Showing papers on "Nitrobenzene published in 1993"

An investigation of titanium dioxide photocatalysis for the treatment of water contaminated with metals and organic chemicals

Abstract: Laboratory experiments were performed to investigate TiO 2 photocatalysis for treating water contaminated with dissolved metals (Ag, Au, Cd, Cr, Cu, Hg, Ni, and Pt) and a variety of organics (e.g., methanol, formic acid, salicylic acid, EDTA, phenol, and nitrobenzene). It was found that only those metals with half-reaction standard reduction potentials more positive than 0.3 V (vs normal hydrogen electrode) can be treated using TiO 2 as the photocatalyst. Kinetic data illustrating the synergism between oxidation and reduction are presented. Experiments using singly substituted benzenes as electron donors show that the rate of reduction of Cr(VI) is correlated with Hammett a constants

Degradation of nitrobenzene by a Pseudomonas pseudoalcaligenes.

Abstract: A Pseudomonas pseudoalcaligenes able to use nitrobenzene as the sole source of carbon, nitrogen, and energy was isolated from soil and groundwater contaminated with nitrobenzene. The range of aromatic substrates able to support growth was limited to nitrobenzene, hydroxylaminobenzene, and 2-aminophenol. Washed suspensions of nitrobenzene-grown cells removed nitrobenzene from culture fluids with the concomitant release of ammonia. Nitrobenzene, nitrosobenzene, hydroxylaminobenzene, and 2-aminophenol stimulated oxygen uptake in resting cells and in extracts of nitrobenzene-grown cells. Under aerobic and anaerobic conditions, crude extracts converted nitrobenzene to 2-aminophenol with oxidation of 2 mol of NADPH. Ring cleavage, which required ferrous iron, produced a transient yellow product with a maximum A380. In the presence of NAD, the product disappeared and NADH was produced. In the absence of NAD, the ring fission product was spontaneously converted to picolinic acid, which was not further metabolized. These results indicate that the catabolic pathway involves the reduction of nitrobenzene to nitrosobenzene and then to hydroxylaminobenzene; each of these steps requires 1 mol of NADPH. An enzyme-mediated Bamberger-like rearrangement converts hydroxylaminobenzene to 2-aminophenol, which then undergoes meta ring cleavage to 2-aminomuconic semialdehyde. The mechanism for release of ammonia and subsequent metabolism are under investigation.

Biodegradation of nitrobenzene by a sequential anaerobic-aerobic process

Abstract: Nitrobenzene was completely degraded by mixed cultures using a sequential anaerobic-aerobic treatment process. Under anaerobic conditions in a fixed-bed column aniline was formed from nitrobenzene through gratuitous reduction by cells of sewage sludge. This reaction was accelerated by the addition of glucose. Complete mineralization of aniline was accomplished by subsequent aerobic treatment using activated sludge as inoculum. The maximum degradation rate of nitrobenzene (4.5 mM) in the two-stage system was 552 mg l−1d−1, referring to 154 mg of nitrobenzene per gram of glucose. In a second experimental phase glucose as cosubstrate and H-donor was replaced by synthetic waste containing ethanol, methanol, isopropanol and acetone. Again, nitrobenzene (1.9 mM) was completely degraded (maximum degradation rate of 237 mg l−d−1, referring to 251 mg per gram of solvents). The major advantage of the described two-stage process is that the reduction of nitrobenzene by anaerobic pretreatment drastically reduces emission by stripping during aerobic treatment.

