Nitrobenzene Compounds Research Articles

Detection of Explosives and Explosives-Related Compounds by Single Photon Laser Ionization Time-of-Flight Mass Spectrometry

The application of single photon ionization in combination with mass-selective detection by time-of-flight mass spectrometry is described for the rapid detection of the nitro-containing explosives and explosives-related compounds nitrobenzene, 1,3-dinitrobenzene, o-nitrotoluene, 2,4-dinitrotoluene, and 2,4,6-trinitrotoluene, as well as the peroxide-based explosive triacetone triperoxide in the gas phase. The technique is demonstrated to be a plausible approach for laser-based rapid detection of explosives. The limits of detection for nitrobenzene and 2,4-dinitrotoluene using SPI were also measured and determined to be 17-24 (S/N approximately 2:1) and approximately 40 ppb (S/N approximately 2:1), respectively.

Acute Lethal Toxicity of Environmental Pollutants to Aquatic Organisms

The acute lethal toxicity of environment pollutants including chlorophenol, haloalkane, quinone, and substituted nitrobenzene (i.e., nitrophenol, nitrobenzene, nitrotoluene, and aniline) compounds to aquatic organisms was determined. Determination of toxicity of chemicals was performed with chlorella, daphnia, carp, and tilapia. The toxicity of chlorophenols had no relation to the number of chlorine atoms on the benzene ring, but monochlorophenol had lower activity than more chlorine-substituted compounds. The tolerance levels of daphnia and carp to haloalkanes was found to be higher than that of chlorella; toxicity to chlorella was several hundred times higher than to daphnia. The toxicity of naphthoquinone compounds to chlorella and carp was higher than that of anthraquinone. A compound with a monochloride substitution on anthraquinone ring was less toxic to carp than those substituted with amine, hydroxyl, and dichlorine groups. Nitrobenzene compounds with an additional substitution group on the p position were extremely toxic to daphnia and carp.

Nitrobenzene Compounds Inhibit Expression of VCAM-1

A series of nitrobenzene compounds has been discovered as potent inhibitors of VCAM-1 expression and, therefore, potential drug candidates for autoimmune and allergic inflammatory diseases. Structure–activity relationship (SAR) studies showed that a nitro group and two other electron-withdrawing groups are essential for these compounds to be potent inhibitors of VCAM-1 expression.

Biodegradation of nitrobenzene by its simultaneous reduction into aniline and mineralization of the aniline formed

By mixing through a three-reactor system a nitroreducing consortium and an aniline-degrading Comamonas acidovorans, a mixed population was formed which was able to mineralize the nitroaromatic compound nitrobenzene via aniline, its corresponding aminoaromatic compound. The behavior of the mixed population was characterized in batch culture. In the first step, nitrobenzene was reduced to aniline by the reductive consortium and, in the second, oxidative step, aniline was mineralized via catechol and meta cleavage. Even though these two steps may seem incompatible in terms of required redox conditions, they were made to coexist in a single, simple reactor. However, when aeration was optimum for growth, only 16% of the 0.5 mM nitrobenzene introduced was mineralized. Decreasing the aeration led to an increase in the amount of nitrobenzene reduced and decreased its volatilized fraction. A decrease in aeration did not slow down aniline mineralization, although the latter is catalyzed by dioxygenases. This mixed population is thus able to remediate nitrobenzene and also aniline, which is often found with the former in the environment. Using C. acidovorans, which also degrades methylanilines, or other aminoaromatic-compound-degrading organisms, this strategy should be applicable to mineralizing more complex nitroaromatic compounds, like nitrotoluenes or dinitrotoluenes.

Effects of 1-Chloro-2,4,6-Trinitrobenzene on 5-Lipoxygenase Activity and Cellular Leukotriene Synthesis

