Para-Nitrotoluene

Metabolism and genetic toxicity have been reported to differ with the isomer of nitro-toluene. p-Nitrotoluene was not mutagenic in bacterial assays, but it did increase sister chromatid exchange frequencies and chromosomal aberrations in vitro-, in vivo it did not increase the frequency of micronuclei in bone marrow of treated rodents. Similar findings were reported for the ortho isomer, except that it did not induce chromosomal aberrations in vitro. Only the ortho isomer induces DNA excision repair in the in vivo-in vitro hepatocyte unscheduled DNA synthesis assay. Furthermore, ort/jo-nitrotoluene binds to hepatic DNA to a much greater extent than meta- or para-nitrotoluene, and investigators suggest that it may act similarly to the rodent hepatocarcino-gen 2,6-dinitrotoluene. ... 

In the [Ru(CO)3(dppe)] catalysed carbonylation of para-nitrotoluene (Eq. (6)) HP IR spectroscopy indicated conversion of the Ru(0) complex into an oxidised species with v(CO) bands at higher frequency [41]. A mechanism involving single-electron-transfer from the nitroaromatic to the Ru complex was proposed. 

Toluene, like benzene, undergoes electrophilic substitutions, where the substitutions take place in ortho and para positions. As the —CH3 group is an activating group, the reaction rate is much faster than usually observed with benzene. For example, the nitration of toluene produces ortho-nitro-toluene (61%) and para-nitrotoluene (39%). 

Aromatic nitrations performed in the presence of KIO montmori11onite lead to increased para selectivity. With toluene as test molecule, the proportion of para-nitrotoluene reaches 79% when using clay-supported copper(II) nitrate ("claycop") in the presence of acetic anhydride under high dilution conditions in CC1 (ref. 

Up to a // value of — 10, all indicators are primary amines and are therefore suitable for the measurement of the Hammett H() function. For stronger acids, new indicators such as nitro compounds have to be used. Although the acidity function scale based upon nitro compounds as indicators may not be a satisfactory extension of the aniline indicator scale, Gillespie and Peel18 have shown that the most basic nitro compound indicator, para-nitrotoluene overlaps in a satisfactory manner with the weakest indicator in the aniline series, 2,4,6-trinitroaniline. Thus, the acidity measurements using the nitro compounds may be considered to give the best semiquantitative picture of the acidity of the various superacid systems. 

Using the previous information in this section, predicting the position that a second substituent group will take on a benzene ring is easy. For example, the nitration of methyl benzene (toluene) will produce ortho and para nitrotoluene as the main product because the methyl group is an ortho-para director. 

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 0b = kab3 is implausible. Instead, the mechanism of the TNT reaction involves at least seven steps (two reactions leading to ortho- or para-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 study4 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. 

By comparing the above summaries, it is seen that the ortho compound of the earlier chemists is identical with the present meta nitrotoluene, and vice versa. That the early view was incorrect may be further proved by investigating the properies of the meta compounds. In all reactions the meta compounds react differently from the ortho and para compounds. For instance, in the nitration of toluene, the ortho and para nitrotoluenes are formed in large amounts, and the meta in small amounts. Further, when the mono-nitrotoluenes are nitrated to dinitrotoluene, the ortho and para mononitrotoluenes are very easily nitrated further, and the meta difficultly so. In other words, the ortho and para compounds form one part of the class, while the meta stands alone as the other part. With the early nomenclature, the meta and para would be placed together, while the ortho would stand alone. If, now, this view of the matter is accepted. Von Richter s statement becomes entirely correct. 

Meta nitrotoluene crystallizes in monoclioic prisms, and para nitrotoluene crystals belong to the trunetric system. 

A possibly better method of separating the isomeric mononitrotoluenes is. one used by the firm of Meister, Lucius Bruning. This consists in cooling the mixed nitrotoluenes to —4 to —10 °, and removing the liquid portion after about one-half the mixture has ci ystallized. The separation may be effected by a centrifuge. The liquid obtained by one crystallization is practically pure ortho nitrotoluene. The resulting mixture of meta and para nitrotoluenes may be separated by steam distillation. The para is very volatile with steam, while the meta is but slightly so. 

A considerable amount of para nitrotoluene may be separated from the above residue, and easily enough so that further methods of preparation would be superfluous. A very small amount of the meta nitrotoluene is present, also, but this amount is too small to be of... 

