Reaction Of Nitrobenzene Research Articles

Reactions of Aromatic Bifunctional Molecules on Silicon Surfaces: Nitrosobenzene and Nitrobenzene

Chemical control of interfaces formed on silicon surfaces is important for many practical applications. In this work, the reaction of nitrosobenzene with a clean Si(100)- 2 × 1 surface by [2 + 2] cycloaddition at room temperature is investigated. This reaction is compared to the 1,3-dipolar cycloaddition reaction of nitrobenzene on the same surface and to the cyclocondensation reaction of nitrobenzene with hydrogen-terminated Si(100) surfaces. Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) methods were used for this study. For both nitrosobenzene and nitrobenzene on Si(100)- 2 × 1, oxygen migrates subsurface, despite substantial kinetic barriers. The effects of oxygen migration are addressed by combining DFT cluster modeling and XPS in the N 1s region. The reaction pathways of these nitrogen-containing bifunctional molecules on a clean Si(100)- 2 × 1 surface lead to the phenylnitrene adduct as the dominant surface species, while ...

Dehydrative Cyclocondensation Reactions on Hydrogen-Terminated Si(100) and Si(111): An ex Situ Tool for the Modification of Semiconductor Surfaces

Dehydrative cyclocondensation processes for semiconductor surface modification can be generally suggested on the basis of well-known condensation schemes; however, in practice this approach for organic functionalization of semiconductors has never been investigated. Here we report the modification of hydrogen-terminated silicon surfaces by cyclocondensation. The cyclocondensation reactions of nitrobenzene with hydrogen-terminated Si(100) and Si(111) surfaces are investigated and paralleled with selected cycloaddition reactions of nitro- and nitrosobenzene with Si(100)-2x1. Infrared spectroscopy is used to confirm the reactions and verify an intact phenyl ring and C-N bond in the reaction products as well as the depletion of surface hydrogen. High resolution N 1s X-ray photoelectron spectroscopy (XPS) suggests that the major product for both cyclocondensation reactions investigated is a nitrosobenzene adduct that can only be formed following water elimination. Both IR and XPS are augmented by density functional theory (DFT) calculations that are also used to investigate the feasibility of several surface reaction pathways, which are insightful in understanding the relative distribution of products found experimentally. This novel surface modification approach will be generally applicable for semiconductor functionalization in a highly selective and easily controlled manner.

Synthesis of p‐aminophenol from the hydrogenation of nitrobenzene over metal–solid acid bifunctional catalyst

AbstractBACKGROUND: A single‐step conversion of nitrobenzene (NB) to p‐aminophenol (PAP) through catalytic hydrogenation is a widely used synthesis route for PAP. The main shortcoming of this route is the use of sulfuric acid for rearrangement of the phenylhydroxylamine (PHA) intermediate. In this paper, S2O82−/ZrO2 (PSZ) solid acid and Pt‐S2O82−/ZrO2 (Pt‐PSZ) bifunctional catalysts were prepared for the synthesis of PAP in non‐acid medium.RESULTS: Calcination temperature has a substantial effect on the acidity, structure and activity for PHA rearrangement of PSZ. The highest PAP yield was 33.8% over PSZ calcined at 823 K when the reaction was carried out in water at 423 K. A high PAP yield of 23.9% was achieved by a single‐step reaction of nitrobenzene over Pt‐PSZ bifunctional catalysts.CONCLUSION: PSZ solid acid exhibits high activity for PHA rearrangement. Perfect tetragonal ZrO2 and much stronger acid sites play important roles in catalytic activity. Inhibiting the hydrogenation activity by reducing the amount of Pt loading on Pt‐PSZ can improve the competition of PHA rearrangement on acid sites with hydrogenation of PHA on metal active sites, resulting in better selectivity to PAP. Copyright © 2008 Society of Chemical Industry

Nitro Group as a Means of Attaching Organic Molecules to Silicon: Nitrobenzene on Si(100)-2 × 1

This paper will present the computational and experimental infrared studies of the reactions of nitrobenzene on a Si(100) surface, a prototypical model reaction for understanding the behavior of bifunctional molecules on semiconductor surfaces. The initial reaction of nitrobenzene with the Si(100)-2 x 1 occurs via 1,3-dipolar cycloaddition of the nitro group to the silicon surface dimer. Computational exploration of the initial adsorption configurations suggests that two stable structures can be formed: one with the phenyl ring essentially perpendicular to the surface; the other one with the tilt angle of approximately 113 degrees with respect to the surface normal. The barrier for converting the latter into the former, more stable by approximately 13 kJ/mol, is 19.1 kJ/mol. Further thermal reactions are analyzed, and the reaction pathways are compared for the computational models with fixed vs relaxed subsurface silicon atoms. While all the surface species resulting from nitrobenzene transformations on the Si(100)-2 x 1 surface studied here are thermodynamically stable, most of the reaction pathways can be ruled out on the basis of the analysis of the transition states leading to these species and on the comparison of predicted and measured vibrational spectra. As a result, the exact adsorption configurations can be pinpointed.

