Showing papers on "Nitrobenzene published in 1999"
TL;DR: In this article, a well dispersed and stable colloidal dispersions of polymer-protected Ni/Pd bimetallic nanoclusters have been obtained over an entire composition range by an improved polyol reduction method, in which nickel sulfate and palladium(II) acetate were reduced at high temperature by ethylene glycol in the presence of poly(N-vinyl-2pyrrolidone).
Abstract: Well-dispersed and stable colloidal dispersions of polymer-protected Ni/Pd bimetallic nanoclusters have been obtained over an entire composition range by an improved polyol reduction method, in which nickel(II) sulfate and palladium(II) acetate were reduced at high temperature by ethylene glycol in the presence of poly(N-vinyl-2-pyrrolidone). Transmission electron microscopy indicates that these bimetallic nanocluster particles have definitely monodispersed size-distributions, with each particle containing both nickel and palladium atoms. The alloy structure has also been shown by X-ray diffraction and extended X-ray absorption fine-structure analysis. X-ray absorption near-edge spectroscopic and X-ray photoelectron spectroscopic data have confirmed that the nickel in the bimetallic nanoclusters is in the zero-valence state, as stabilized by the presence of Pd. Dispersions of these bimetallic nanoclusters were used as homogeneous catalysts for hydrogenation of nitrobenzene at 30 °C under an atmospheric pr...
271 citations
TL;DR: In this paper, a single-step catalytic hydrogenation of nitrobenzene in acid medium is described, which achieves selectivity to p-aminophenol as high as 75% under the best set of conditions.
208 citations
TL;DR: In this article, surface and interfacial tension in systems formed by Brazilian crude oil n-pentane insolubles (C5I) and n-heptane (C7I) in the aromatic solvents toluene, pyridine, and nitrobenzene were measured at room temperature using the ring method and employing an automatic tensiometer.
Abstract: Data on the behavior of crude oil n-pentane- and n-heptane-insoluble fractions in aromatic solvent systems were obtained. Surface and interfacial tensions in systems formed by Brazilian crude oil n-pentane insolubles (C5I) and n-heptane insolubles (C7I) in the aromatic solvents toluene, pyridine, and nitrobenzene were measured at room temperature using the ring method and employing an automatic tensiometer. The results indicated possible asphaltene aggregation as well as the probable existence of critical micelle concentrations for both C5I and C7I fractions in each of the three solvents considered. Critical micelle concentrations measured for the C5I fraction in toluene and pyridine solutions were consistently higher than those in systems containing the C7I fraction, indicating a lower association tendency in the C5I fraction. Average molecular areas for asphaltenes adsorbed at different interfaces estimated from surface tension measurements were found to be in agreement with literature values and appear...
100 citations
TL;DR: In this article, a kinetic model for the advanced oxidation of aromatic hydrocarbons in water is proposed and tested with experimental results of the oxidation of nitrobenzene and phenanthrene.
Abstract: A kinetic model for the advanced oxidation (ozonation alone, UV radiation alone, ozone plus hydrogen peroxide, ozone plus UV radiation, and UV radiation plus hydrogen peroxide) of aromatic hydrocarbons in water is proposed and tested with experimental results of the oxidation of nitrobenzene and phenanthrene, two aromatic hydrocarbons of different reactivity with ozone. The kinetic model leads to good results in the case that the compound treated reacts exclusively with ozone, that is, without the contribution of hydroxyl radical oxidation as in the case of phenanthrene oxidation. In this case, it is not necessary to account for intermediate reactions to have good predictions of experimental remaining concentrations of ozonation processes. On the contrary, when the aromatic hydrocarbon s mainly removed by hydroxyl radicals (case of nitrobenzene), mole balance equations of intermediates have to be included for the experimental concentrations to be reproduced. For so doing, the kinetic parameters, such as rate constants of reactions between ozone and hydroxyl radical with intermediates and their corresponding quantum yields at 254 nm, were also determined. The kinetic model, however, is unable to reproduce, with accuracy, the experimental results of the ozone-UV radiation oxidation system.
80 citations
TL;DR: Bacterial strain LW1 utilizes 1-chloro-4-nitrobenzene (1C4NB) as a sole source of carbon, nitrogen, and energy and transformation indicated that there was partial reduction of the nitro group to the hydroxylamino substituent, followed by Bamberger rearrangement.