A novel membrane bioreactor for detoxifying industrial wastewater: II. Biodegradation of 3‐chloronitrobenzene in an industrially produced wastewater

Abstract: A novel membrane bioreactor has been used for the treatment of an industrially produced wastewater arising in the manufacture of 3-chloronitrobenzene. This wastewater is not amenable to direct biological treatment without some form pretreatment or dilution, due to the inorganic composition (pH <1, salt concentration 4% w/w) of the wastewater. In the membrane bioreactor, the organic pollutants are first separated from the wastewater by selective membrane permeation, and then biodegraded in the biological growth compartment of the bioreactor. At a wastewater flow rate of 64 mL h−1 (corresponding to a contact time of approximately 1.7 hours) over 99% of the 3-chloronitrobenzene and over 99% of the nitrobenzene in the wastewater were degraded. Degradation of 3-chloronitrobenzene was accompanied by evolution of chloride ions in a stoichiometric ratio. Both 3-chloronitrobenzene and nitrobenzene degradation were accompanied by the evolution of carbon dioxide; approximately 80% of the carbon entering the system was oxidized to CO2 carbon. Analysis of mass transport across the membrane revealed that 3-chloronitrobenzene and nitrobenzene are transported more rapidly than phenol. This is explained in terms of a resistances-in-series model, which shows phenol transfer to be rate limited by the membrane diffusion step, whereas the chloronitrobenzene and nitrobenzene transfer are rate limited by the liquid film mass transfer. © 1993 Wiley & Sons, Inc.

The Extraction of Strontium and Barium with a Solution of Bis-1,2-Dicarbollylcobaltate in Nitrobenzene in the Presence of 18-Crown-6

Abstract: A study has been made of the extraction of Sr and Ba in an aqueous solution of perchloric acid-18-crown-6-bis-1,2-dicarbollylcobaltate-nitrobenzene. It was found that the organic phase contains complexes of the ML2+org type ( M = Sr2+, Ba2+) that are converted to ML22+org when the concentration of crown (cL) is greater than the concentration of bis-1,2-dicarbollylcobaltate (cB). The values of the corresponding extraction constants, individual extraction constants and stability constants of the extracted species in the organic phase were determined. The system can be utilized for separation applications at concentrations here cL < cB.

Electrophilic aromatic Cl+ addition and CO˙+ substitution in the gas phase

Abstract: Chlorine cation addition to benzene, aniline, anisole, styrene, chlorobenzene, and nitrobenzene was studied using NH 3 Cl + , ClC≡O + , protonated CH 3 Cl, and Cl + as reagent ions. The reactions of protonated monochloramine were followed using a direct insertion membrane probe for sample introduction and a pentaquadrupole mass spectrometer for product characterization. The other reagent ions ClC≡O + , Cl + , and protonated CH 3 Cl were generated by electron ionization of acetyl chloride and carbon tetrachloride and by methane chemical ionization of CH 3 Cl, respectively

Cavitands as selective materials for QMB sensors for nitrobenzene and other aromatic vapours

Abstract: The sensitivity of vase-like cavitands to nitrobenzene and other organic and inorganic vapours has been investigated by using the technique of the quartz microbalance (QMB) in order to determine the variation of the mass adsorbed. Cavitands at room temperature showed a high selectivity to nitrobenzene with respect to benzene and other organic vapours like toluene, fluorobenzene and carbon tetrachloride. This material is insensitive towards other vapours, present in a concentration of 1000 ppm, like H 2 , CO, SO 2 , H 2 S, NO and NO 2 , an it is also insensitive to relative humidities up to 90%. The X-ray structure analysis of the host—guest complex with the fluorobenzene is also described.

Amination of nitrobenzene via nucleophilic aromatic substitution for hydrogen: direct formation of aromatic amide bonds

Abstract: The first example of the direct formation of aromatic amide bonds via nucleophilic aromatic substitution for hydrogen is described. Thus, the reaction of benzamide, tetramethylammonium hydroxide dihydrate, and nitrobenzene under anaerobic conditions generates N-(4-nitrophenyl)-benzamide (1) (98%) and azoxybenzene (30%) in isolated yields. In addition, other substituted benzamides and aliphatic amides are shown to function as nucleophiles in this reaction. A mechanism that is consistent with the simultaneous formation of anilide products and azoxybenzene which requires the oxidation of α-complex intermediates by nitrobenzene initially generating nitrobenzene radical anions is proposed. By contrast, when the reaction is run under aerobic conditions, the formation of azoxybenzene is completely inhibited due to the trapping of nitroarene radicals by O 2 . The ability to prepare (1) in high yield and regioselectivity affotds a nouvel route for the direct amination of nitrobenzene that does not require halogenated intermediated or auxiliary leaving groups. Accordingly, treatment of (1) with methanolic ammonia results in the aminolysis of the amide bond producing 4-nitroaniline and regenerates benzamide

