without affecting the aromatic nucleus.Thus, treatment of ethylbenzene with nitric acid of 12.5 % concentration in a sealed tube at 105-108 °C is reported to generate a 44 % yield of phenylnitroethane. The nitration of toluene with nitrogen dioxide at a temperature between 20-95 °C yields a mixture of phenylnitromethane and phenyldinitromethane with the proportion of the latter increasing with reaction temperature. ... 

The nitration of l,3,5-trichloro-2-nitrobenzene (8) to l,3,5-trichloro-2,4-dinitrobenzene (9) with dinitrogen pentoxide in absolute nitric acid goes to completion in only 2-4 minutes at 32-35 °C. Further nitration of (9) would yield l,3,5-trichloro-2,4,6-trinitrobenzene (10) which undergoes ammonolysis on treatment with ammonia in toluene to give the thermally stable explosive 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) (11). The same sequence of reactions with l,3-dichloro-2-nitrobenzene provides a route to l,3-diamino-2,4,6-trinitrobenzene (DATE). Such reactions are clean and occur in essentially quantitative yield. 

Conversion of toluenes to the benzoic acid is also accomplished by anodic oxidation in acetic acid containing some nitric acid. It is not clear if this reaction involves the aromatic radical-cation or if the oxidising agents are nitrogen oxide radicals generated by electron transfer from nitrate ions [66, 67]. Oxidation of 4-fluorotoluene at a lead dioxide anode in dilute sulphuric acid gives 4-fluorobenzoic acid in a reaction which involves loss of a proton from the aromatic radical-cation and them in further oxidation of the benzyl radical formed [68]. 

The next problem with this reaction is that the mononitro compound can add successive nitro groups to produce the di- and trinitro toluenes in the reactions. Fortunately, the rate coefficients for adding the second and especially the third nitro groups are much smaller than for adding the first so mononitrotoluene can be made with good efficiency by simply heating toluene in nitric acid (Figure 3-19). 

Earle et al reported the first proof of the paradigm that the outcome of a chemical reaction can be radically altered by the choice of the ionic liquid as the solvent for the catalyst. The reactants were toluene and nitric acid in HCl for the following three ILs (1) [bmim][OTf, (2) [bmim][X], and (3) [bmim][OMs] where OTf is the trifluoromethanesulfonate anion, X = halide, and OMs = methanesulfonate salt. The reactions observed are described in Scheme 1. 

TNT is the abbreviation of the aromatic nitrated aromatic compound 2,4,6-trinitrotoluene. It is a pale-yellow crystalline solid that was first synthesized in 1863 by the German chemist Joseph Wilbrand (1811—1894), but it was not immediately used as an explosive. TNT is made by nitrating toluene using nitric acid, sulfuric acid, and oleum (a mixture of sulfuric acid and S03). Nitration of toluene occurs in stages, with the nitro units added sequentially in a stepwise process as the reaction proceeds. The last nitro unit is accomplished by using oleum (SO, dissolved in sulfuric acid). After nitration, unused acids are recycled, and the product is washed with sodium sulfite and water to remove impurities. 

Place 18 g. (12 ml.) of fuming nitric acid, sp. gr. 1 5, and 30 g. (16 5 ml.) of concentrated sulphuric acid and a few fragments of broken glass in a 250 or 500 ml. round-bottomed flask. Add gradually, in small portions, 14 g. of p-nitro toluene do not allow the temperature to rise above 50° and cool the flask, if necessary, by immersion in cold water. Place a small funnel in the mouth of the flask and heat on a water bath at 90-95° for 30 minutes. Allow to cool almost to the laboratory temperature and pour the reaction mixture slowly into about 500 ml. of ice water containing a few small pieces of ice. Filter the crude dinitrotoluene through a Buchner funnel at the pump, wash it thoroughly with cold water, and drain as completely as possible. Recrystallise from the minimum volume of hot methyl alcohol (flask, reflux condenser, and water bath experimental details as in Section IV,12). The yield of pure 2 4-dinitrotoluene, m.p. 71°, is 12-5 g. 

TABLE 1 Formation of MNT (mononitrotoluenes), DNT (dinitrotoluenes) and MDPM (methyldiphenylmethanes) from toluene by using nitric acid in conjunction with a commercial acidic clay of the montmorillonite type (toluene 1.45 mole 100 % HN03 21 mmole clay 90 g. Reaction time 3.5 hr). 

Accordingly, the role of water might be explained in the following way in the absence of water, protonation of toluene can induce arylation, whereas, in the presence of water, the acidity of the clay is just sufficient to protonate nitric acid and to favour the formation of an ipsosubstituted Wheland intermediate. The most reasonable reaction sequence compatible with our observations is depicted in scheme 1 and eq. 4. 

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