5-Lipoxygenase (EC 1.13.11.34) is the key enzyme in the regulation of leukotriene synthesis. Here, the effects of various substituted nitrobenzene compounds on 5-lipoxygenase activity and the formation of leukotriene B 4 (LTB 4) were studied in polymorphonuclear leukocytes (PMNL), B lymphocytes, and human whole blood. 1-Chloro-2,4,6-trinitrobenzene (TNCB) was found to inhibit calcium ionophore A23187-induced leukotriene synthesis in PMNL in a biphasic manner. Thus, 1.0 μM TNCB caused 50% inhibition of LTB 4 formation, but only 16% inhibition was found at 10 times higher concentration. In contrast, this higher concentration of TNCB activated the synthesis of LTB 4 when PMNL were stimulated with arachidonic acid alone, demonstrating that TNCB can exert both stimulatory and inhibitory effects on leukotriene synthesis depending on the experimental conditions. The inhibitory effect of 1.0 μM TNCB on ionophore A23187-induced leukotriene synthesis could be circumvented by addition of exogenous arachidonic acid. At high concentrations of TNCB (25–100 μM), the drug blocked ionophore A23187-induced leukotriene synthesis. TNCB also inhibited LTB 4 formation in B lymphocytes, as well as in human whole blood. The activity of recombinant 5-lipoxygenase was inhibited by TNCB, and reduced glutathione or β-mercaptoethanol counteracted this inhibition. This suggests that TNCB might inhibit 5-lipoxygenase by alkylating thiol groups. TNCB possessed a high specificity for 5-lipoxygenase with only modest inhibitory effects on 12-lipoxygenase (EC 1.13.11.31), 15-lipoxygenase (EC 1.13.11.12), and phospholipase A 2 (EC 3.1.1.4) activities. Taken together, these results show that TNCB can both specifically inhibit and stimulate leukotriene formation and might be useful in further studies on the regulation of 5-lipoxygenase.

Tetralin, indan and nitrobenzene compound structure-musk odor relationship using neural networks

Summary Structure-musk odor relationships were established by means of a neural network (NN) on a sample of 105 molecules comprising nitrobenzene compounds, carbonyl tetralins and carbonyl indans. Each molecule was described by eight variables (six steric hindrance descriptors and two electronegativity descriptors, coding six substituents on a common underlying skeleton (benzene ring with a tertiobutyl or pseudo-tertiobutyl group in the meta position relative to a nitro or carbonyl group)). Odor was coded by a binary variable. Seventeen molecules could be coded by two different descriptions, and so the back-propagation NN was trained on 122 descriptions. The NN gave a better classification (98.1%) than that obtained by discriminant analysis (65.7%). To test the reliability of the NN approach, training was made on 11 training subsets of 111 or 110 descriptions with a correct classification rate of 96.4 to 98.6%. For the 11 corresponding test subsets of 11 or 12 descriptions a correct prediction rate of 80% was obtained for the 105 molecules. The contribution of each descriptor was evaluated. The results show the possibility of establishing structure-musk odor relationships for molecules with different structures and confirm the previously mentioned effect of steric hindrance in the ortho position of the functional groups interacting with the receptor by hydrogen bonding.

Determination of the semi-volatile compounds nitrobenzene, isophorone, 2,4-dinitrotoluene and 2,6-dinitrotoluene in water using solid-phase microextraction with a polydimethylsiloxane- coated fibre

Aqueous samples of the semi-volatile compounds nitrobenzene, isophorone, 2,4-dinitrotoluene and 2,6-dinitrotoluene listed in the US Environmental Protection Agency (EPA) Method 609, were analysed by solid-phase microextraction (SPME) with a polydimethylsiloxane-coated fibre. SPME is a technique to extract organics from an aqueous matrix into a stationary phase immobilized on a fused-silica fibre. The analytes are thermally desorbed directly into the injector of a gas chromatograph. The sensitivity of this method decreased with increasing concentration of methanol and absorption temperature and increased with increasing concentration of Na 2SO 4. Samples of lake water were analysed using calibration graphs based on deionized water. The relative standard deviations of these analytes were 1–2% for analytes in deionized water and 2–4% for analytes in lake water. The detection limits were 9 ng/ml for nitrobenzene and 15 ng/ml for the other three analytes.

ChemInform Abstract: Near‐Infrared‐Excited FT‐Raman Spectra of Covalently Linked Porphyrin‐ Nitrobenzene Compounds

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ChemInform Abstract: Selective Functionalization. Part 11. Selective Hydrogenation by a Novel Palladium Salicylidene‐ethylenediamine Complex and the Properties of Derivatives of Some Square Planar Homogeneous Hydrogenation Catalysts.

AbstractAnalogues of two reported homogeneous hydrogenation catalysts based upon square planar Pd complexes, e.g. the compounds (V)‐(VII), are prepared; however, no useful catalytic activity of these complexes is found for the reduction of the model compound nitrobenzene to aniline.