I he mononitrotoluenes form addition products with le ih.Tgariic salts. This property differs from the rjr ifri M hi. s. niJeh form their addition products i ii-Mi V ti. or. iio tvniiioiuiils. Walker and Spencer . h ,>e pfs luce i an aluminium chloride compound of ij..riOii triitolii ne. and Mascarelli (7) isolated an n t oi para nitrotoluene and mercuric... 

Triplet exclplexes formed from the triplet excited states of zinc and magnesium etioporphyrin I (ZnEtio I and MgEtlo I) and zinc octaethylporphyrin (ZnOEP) with acceptors such as nitro-aromatics and organochloro compounds were directly observed by conventional flash spectroscopy (250-252). The nature and decay properties of the exclplexes are sensitive to quencher concentration and medium composition. For example, as the concentration of para-nitrotoluene (PNT) was Increased in benzene solutions of ZnEtioI, the lifetime of the transient observed after flash excitation of the metal complex proportionately Increased up to a maximum and then decreased (250). The first effect was attributed to the formation of long-lived exclplexes involving two PNT molecules as shown in the scheme below, where D = metallopor-phyrin and A = PNT ... 

The vapor phase studies also showed that the size of the pores has an important effect on the regioselectivity of the reaction. Fig. 2 illustrates the effect of pore size on product selectivity. The highest selectivity for para-nitrotoluene was observed over H-ZSM5 followed by Mordenite, L, and MCM. The kinetic diameters of the o-, m-, and p- isomers are 6.7, 6.7, and 5.25 A respectively. Experimental results shown in Fig. 2 verify that catalysts with channel diameters of less than 7 A preferentially form the para isomer. Based on these geometric arguments alone, the small amount of ortho isomer observed with the H-ZSM5 catalyst could be generated on acid sites located on the outer surface (2). 

A similar shape selective effect was observed in the liquid phase. Those catalysts with the smaller pore and channel openings were more selective for para-nitrotoluene. However, in the liquid phase, no induction period was observed. Rather, all catalysts exhibited significant deactivation throughout time on stream and after 5 hrs. little of the original activity remained. As shown in Fig. 3, the para selectivity was found to decrease with time on stream. This would indicate that deactivation occurs within the pore channels effectively reducing the preferential capacity of the catalyst to generate the para isomer. The decrease in para selectivity was not evident on Beta zeolite, which has larger pores and may allow for a more uniform production of... 

High selectivities to para-nitrotoluene can be obtained using acid zeolites at mild reaction conditions. However, the catalysts rapidly deactivate by two main mechanisms. At the low temperature range, the dominant form of deactivation is the plugging of the pores by the aromatic molecules. As the temperature increases, the adsorption of hydrocarbon species and pore plugging decreases, but the catalysts deactivate by coke formation. 

This reaction cannot be elementary. We can hardly expect three nitric acid molecules to react at all three toluene sites (these are primarily the ortho and para sites meta substitution is not favored) in a glorious, four-body collision. Thus the fourth-order rate expression (R = kab is implausible. Instead, the mechanism of the TNT reaction involves at least seven steps (two reactions leading to ortho- or para-nitrotoluene, three reactions leading to 2,4- or 2,6-dinitrotoluene, and two reactions leading to... 

SYNONYMS l-methyl-4-nitrobenzene, 4-methylnitrobenzene, p-methylnitrobenzene, 4-nitrotoluene, para-nitrotoluene. 

Low Substrate and High Positional Selectivity. Nitrations with nitronium tetrafluoroborate in nitromethane and nitronium hexa-fluorophosphate in nitromethane solution, respectively, show low substrate selectivities (generally expressed by the k /kg rate ratios) but at the same time the nitrations maintained high positional selectivity. Typical isomer distributions in the nitration of toluene are 6 J% ortho, k% meta, and 29% para nitrotoluene. The data summarized in Table XIV show the relative reactivities of a number of alkylbenzenes over those of benzene, together with the isomer distributions of the mononitro products. 

Synonyms/Trade Names p-MethyInitrobenzene, 4-Methylnitrobenzene, para-Nitrotoluene, 4-Nitrotoluene... 

There is generally no significant change of positional selectivity io nitration of aromatics with A -nitropyridinium ion. In the case of toluene, the isomer distribution is 62-64% ortho- 2-4% meta- 33-36% para-nitrotoluene,... 

Scheme 6.95. A possible pathway for the alkylation of nitrobenzene by the methylsulfinylmethide anion [CH3(SO)CH2 j. Although only para- alkylation to produce 4-nitromethylbenzene (para-nitrotoluene) is shown, ortho- alkylation also occurs. A similar pathway can be written for the latter.

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