Gas phase synthesis of para-aminophenol from nitrobenzene on Pt/zeolite catalysts

A single-step reaction of nitrobenzene into para-aminophenol was carried out in the gas phase using metal-supported zeolite as a bi-functional catalyst. A significant amount of para-aminophenol was produced with aniline and ortho-aminophenol without using any environmentally undesirable liquid acid. For the selective formation of para-aminophenol, Pt supported on H-ZSM-5 was the best combination of metal and acid catalysts. The selectivity to para-aminophenol depended greatly on the Al concentration of H-ZSM-5; that is, HZSM-5 with intermediate Al concentration gave the highest selectivity. Pt particles on H-ZSM-5 were characterized by the measurements of adsorbed CO, TEM and IR spectra.

Mesoporous carbon nanotubes for use as support in catalysis and as nanosized reactors for one-dimensional inorganic material synthesis

Mesoporous multi-walled carbon nanotubes (MWNTs) with an average inner diameter of about 50 nm were successfully used as a one-dimensional catalyst support either in gas-phase, i.e. selective oxidation of H 2S into elemental sulfur in a thrickle-bed configuration, or in liquid-phase reactions, i.e. selective hydrogenation of nitrobenzene into aniline or Friedel-Crafts benzoylation reactions. On one hand, the combination of the small size, i.e. high external surface area, and of the tube structure, i.e. confinement effect, allowed a significant improvement of the catalytic performance when compared to that obtained on traditional grain shaped catalysts as observed in the selective oxidation of H 2S and the selective hydrogenation of nitrobenzene reactions. On the other hand, the confinement effect induced by the high aspect ratio of the tubes could, in addition, be effectively used for the synthesis of one-dimensional nanowire zeolitic materials under non-hydrothermal macroscopic conditions. Carbon nanotubes template were removed by combustion leaving behind zeolite nanowires which were made up of zeolite particles of about 10–20 nm. The zeolitic catalysts exhibit a high benzoylation activity compared to that of the commercial one due to its high external surface area.

The carbonylation reaction of nitrobenzene to methyl phenylcarbamate: highly efficient promoters for the palladium-phenanthroline catalytic system based on phosphorus acids.

Phenomenal! The activity of the palladium–phenanthroline catalytic system for the carbonylation of nitrobenzene to methyl phenylcarbamate is greatly enhanced by the addition of phosphorus acids. Of those that were studied, the best promoter is the very cheap, easily separable, and nontoxic phosphoric acid.

The Carbonylation Reaction of Nitrobenzene to Methyl Phenylcarbamate: Highly Efficient Promoters for the Palladium–Phenanthroline Catalytic System Based on Phosphorus Acids

Warum in die Ferne schweifen, wenn das Gute liegt so nah: Die Aktivität des Palladium-Phenanthrolin-Katalysatorsystems für die Carbonylierung von Nitrobenzol zu Methylphenylcarbamaten wird durch Zugabe organischer Phosphorsäuren gesteigert – doch ausgerechnet die einfache, dazu billige, leicht abtrennbare und nichttoxische Phosphonsäure H3PO3 erwies sich als bester Zusatz.

Carbonylation of nitrobenzene to N-methyl phenylcarbamate catalyzed by palladium–phenanthroline complexes Bifunctional activation by anthranilic acid

The palladium–phenanthroline catalyzed carbonylation reaction of nitrobenzene to methyl phenylcarbamate is known to be accelerated by both the addition of aniline and a carboxylic acid. Here, we report that combining the acidic and amino function in the same molecule, 2-NH2C6H4COOH, anthranilic acid, an higher activity is observed with respect to the use of simple benzoic acid. The 4-amino isomer does not show the same increased activity.

Electrocatalytic properties of Cu–Zr amorphous alloy towards the electrochemical hydrogenation of nitrobenzene

The Cu–Zr amorphous alloy was studied as an electrocatalyst towards the electrochemical hydrogenation of nitrobenzene. The electrocatalyst was activated by chemical etching in HF solution. Resulted changes in the morphology, chemical composition and crystalline structure of the electrocatalyst surface were characterised by scanning electron microscopy, X-ray diffraction and Auger electron spectroscopy. The electrocatalytic properties of the Cu–Zr amorphous alloy were assessed by voltammetric measurements. Due to the formation and aggregation of Zr residue modified Cu nanocrystals on the surface caused by the selective dissolution of Zr components in the chemical etching, the activated amorphous alloy is an effective electrocatalyst for the electrochemical reduction reaction of nitrobenzene with aniline as the main product. The positive shift of the peak potential and accompanying increase in the value of peak current in voltammograms with increasing Cu content and decreasing Zr content of the alloy surface in the chemical etching are indicative of improved electrocatalytic activity.