Photocatalytic destruction of hazardous chlorine‐ or nitrogen‐containing aromatics in water

Abstract: To more precisely assess the destruction of organic micropollu‐tants in water by UV‐illuminated TiO2 in the presence of oxygen (air), we have studied the degradation of chlorophenols (CPs), 2,4‐dichlorophenoxyethanoic acid (2,4‐D), benzamide (BZA) and nitrobenzene (NBz) as typical monoaromatic pollutants containing chlorine or nitrogen atoms The beneficial effect of TiO2 (Degussa P‐25) was demonstrated by comparison with direct photolysis in various UV spectral regions Efficiencies of the TiO2‐UV, H2O2‐UV (>220 nm) and H2O2‐Fe2+ systems for the elimination of BZA have been compared The effect of the radiant flux on the elimination of monochlorophenols indicated that the recombination rate of photoproduced charges easily predominates over the pollutant oxidation rate This leads to apparent quantum yields of the order of 10‐2 at 365 nm for a flux of photons/s potentially ab‐sorbable by TiO2 of ca 5 × 1016 and an initial concentration of 0155 mM at pH 45 Common anions do not produce redhibit

Methodology Of Ozone Introduction Into Water And Wastewater Treatment

Abstract: Theoretical basis and methodology for calculation and modeling of ozonation processes and contact equipment have been elaborated. Methodology of determination of reaction rate constant, stoichiometric coefficient, optimum values of pH, intermediate and final products, regimes of chemisorption, etc., for certain typical fast and slow reacting organic compounds (aniline, toluidine, humic acids, nitrobenzene, glyoxalic, oxalic and acetic acid) and wastewaters have been proposed. For calculation of the wastewater ozonation process, the value of chemical oxygen demand (COD) was suggested to be as a kinetic parameter from the solution side. On the basis of kinetic information, recommendations for the choice of the construction of contact equipment for the different chemisorption regimes of ozonation have been presented. Some new contact apparatuses have been proposed.

Selective inclusion by cholic acid

Abstract: Crystallographic, thermodynamic and molecular mechanics results show that cholic acid enclathrates nitrobenzene in preference to aniline.

Solvent extraction separation of uranium(VI) with dibenzo-24-crown-8

Abstract: Uranium(VI) was quantitatively extracted with 0.01M DB-24-crown-8 in nitrobenzene from 6 to 10M hydrochloric acid. From the organic phase uranium was stripped with 2M nitric acid and determined spectrophotometrically with PAR at 530 nm. Uranium(VI) was separated from a large number of elements in binary mixtures as well as from multicomponent mixtures. The method was extended to the analysis of uranium in geological samples and animal bone.

Oxidation of aniline to nitrobenzene by nonheme bromoperoxidase.

Abstract: Nonheme bromoperoxidase found in Pseudomonas putida catalyzed the bromination of aniline with hydrogen peroxide and bromide ions to give o- and p-bromoanilines. However, in the absence of bromide ions, it oxidized aniline via azobenzene and azoxybenzene finally into nitrobenzene. This is the first report of the biological oxidation of an arylamine to the corresponding nitrocompound at the enzyme level. In addition, nitrobenzene was not formed by a nonheme bromoperoxidase from Corallina pilulifera (marine alga), implying that the alga enzyme has a different reaction mechanism.

