Dinitrobenzene, isomers

The separation was achieved on an Apiezon L grease SCOT glass capillary column. Complete separation of six dinitrobenzene isomers took 8 min. 

Table 3 presents the experimental enthalpies of formation of polynitrobenzenes and Table 4 presents the calculated additivity values and DSEs for these same compounds. Enthalpy-of-formation values have been determined experimentally for all three dinitrobenzene isomers in the gaseous state. The enthalpy-of-formation difference between the meta and para isomers is indistinguishable from 0. Conventional wisdom suggests that the para isomer should be destabilized relative to the meta because of adjacent positive charges in key ionic or polar resonance structures. Thus it seems that electronic effects due to meta/para dinitro substituent position are small. This small enthalpy-of-formation difference is similar to that for the meta and para dicyano, difluoro and dichloro benzenes, but does not mimic the ca 22 kJ mol 1 difference for the phthalic acids with which the... 

Another early symptom of exposure to 1,3-DNB is cyanosis due to oxygen deprivation because of the presence of methemoglobin in the blood. These changes are also not specific for 1,3-DNB and may be produced by other nitrobenzene compounds and dinitrobenzene isomers. Therefore, cyanosis is not a good biomarker for 1,3-DNB exposure. 

Cossum PA, Rickert DE. 1987. Metabolism and toxicity of dinitrobenzene isomers in erythrocytes from Fischer-344 rats, rhesus monkeys and humans. Toxicol Lett 37 157-163. 

To determine the contents of various isomers in nitration products. Such studies include the work of Giua [23] on systems consisting of DNT and TNT isomers, those of Pascal [24] on systems consisting of dinitro- and trinitronaphthalene isomers, and those of Andrews [25] and of Wyler [26] on systems consisting of dinitrobenzene isomers. The graphs obtained by these authors may be helpful when studying the composition of nitration products. 

Dinitro-3,6-dibromobenzene, monoclinic prisms (from CS2 or glac acet ac), mp 159-60° readily sol in hot abs ale insol in w prepd by nitrating p-dibromobenzene with mixed acid, but a p-dibromo-dinitrobenzene isomer... 

This reaction is used industrially to remove the 1,2- and 1,4-dinitrobenzene isomers from the 1,3 isomer, which does not react, and to eliminate the underired by-product 2,3,4- and 2,4,5-isomers from the explosive TNT. Other aromatic nitro compounds yield sulfamates ... 

BZ was al so partially oxidized by Ag(II) in a small H-cell with stationary platinum electrodes. Compounds identified in anolyte extracts included phenol, hydroquinone, benzoquinone, benzaldehyde, benzoic acid, methyl benzoate, benzonitrile, benzonitrile aldehyde, and 4-nitro butylnitrile. The yellow color of the anolyte was probably due to benzoquinone, which had a relatively high concentration. A compound which was tentatively identified as benzoquinone epoxide ( 11403) was present at the highest concentration and is believed to be a product of the oxidation of benzoquinone. Numerous nitrated aromatics were also detected and include nitrobenzene, dinitrobenzene isomers, nitrophenol isomers, and dinitnophenol isomers. Intermediates are summarized in Table 3 and classified as I. BZ substrate II. nitrated BZs HI. phenols, quinones, and epoxides IV. nitrated phenols V. BZ substituted with aliphatic and aromatic... 

Nitrations are usually carried out at comparatively low temperatures at higher temperatures there may be loss of material because of the oxidising action of the nitric acid. For substances which do not nitrate readily with a mixture of concentrated nitric and sulphuric acids ( mixed acid ), the intensity of the reaction may be increased inler alia by the use of fuming sulphuric acid (containing up to 60 per cent, of sulphur trioxide) or by fuming nitric acid. Thus nitrobenzene is converted by a mixture of fuming nitric acid and concentrated sulphuric acid into about 90 per cent, of wi-dinitrobenzene and small amounts of the o- and p-isomers the latter are eliminated in the process of recrystallisation ... 

The results obtained with methoxypyrazole (247) are attributed to an electronic effect, whereas those obtained with (246) can be explained by taking into account the angular strain in the minor isomer. Reaction of 3(5)-nitropyrazole with l-fluoro-2,4-dinitrobenzene affords exclusively l-(2,4-dinitrophenyl)-3-nitropyrazole (70JHC1237). 

The reaction has been extended to indazole (67BSF2619) from which both isomers have been obtained, and to pyrazolones (68BSF5019). In the latter system N-, O- and C-aryl and even diaryl derivatives have been isolated from the reaction with l-fluoro-2,4-dinitrobenzene. 

Dimethylhydrazine Dimethyl nitrosamine bis (Dimethylthiocarbamoyl) disulphide Dinitrobenzene (all isomers)... 

Treatment of l,2-difluoro-3,5-dinitrobenzene with methoxide leads to a single isomer of fluorodinitroanisole. Obtain the energies of the possible Meisenheimer complexes and predict the structure of the product. Is this outcome consistent with the previously-established directing effect of the nitro group ... 

E8.ll The three possible geometrical isomers of dinitrobenzene are 1,2-, 1,3-, and 1,4-dinitrobenzene. Given the following data at 0.101 MPa pressure... 