Toxicity of nitrobenzene compounds towards isolated hepatocytes: dependence on reduction potential

1. The cytotoxicity of p-substituted nitrobenzenes towards isolated hepatocytes under aerobic or hypoxic conditions has been determined. The nitrobenzene concentration required to cause 50% cytoxicity in 2 h was a function of the one-electron reduction potential of the nitrobenzene, with the more cytotoxic compounds having the strongest electron-withdrawing substituents. 2. The effectiveness of the nitrobenzenes at causing cytotoxicity under aerobic but not hypoxic conditions was markedly increased if hepatocyte catalase was inhibited with azide. 3. Nitrobenzenes at cytotoxic concentrations induced cyanide-resistant respiration in isolated hepatocytes. Their effectiveness correlated with their cytotoxicity. 4. The rate of oxygen activation of these nitrobenzenes by ascorbate was also a function of the one-electron reduction potential. The nitro compounds with the strongest electron-withdrawing substituents were the most rapidly reduced. 5. Most nitrobenzenes were more cytotoxic under aerobic than hypoxic conditions. Ascorbate enhanced hypoxic, but not aerobic, cytotoxicity. 6. It was concluded that the cytotoxicity of different nitrobenzenes is related to their ease of reduction to nitro radical anions and nitrosobenzenes. Aerobic cytotoxicity is probably initiated by redox cycling and oxygen activation by the nitro radical anions whereas hypoxic cytotoxicity is probably initiated by the alkylation of macromolecules by nitrosobenzene metabolites.

Percutaneous Absorption of Nitroaromatic Compounds: In Vivo and In Vitro Studies in the Human and Monkey

The percutaneous absorption of 2-nitro-p-phenylene-diamine, 4-amino-2-nitrophenol, nitrobenzene, p-nitroaniline, and 2,4-dinitrochlorobenzene was measured through human and monkey skin. Human studies were performed with excised skin in diffusion cells. Absorption through monkey skin was measured by in vivo and in vitro techniques. Results were compared with those from previously reported human in vivo studies on 2,4-dinitrochlorobenzene and nitrobenzene. Rapid penetration was observed with all compounds, with maximum absorption occurring the first few hours. No significant differences in absorption were found in values obtained by the different procedures except for the highly volatile (and therefore difficult to compare) compound nitrobenzene. A comparison of the human and monkey in vitro data showed a trend toward increased absorption through monkey skin, but the increase was not statistically significant. The monkey in vivo and in vitro results showed that absorption of all compounds except nitrobenzene was slightly less in the in vitro studies; however, the values were not significantly different. The relative volatility of these nitroaromatic compounds was measured by the loss of compound from epidermal discs at various time intervals. The greatest loss of applied material occurred with nitrobenzene; however, substantial amounts of the other compounds were lost, particularly during the first minute after application as the acetone vehicle evaporated. Monkey skin was found to be a good model for human skin for the determination of the percutaneous absorption of these compounds, and in vitro measurements of absorption agreed reasonably well with values obtained by in vivo techniques. A good correlation was not observed between the absorption of these compounds and their solubility properties.

Dipolar association as a function of molecular structure studied by nonlinear dielectric effect

Nonlinear dielectric effect (NDE) and molecular association are studied in the aromatic compounds nitrobenzene, phenylisothiocyanate and benzonitrile as well as their saturated analogs nitrocyclohexane, methylisothiocyanate and acetonitrile in nonpolar solvents. Both NDE and the energy of association (dimerization) Δ G are found to be dependent on molecular structure: more readily associating aromatic compounds exhibit greater Δ G values than their saturated analogs; this is apparent as a characteristic Δε/E2 dependence on the concentration in nonpolar solvents (“nitrobenzene type” curve).

Investigation of short lived radicals in aromatic nucleophilic substitution by use of nitroso compounds as scavengers

Radical intermediates formed in reaction of substituted nitrobenzene compounds with nucleophilic reagents have been trapped by t-nitrosobutane to yield nitroxide radicals which have been characterized in situ by ESR. The formation of short-lived radicals originating from reagents and solvents has been shown.

Remarks on donor-acceptor interaction in molecules of nitrobenzyl compounds

The groups YHg, CH3 and R2NCH2 in the p-derivatives of nitrobenzene have very little effect on the spectra of the nitrobenzene compounds, while the R2N group has a strong effect, and the YHgCH2 occupies an intermediate position. This relates not only to the effect of the frequency and intensity of the infrared absorption bands of the nitro group and on the first intense long-wave band in the ultraviolet spectrum, but also to the sensitivity of these parameters to the effect of intermolecular reaction. It is possible that solvation of the YHgCH2 group occurs, accompanied by an increase in its electron-donor capacity.

The controlled potential coulometric and controlled potential polarographic determinations of substituted nitrobenzene compounds in dimethylsulfoxide

The n-values for the reduction of the isomers of nitrophenol and nitrobenzoic acid and for several other nitro compounds were determined in dimethylsulfoxide by controlled potential coulometry. A procedure is given in which one μmole of nitro compound may be determined in less than 8 min with an error of approximately ±l%. The associated background currents were quantitatively evaluated, and electrolysis conditions for their minimization were discussed. A procedure and results are given for the controlled potential polarography of these nitro compounds in dimethylsulfoxide.