Gibbs energies, entropies and enthalpies of transfer for monovalent cations from acetonitrile to several solvents

Abstract: Polarographic half-wave potentials and their temperature dependences have been measured for the cations Li+, Na+, K+, Rb+, Cs+, Ag+, Tl+ and Cu+ in up to 22 solvents. Gibbs energies of transfer were derived from reversible polarographic half-wave potentials via the bis(biphenyl)chromium assumption, entropies of transfer were calculated from temperature coefficients on the basis of a negligible thermal diffusion potential and enthalpies of transfer from the equation ΔtH°=ΔtG°+TΔtS°. Single-ion transfer properties from acetonitrile into the solvents water, methanol, ethanol, trifluoroethanol, propan-1-ol, butan-1-ol, hexan-1-ol, ethane-1,2-diol, phenylethanol, benzaldehyde, formic acid, acetic acid, propylene carbonate, trimethylphosphate, formamide, N-methylformamide, N,N-dimethylformamide, N-methyl-2-pyrrolidone, hexamethylphosphoric triamide, nitrobenzene, dimethyl sulfoxide, acetonitrile, propanenitrile, butanenitrile, benzonitrile, pyridine, pyrrole, aniline, mercaptoethanol, thiophenol, N,N-dimethylthioformamide and N-methyl-2-thiopyrrolidone are reported.The entropies of transfer as well as the TΔtS° values of these cations were found to be linearly dependent on each other with slopes close to unity. An ordering of the solvents with respect to the entropies of transfer based on average values for the cations investigated is proposed, since no correlations between the TΔtS° values for these cations and solvent parameters reflecting either physical, macroscopic or microscopic solvent properties were found.

A highly active palladium complex catalyst in the synthesis of N,N′-diphenylurea from nitrobenzene, aniline and carbon monoxide

Abstract: A catalyst system comprising palladium acetate and bidentate bis(diphenylphosphino)alkane ligand of general formula Ph2P(CH2)nPPh2 (n = 3–5) was highly active in N,N′-diphenylurea synthesis from nitrobenzene, aniline and carbon monoxide and showed different reactivity from the system with the more common monodentate triphenylphosphine ligand.

Catalytic vapour-phase nitration of benzene over modified Y zeolites: influence of catalyst treatment

Abstract: The catalytic vapour-phase nitration of benzene with aqueous nitric acid has been carried out on modified Y zeolites. The influence of various ultrastabilization and activation procedures on the catalytic activity and stability of the materials was investigated. The modified Y zeolites were characterized by physico-chemical methods, and correlations between catalyst properties and catalytic performance are discussed. It was found that modified Y zeolites are active catalysts for the vapour-phase nitration of benzene, and that both nitrobenzene space time yield and catalytic stability are strongly dependent on the preparation procedure. Thus, stable catalysts for the vapour-phase nitration of benzene were obtained by acid treatment of low sodium ultrastabilized Y zeolites.

Electrophilic bromination of gaseous aromatic compounds: mechanism and linear free energy effects on reaction rates

Abstract: Electrophilic bromination of monosubstituted aromatic compounds is effected in a pentaquadrupole mass spectrometer using BrCO+ and CH3NH2Br+ as mass-selected reagent ions. Reaction normally occurs at the ring and the brominated product can be mass selected in turn and caused to dissociate by Br˙ loss upon collision-induced dissociation. Linear free energy correlations with Brown substituent σ+ constants describe the extent of gas-phase bromine cation addition under the non-equilibrium, low-pressure and solvent-free conditions which pertain in quadruple collision cells. The electrophilic addition reaction proceeds via a σ-complex to the ring as suggested by MS3 spectra, except in the case of nitrobenzene, where substituent bromination is suggested by the occurrence of a competitive process in which the nitrosubstituent is displaced by bromine. The reactivity parameters ρ are −0.23 and −0.56 for the gaseous reagents, BrCO+ and CH3NH2Br+, respectively. Both values are much less negative than corresponding values for bromination in solution. The greater reactivity of BrCO+ is evident by the fact that it reacts even with the strongly deactivated substrates and this is consistent with a weak BrCO bond. Competitive protonation occurs in the case of CH3NH2Br+ and, unlike bromination, the rate of this reaction does not correlate with σ+ values. This is suggested to be a consequence of protonation at the ring in some cases and at the substituent in others, including acetophenone and benzonitrile. Evidence for this is that, in contrast to its lack of correlation with substituent constants, the rate of protonation correlates linearly with proton affinity.