Up to three of the hydrogens on a benzene ring can be replaced with a nitro (-NO2) group by reaction of nitric acid in sulfuric acid. When two hydrogens are replaced by nitro in this manner (dinitration), one isomer, the meta- or 1,3-, predominates. When three hydrogens are replaced (trinitration), the predominant isomer is the 1,3,5-isomer mera-dinitrobenzene is made by this method as a starting material for mera-phenylenediamine, one of the components in the manufacture of a heat-resistant nylon sold in the U.S. as Nomex by DuPont. 

A kinetic study of the previously reported substitution of aromatic nitro groups by tervalent phosphorus has established an aromatic 5n2 mechanism. Similarities in values of activation energies, and in relative reactivities of phosphite and phosphonite esters, between this displacement and the Arbusov reaction suggest a related mechanism (31), while the lack of reactivity of p-dinitrobenzene is attributed to the need for intramolecular solvation (32). The exclusive formation of ethyl nitrite, rather than other isomers, is confirmed from the decomposition of triethoxy-(ethyl)phosphonium fluoroborate (33) in the presence of silver nitrite. A mechanism involving quinquevalent phosphorus (34) still seems applicable, particularly in view of the recent mechanistic work on the Arbusov reaction. ... 

The regioselective cross-coupling between anions of bromomalonate esters orbromoacetate esters and m-dinitrobenzene proceeds in the presence of copper fert-butoxide to give the 2-substituted product. Without the copper salt, the 4-substituted isomer is the only product (Eq. 9.35).62... 

As was the case for dinitrobenzene, the meta and para nitroaniline isomers have essentially the same gaseous enthalpy of formation. In the gaseous phase, it is surprising to find that despite the more attractive quinonoid resonance structures92 for the para isomer (58) than for the meta (59) the met a and para nitroaniline have essentially the same gas-phase enthalpy of formation. In the solid and liquid states the intermolecular stabilization lowers the enthalpy of formation of the para isomer relative to the meta. Interestingly, the gas-phase intramolecularly hydrogen-bonded ortho isomer is of comparable stability to its isomers. In contrast, it is considerably less stable than its isomers in the solid state because it can form fewer intermolecular hydrogen bonds. All isomers of nitroaniline are more stable than calculated by additivity. 

The ordering of the two values is hard to rationalize because there are two opposing influences. Because of its shape, p-dinitrobenzene may be expected to pack better than the m-isomer, thereby increasing its relative enthalpy of fusion. However, the latter has a nonzero dipole moment while the former does not. Intermolecular, electrostatic attraction is expected to be stronger for the crystalline meta compound. 

Dichloro-2,4-dinitrobenzene, 2077 2,4,-Dichloronitrobenzene, 2104 3,4-Dichloronitrobenzene, 2105 Dichlorophenol mixed isomers, 2161 f 1,3-Difluorobenzene, 2168 f 1,4-Difluorobenzene, 2169... 

Analysis of the headspace of a group of TNT samples from different sources showed the principal vapor component to be 2,4-dinitrotoluene, with smaller amounts of the other dinitrotoluene isomers, and 1,3-dinitrobenzene [8]. Controlled tests in the olfaction chamber showed that most of the dogs principally responded to 2,4-dinitrotoluene as smelling like TNT and mostly ignored the other compounds [9]. 

The by-products of industrial TNT, including isomers of trinitrotoluene, dinitrotoluene, trinitrobenzene and dinitrobenzene, were investigated using LC/ MS-APCI in the negative-ion mode to build a profile for the characterization of TNT samples from various origins [21], MS/MS-CID was used for further identification of some of the nitroaromatic isomers. 

Exposure. Exposure to 1,3-DNB is currently measured indirectly by determining levels of methemoglobin in the blood (Donovan 1990). However, increased methemoglobin formation is not a specific response to 1,3-DNB exposure and may occur after exposure to other nitrobenzene compounds such as the other two isomers of dinitrobenzene. Determination of methemoglobin levels is widely used and is a reliable detection method. Very few methods are available for direct evaluation of 1,3-DNB levels, and they are not extensively used, probably because of the relatively rapid rate of conversion of 1,3-DNB to its degradation products (Cossum and Rickert 1985). Preliminary data suggested that the formation of adducts of 1,3,5-TNB with tissue DNA and/or with blood proteins may be useful as markers for exposure to 1,3,5-TNB (Reddy et al. 1991). Further research with both 1,3-DNB and 1,3,5-TNB in the area of adduct formation could provide valuable additional information. 

Production volume figures for 1,3-DNB are not easily available because it is produced as a mixture with other nitrobenzene isomers during the manufacturing process. In the United States, DuPont alone reportedly generated 70,000-72,000 pounds of 1,3-DNB annually from production of dinitrobenzene and nitrobenzene (EPA 1991b). The production volumes for 1,3-DNB by other manufacturers are not known. Production data for 1,3,5-TNB by producers in the United States are unknown. 

Blackburn DM, Gray AJ, Lloyd SC, et al. 1988. A comparison of the effects of the three isomers of dinitrobenzene on the testis in the rat. Toxicol AppI Pharmacol 92 54-64. 

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