Abstract: Bacterial strain LW1, which belongs to the family Comamonadaceae, utilizes 1-chloro-4-nitrobenzene (1C4NB) as a sole source of carbon, nitrogen, and energy. Suspensions of 1C4NB-grown cells removed 1C4NB from culture fluids, and there was a concomitant release of ammonia and chloride. Under anaerobic conditions LW1 transformed 1C4NB into a product which was identified as 2-amino-5-chlorophenol by 1H and 13C nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry. This transformation indicated that there was partial reduction of the nitro group to the hydroxylamino substituent, followed by Bamberger rearrangement. In the presence of oxygen but in the absence of NAD, fast transformation of 2-amino-5-chlorophenol into a transiently stable yellow product was observed with resting cells and cell extracts. This compound exhibited an absorption maximum at 395 nm and was further converted to a dead-end product with maxima at 226 and 272 nm. The compound formed was subsequently identified by 1H and 13C NMR spectroscopy and mass spectrometry as 5-chloropicolinic acid. In contrast, when NAD was added in the presence of oxygen, only minor amounts of 5-chloropicolinic acid were formed, and a new product, which exhibited an absorption maximum at 306 nm, accumulated.
70 citations
TL;DR: In this paper, it was shown that the hydrogenation of nitrobenzene to aniline follows a Langmuir-Hinshelwood mechanism considering the surface reaction of the adsorbed nitrobensene molecule and one hydrogen atom as the rate determining step.
Abstract: The vapour phase hydrogenation of nitrobenzene to aniline is a highly exothermic reaction deactivated by coking of the palladium catalyst supported on α-alumina carrier. For studying the deactivation of the catalyst a catalytic wall reactor was used in order to ensure isothermal reaction conditions for the kinetic measurements. Furthermore, the catalytic wall reactor allowed the determination of axial coke profiles by total carbon analysis of different wall segments. On the assumption that the main reaction and the deactivation of the catalyst can be assumed separable both the steady state and the unsteady state kinetics were studied. Nitrobenzene was identified as the relevant coke precursor whereas aniline has neither an influence on the main reaction nor on the deactivation. It could be shown that the hydrogenation of nitrobenzene to aniline follows a Langmuir–Hinshelwood mechanism considering the surface reaction of the adsorbed nitrobenzene molecule and one adsorbed hydrogen atom as the rate determining step. The differentiation of coke on the active sites and coke on the support must be taken into account to model the kinetics of coke formation with sufficient accuracy.
68 citations
59 citations
TL;DR: In this article, a cycle of benzene with 4-chlorobenzoyl chloride was attempted with different solid acid catalysts such as dodecatungstophosphoric acid (DTPA), DTPA/K-10 clay, K-10, Amberlite, Amberlyst-15, Indion-130, Filtrol-24 clay, and sulfated zirconia.
57 citations
TL;DR: The reductive carbonylation of nitrobenzene catalyzed by selenium to yield unsymmetric phenylureas has been studied in this paper, where secondary amines were used as coreagents, a single product, phnhconr2, was formed.
53 citations
TL;DR: Using a mixture of three mono nitrophenols as sole carbon, nitrogen and energy sources, mixed cultures were enriched from municipal activated sludge to degrade both nitropenols and nitrobenzene to show broad degradation ability.
Abstract: Using a mixture of three mono nitrophenols as sole carbon, nitrogen and energy sources, mixed cultures were enriched from municipal activated sludge to degrade both nitrophenols and nitrobenzene. B...
46 citations
TL;DR: In this paper, a linear sweep voltammetry (LSV) technique was used to study the electrochemical oxidation behavior of salicylic acid, benzoic acid, citric acid, aniline and nitrobenzene.
TL;DR: For 13 dipeptides with un-ionizable amino acid side chains, their transfer at the nitrobenzene/water interface facilitated by dibenzo-18-crown-6 (DB18C6) has been studied by ion transfer voltammetry as mentioned in this paper.