A Hydrophobicity Scale of Heteropoly- and Isopolyanions Based on Voltammetric Studies of Their Transfer at the Nitrobenzene/Water Interface.

Abstract: A hydrophobicity scale of heteropoly- and isopolyanions is proposed on the basis of voltammetric studies concerning their transfer at the nitrobenzene (NB)/water (W) interface. For polyanions of various size and ionic charge (z = −2 to −6), the standard ion-transfer potential (ΔOWφ), which is related to the Gibbs free energy of the transfer as ΔOWφ = −ΔGtrO→W/zF (F, the Faraday constant), depends linearly on the quantity |z|/n2/3 (n, the number of oxygen atoms in the polyanion structure), which should be proportional to the surface charge density of the polyanion. The value of |z|/n2/3 may provide a useful criterion for evaluating the hydrophobic (or hydrophilic) properties of polyanions, including the stability in solutions and extractability into organic solvents.

Infrared multiple-photon dissociation of the nitrobenzene radical cation. A paradigm for competitive reactions

Abstract: The dissociation of nitrobenzene cation displays a variety of surprising and even apparently nonstatistical reaction behaviors. We have used infrared multiple-photon dissociation experiments to further study the reactions of this system. These experiments along with a previous photoelectron photoion coincidence study indicate that, for some products, the nitrobenzene cation dissociates to form an ion-neutral complex and then reassociates to give the phenyl nitrite cation. A reaction mechanism involving statistical dissociation is shown to account for the experimental data

Nonionic Organic Partitioning onto Organoclays

Abstract: The adsorption of two nonionic organic compounds, nitrobenzene (NB) and 1,2-dichlorobenzene (DCB) onto five organoclays was studied. The results of the adsorption studies were compared to ...

Application of the Solid Polymer Electrolyte Method to Organic Electrochemistry XIV . Effects of Solvents on the Electroreduction of Nitrobenzene on Cu, Pt‐Nafion

Abstract: The effects of solvents on the electroreduction of nitrobenzene on Cu, Pt‐Nafion were investigated. The presence of a sufficient amount of a cosolvent in the catholyte or in the anolyte facilitated the reduction of nitrobenzene to aniline. Without a sufficient amount of a cosolvent, the mass transfer of nitrobenzene to the active sites on the cathode was suppressed, and hydrogen evolution became significant. The solubility parameter value, , of the catholyte is an important index for predicting the effectiveness of mass transfer of nitrobenzene to the active sites of the solid polymer electrolyte composite electrode. When an aqueous solution was used as the anolyte, catholytes with were effective for aniline production by the electroreduction of nitrobenzene on Cu, Pt‐Nafion.

Removal of Organic Compounds from Water via Cloud-Point Extraction with Permethyl Hydroxypropyl-β-cyclodextrin

Abstract: Aqueous solutions of nonionic surfactants are known to undergo phase separations at elevated temperatures. This phenomenon is known as “clouding,” and the temperature at which it occurs is referred to as the cloud point. Permethyl-hydroxypropyl-β-cyclodextrin (PMHP-β-CD) was synthesized and aqueous solutions containing it were found to undergo similar cloud-point behavior. Factors that affect the phase separation of PMHP-β-CD were investigated. Subsequently, the cloud-point extractions of several aromatic compounds (i.e., acetanilide, aniline, 2,2′-dihydroxybiphenyl, N-methylaniline, 2-naphthol, o-nitroaniline, m-nitroaniline, p-nitroaniline, nitrobenzene, o-nitrophenol, m-nitrophenol, p-nitrophenol, 4-phenazophenol, 3-phenylphenol, and 2-phenylbenzimidazole) from dilute aqueous solution were evaluated. Although the extraction efficiency of the compounds varied, most can be quantitatively extracted if sufficient PMHP-β-CD is used. For those few compounds that are not extracted (e.g., o-nitroaceta...