Abstract: For 13 dipeptides with un-ionizable amino acid side chains, their transfer at the nitrobenzene/water interface facilitated by dibenzo-18-crown-6 (DB18C6) has been studied by ion transfer voltammetry On the condition that the pH of the water phase is adequately low compared with the pK1 (=30–33) of the dipeptide, its protonated form transfers across the interface as a univalent cation The reversible half-wave potential determined at pH 23 by cyclic voltammetry has been found to show good correlations with the hydrophobicities of the dipeptides estimated by some previously proposed hydrophobicity scales of amino acid residues Especially, an excellent correlation with R=0991 has been obtained for the “effective’' hydrophobicity scale proposed by Akamatsu and Fujita (J Pharm Sci, 1992, 81, 164), in which the steric effect of amino acid side chains seems to be correctly incorporated
TL;DR: It is suggested that nitrosobenzene can be reduced non-enzymatically by NADH, and the redox cycle reaction resulted in oxidative DNA damage due to the copper-oxygen complex, derived from the reaction of Cu(I) with H2O2.
TL;DR: In this article, surface and interfacial tensions in model systems formed by a Brazilian crude oil n-pentane insolubles (C5I) and n-heptane (C7I) in three different aromatic solvents: toluene, pyridine and nitrobenzene, were measured at room temperature, employing an automatic tensiometer and using the ring method.
Abstract: Surface and interfacial tensions in model systems formed by a Brazilian crude oil n-pentane insolubles (C5I) and n-heptane insolubles (C7I) in three different aromatic solvents: toluene, pyridine and nitrobenzene, were measured at room temperature, employing an automatic tensiometer and using the ring method. The results obtained indicated possible asphaltene aggregation and allowed the determination of critical micelle concentrations (c.m.c) for both C5I and C7I fractions in each of the three solvents considered. In toluene and pyridine solutions, the C5I fraction consistently presented higher c.m.c. values indicating a lower tendency of association for the organic fraction contained in the C5I, and absent in the C7I. In nitrobenzene solutions, this extra organic fraction appears to facilitate asphaltene association, possibly due to the formation of mixed aggregates. Average molecular areas for asphaltenes adsorbed at different interfaces were estimated using measured tensions and found to be in...
TL;DR: Pd(OAc) 2 undergoes easy and quantitative coordination to a cross-linked styrene/divinylbenzene resin functionalized with bis(diphenylphosphino)methane ligands to yield a supported palladium complex which behaves as a versatile and recyclable heterogenized catalyst for the hydrogenation of nitrocompounds and α,β-unsaturated aldehydes under mild conditions as mentioned in this paper.
Abstract: Pd(OAc) 2 undergoes easy and quantitative coordination to a cross-linked styrene/divinylbenzene resin functionalized with bis(diphenylphosphino)methane ligands to yield a supported palladium complex which behaves as a versatile and recyclable heterogenized catalyst for the hydrogenation of nitrocompounds and α,β-unsaturated aldehydes under mild conditions. Whereas nitrobenzene is converted only into aniline, cinnamaldehyde is selectively converted into hydrocinnamaldehyde.
TL;DR: In this paper, the barrier height at 0° was shown to be larger than that at 90° when electron correlation was included, and it was shown that π-stabilisation has a relatively small contribution to the structure of the nitroaromatics, whereas steric repulsion between the ortho-substituents and the oxygen atoms of the NO 2 group are rather significant.
Abstract: Calculation of the barriers and associated one-dimensional torsional potential are performed for internal rotation of the nitro group in nitrobenzene as well as for o -fluoro- and o , o ′-difluoro-nitrobenzenes. It is shown that the presence of substituents in the ortho-positions force the nitro group to rotate about the C–N bond, out of the plane of the benzene ring. In these conjugated molecules, the inclusion of electron correlation is shown to be necessary for reliable barrier prediction. It is found that the π-stabilisation (resonance) has a relatively small contribution to the structure of the nitroaromatics, whereas the steric repulsion between the ortho-substituents and the oxygen atoms of the NO 2 group are rather significant. The interplay between them accounts for the fact that for o , o ′-C 6 H 3 F 2 NO 2 the barrier height at 0° is larger than that at 90° when electron correlation is included.
TL;DR: In this article, the reduction of nitrobenzene at Mo electrodes has been observed over a wide range of pH values from 4.4 to 13.5, and the final reduction product is the four-electron reduction product, namely, phenylhydroxylamine.
Abstract: The reduction of nitrobenzene at Mo electrodes has been observed over a wide range of pH values from 4.4 to 13. Constant potential coulometry in conjunction with cyclic voltammetric studies show that under moderately alkaline and alkaline conditions, the final reduction product is the four‐electron reduction product, namely, phenylhydroxylamine. This is the first report of nitrobenzene reduction at a Mo electrode. © 1999 The Electrochemical Society. All rights reserved.
TL;DR: In this paper, the authors have succeeded in keeping a high nitration activity of the supported sulfuric acid catalyst for more than two months by co-feeding a trace amount of sulfuric acids (H 2 SO 4 /HNO 3 ǫ = 1/5000 (wt. ratio).
Abstract: In the vapor phase nitration of benzene with diluted nitric acid, we have succeeded in keeping a high nitration activity of the supported sulfuric acid catalyst for more than 2 months by co-feeding a trace amount of sulfuric acid (H 2 SO 4 /HNO 3 = 1/5000 (wt. ratio)). The results after 60 days on-stream over 10 wt.%–H 2 SO 4 /SiO 2 catalyst are as follows: yield of nitrobenzene (NB), 93% based on HNO 3 ; selectivity of NB, 97% based on HNO 3 ; productivity of NB (STY), 0.76 kg/kg cat h. These performances were demonstrated in bench scale experiments using molded silica or quartz supports. Finally, nitration reactions of toluene and chlorobenzene were conducted and compared with each other over several solid acid catalysts developed by us.
TL;DR: In this article, a series of electrochemical reductions were carried out in microemulsions with a view to determining the utility of these novel fluids for preparative electrochemistry.
TL;DR: In this article, the electron affinities for a series of methyl benzoates, acetophenones, benzaldehydes, and benzophenones were determined by measuring the electron-transfer equilibria in the gas phase.
Abstract: The electron affinities (EAs) for a series of methyl benzoates, acetophenones, benzaldehydes, and benzophenones were determined by measuring the electron-transfer equilibria in the gas phase. The effect of substituents (X) in the benzene ring on the EAs of this series as well as the nitrobenzene and benzonitrile series were correlated in terms of the Yukawa–Tsuno equation, It has been shown that the r− value, representing the degree of π-delocalization of the negative charge into the substituent (X) at position 4, increases linearly with decreasing EA of the unsubstituted member (X = H) of the respective series, i.e., 0.65 for nitrobenzene vs. 1.05 for benzaldehyde and 1.30 for benzonitrile. This tendency of the r− value leads to the conclusion that the negative charge of a less-stable radical anion is more significantly distributed in the benzene ring than in a stable radical anion, like that of nitrobenzene. Ab initio MO calculations show that when the EA of a Y-substituted benzene decreases, the total ...
TL;DR: In this article, the crystal structure of ferrocenemethylamine hydrochloride (3) is reported, which possesses a layered N-H⋯Cl-H-bonded network, resulting in the formation of 4-and 8-membered rings of alternating nitrogen and chlorine atoms, with an interlayer separation of 9.17 A.
TL;DR: In this paper, the potential of the transfer of substituted β-diketone and 4-acyl-5-pyrazolone anions across a microhole supported water-∣-nitrobenzene microinterface has been studied by cyclic voltammetry.
TL;DR: In this paper, the electroreduction of nitrobenzene has been studied on Au single crystals of (111, (110), (100), and (210) orientations and on Au polycrystals in dilute aqueous perchlorate solution using cyclic voltammetry.
TL;DR: In this paper, the ability to enhance aryl nitro-reduction processes in sediments through electron donor addition was investigated, and the results demonstrate that all electron donors resulted in increased methane production after a lag phase.
TL;DR: In this paper, an ion pair extraction of potassium salts by dicyclohexyl-18-crown-6 (DC18C6) and diphenylthiourea (DPTU) from aqueous phase into nitrobenzene was examined.