Dalton communications. Organic nitro compounds as ligands. A comparison between the ligand behaviour of MeNO2 and PhNO2 towards AlCl3

Abstract: The crystal-structure analyses of the complexes [AlCl3(RNO2)](R = Me or Ph) and NMR data in solution suggest a stronger Al–O co-ordinative interaction in the case of nitrobenzene compared to nitromethane; this could account for the dramatic solvent effects observed during certain electrophilic acylation processes involving AlCl3 as a promoter.

Catalyst for the preparation of aniline

Abstract: A process for the preparation of aniline by hydrogenation of nitrobenzene in the gas phase in the presence of a catalyst containing a noble metal is described. The process can be carried out in an improved manner if the catalyst employed is palladium on graphite or petrol coke, as the support, containing 0.001-1% by weight of Pd, based on the total weight of the catalyst, it being possible for the catalyst also to contain, in addition to the Pd, 0.001-0.5% by weight of Ir and/or 0.001-0.3% by weight of Rh, all figures being based on the total weight of the catalyst.

Polarization-corrected electrostatic potentials of aromatic compounds

Abstract: The electrostatic potentials (EPS) corrected for polarization (TPS) of the aromatic compounds benzene, aniline, chlorobenzene, nitrobenzene, phenol, benzamide, and N-phenylacetamide have been calculated at the ab initio SCF level within three basis sets: 6-31G**, MINI-1, and STO-3G For chlorobenzene in its MINI-1-optimized geometry, the calculation was also performed within MINI-1** By reference to 6-31G**, the MINI-1-computed EP is much more satisfactory than the STO-3G-computed EP, whereas the MINI-1 and STO-3G basis sets give very similar total potentials corrected for polarization (TPs) The MINI-1** basis set appears to be miscalibrated for computing EPs It provides qualitative results that differ from those obtained with the 6-31G** basis set The EP has a negative well above the middle of the benzene ring, while the TP exhibits a negative crown just above the benzene carbon atoms, where electrophilic attack takes place The TP calculated for the interaction of nitrobenzene with a hydride ion instead of a proton allowed analyzation of the effects of polarization on the positive EP above the N-C bond

Positron annihilation spectroscopy study of moisture absorption in protective epoxy coatings

Abstract: Position annihilation spectroscopy (PAS) was used to measure the relative free-volume fraction of protective epoxy coatings before and after exposure to liquid water at room temperature. The relative free volume fraction determined before water exposure was compared to the equilibrium water uptake of each coating and a correlation was found. The relative free-volume fraction of the epoxy coatings decreased slightly after water exposure. This decrease is contrary to the free volume theory of plasticization, but is consistent with the antiplasticization process. Larger decreases in the relative free volume fraction were sought by repeating the water uptake experiments with nitrobenzene which in the bulk, liquid form quenches ortho-positronium (o-Ps). Since the o-Ps lifetime remained approximately constant and the o-Ps intensity decreased after nitrobenzene absorption, nitrcbenzene is believed to be inhibiting the formation of o-Ps in the epoxy free volume cavities. Larger decreases in the relative free volume fractions were found after nitrobenzene exposure than after water exposure. These larger decreases are due to the fact that nitrobenzene is a better inhibitor of o-Ps formation than water in the epoxy free volume cavities. Larger volume fractions of nitrobenzene were absorbed by the coatings than water and were interpreted to be due to interactions between nitrobenzene and the epoxies. © 1993 John Wiley & Sons, Inc.