Abstract: In combination with an ion pair extraction of potassium salts by dicyclohexyl-18-crown-6 (DC18C6), extraction behavior of anions with a diphenylthiourea (DPTU) from aqueous phase into nitrobenzene has been examined. The extraction selectivity of potassium salts follows a Hofmeister series: NO3->Br->Cl->OAc-. The extractability of KCl by DC18C6 is significantly enhanced upon the addition of DPTU in organic solution. The slope analysis of the extraction equilibrium reveals a 1:1 complex formation between DPTU and Cl-. The hydrogen-bonding interaction of DPTU with Cl- is confirmed by the 1H NMR analysis in d5-nitrobenzene. For qualitative evaluation, solid-liquid extraction of KCl into d5- nitrobenzene containing DPTU and DC18C6 has been examined by 1H NMR analysis. Similar to the liquid-liquid extraction, an efficient synergistic effect of DPTU for the extraction of KCl is clarified.
TL;DR: In this article, the authors investigated the extraction of micro amounts of cesium by the nitrobenzene solution of H+ bis-1,2-dicarbollylcobaltate (H+B−) in the presence of 15-crown-5 (15C5, L) has been investigated.
Abstract: Extraction of microamounts of cesium by the nitrobenzene solution of H+ bis-1,2-dicarbollylcobaltate (H+B−) in the presence of 15-crown-5 (15C5, L) has been investigated. The equilibrium data have been explained assuming the complexes HL+, HL2+, CsL+ and CsL2+ to be extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated with water have been determined.
TL;DR: The various hydrolysis products as well as the ionized antibiotics were studied in voltammetric transfer from water to nitrobenzene using the method of the interface between two immiscible electrolyte solutions (ITIES).It was concluded that this electrochemical method is suitable for the quantification of beta-lactam antibiotics and their hydrolytic products.
Abstract: We report NMR spectra of nitrobenzene-d5 recorded in the presence of strong ac electric fields using a homebuilt probe and electric field amplifier. Pulsed ac electric fields up to 70 kV/cm rms were used, rather than dc fields, to reduce electrode corrosion, electrode polarization, electrical convection, sensitivity to impurities, electrolysis, and heating. A two-dimensional detection method was used in which fields are applied only during the variable delay associated with the indirect dimension. Tensorial interactions are partially recovered due to partial alignment of the polar molecules in the applied electric field. Molecular order parameters of order 10 -4 were observed in these experiments, in agreement with previous work, and followed the expression Smol ∝ E 2 , as expected, where the constant of proportionality describes the effects of the dielectric response of the medium. Deuterium splittings for the ortho- and paradeuterons were in the ratios expected for a 61° relative angle in bond vectors. We observed a strong dependence of the order parameter on concentration: neat nitrobenzene ordered significantly more than did nitrobenzene diluted in a nonpolar solvent. Under the assumption that neat nitrobenzene forms weakly bound clusters with large effective dipole moments, we attempted to rationalize the degree of order for dilute nitrobenzene only in terms of simple electrostatic theories. Onsager’s model involving spherical molecules overestimates the alignment while Scholte’s adaptation of Onsager’s model for elliptical molecules achieves reasonable agreement with our data for dilute nitrobenzene.
TL;DR: In this article, the authors investigated the influence of the presence of various substituted and unsubstituted crown ethers on the extraction of 22Na, 45Ca, 85Sr and 133Ba by the nitrobenzene solution of bis-1,2-dicarbol-lylcobaltate.
Abstract: The extraction of 22Na, 45Ca, 85Sr and 133Ba by the nitrobenzene solution of bis-1,2-dicarbol-lylcobaltate has been investigated and the influence of the presence of various substituted and unsubstituted crown ethers was shown. Extraction of alkali earth ions in absence of crown ethers increases in the sequence Mg2+
TL;DR: In this paper, the authors investigated the extraction of calcium by a nitrobenzene solution of bis-1,2-dicarbollylcobaltate in the presence of 15-crown-5 (15C5, L).
Abstract: Extraction of calcium by a nitrobenzene solution of bis-1,2-dicarbollylcobaltate in the presence of 15-crown-5 (15C5, L) has been investigated. The equilibrium data and the typical maxima concerning the dependence of the Ca distribution ratios on the analytical concentration of 15C5 in the system under study can be explained assuming that the HL+, HL2+ and CaL2+, CaL22+ particles are extracted into the nitrobenzene phase. The values of the corresponding extraction and stability constants of the extracted species in nitrobenzene saturated with water have been determined and the mutual Sr/Ca separation has been discussed