Pulse Radiolysis of Supercritical Water. 2. Reaction of Nitrobenzene with Hydrated Electrons and Hydroxyl Radicals

The rate constants for the reactions of nitrobenzene with the hydroxyl radical (OH•) and hydrated electron ((e-)aq) in water have been measured from room temperature to 400 °C using electron pulse radiolysis and transient absorption spectroscopy. The diffusion-limited reaction of nitrobenzene with (e-)aq exhibits temperature-insensitive activation energy up to 300 °C, indicating that the activation energy for electron diffusion remains high over this range. The (e-)aq reactivity is explained as a long-range electron transfer, and the results are interpreted in terms of extended Marcus theory and Smoluchowski relationships. At 380 °C, the rate constant has a density dependence similar to that previously reported for other (e-)aq scavenging reactions. The reaction rate of nitrobenzene with OH• is very insensitive to temperature from room temperature up to 300 °C, in agreement with previous studies. Above 300 °C, the rate constant increases as the critical temperature is approached and exceeded. Time-resolved electronic absorption spectra of the nitrobenzene radiolysis transients reveal complex kinetics involving multiple absorbing species.

Effect of the Polymeric Matrix of a Catalyst on Its Activity in Hydrogenation

The swelling degree of ion-exchange resin AB-17-8-OH and palladium-containing catalysts based on this resin were studied. The effects of the diameter of polymeric support grains and temperature on the activity of the catalysts in model reactions of nitrobenzene and α-nitronaphthalene hydrogenation were investigated. It was found that the catalyst preparation procedure and the particle size appreciably affect the rates of these reactions.

ChemInform Abstract: Reductive Alkylation of Nitrobenzene Promoted by Zinc and Tin in Protic Solvents.

Abstract Barbier-type organometallic reactions of nitrobenzene with organic halides in protic solvents produce directly N , N -dialkylanilines. With allyl bromide, best yields are obtained using zinc in an aqueous monobasic sodium phosphate solution in the presence of cuprous iodide or tin in methanol. The latter procedure is also successful in the case of benzyl bromide and primary alkyl iodides. Control experiments exclude a mechanism of reduction followed by nucleophilic alkylation and show that the reaction is initiated by a nucleophilic attack of the organometallic species on the nitro group. Similar reactions with Grignard reagents under anhydrous conditions are reported to have a completely different outcome.

Reductive alkylation of nitrobenzene promoted by zinc and tin in protic solvents

Barbier-type organometallic reactions of nitrobenzene with organic halides in protic solvents produce directly N, N-dialkylanilines. With allyl bromide, best yields are obtained using zinc in an aqueous monobasic sodium phosphate solution in the presence of cuprous iodide or tin in methanol. The latter procedure is also successful in the case of benzyl bromide and primary alkyl iodides. Control experiments exclude a mechanism of reduction followed by nucleophilic alkylation and show that the reaction is initiated by a nucleophilic attack of the organometallic species on the nitro group. Similar reactions with Grignard reagents under anhydrous conditions are reported to have a completely different outcome.

Kinetic and spectroscopic characterization of intermediates and component interactions in reactions of methane monooxygenase from Methylococcus capsulatus (Bath)

We describe mechanistic studies of the soluble methane monooxygenase (sMMO) enzyme system from Methylococcus capsulatus (Bath). Interactions among the three sMMO components, the hydroxylase (H), reductase (R), and protein B (B), were investigated by monitoring conversion of nitrobenzene to nitrophenol under both single turnover and catalytic conditions. During catalytic turnover, hydroxylation occurs to afford 3-nitrophenol (43%) and 4-nitrophenol (57%), whereas hydroxylation takes place exclusively (> 95%) to give 4-nitrophenol under single turnover conditions in the absence of reductase. Protein B exerts a strong influence on single turnover reactions of nitrobenzene, with optimal rate constants and yields obtained by using 1.5-2 equiv of protein R per equivalent of hydroxylase. The temperature dependence of these kinetic values was determined. Changes in dioxygen concentration and pH, as well as exchange of solvent accessible protons with D{sub 2}O, did not significantly affect the rate constants for either of these processes, the implications of which for the kinetic mechanism are discussed. From the present and related evidence, structures for H{sub peroxo} and Q are proposed. 54 refs., 11 figs., 4 tabs.

ChemInform Abstract: New Reaction of Nitrobenzene: Nucleophilic Addition of Acetophenone to the Nitro Group in the System DMSO‐KOH with Formation of Enaminoketone.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Catalytic hydrogenation over platinum complexes with poly(vinylpyridine)s

Platinum complexes with poly(vinylpyridine) ligands have been studied as catalysts in the reaction of nitrobenzene and 2-propen-1-ol hydrogenation. Pretreatment of the complexes with NaBH 4 causes the reduction of part of platinum into lower valent states (XPS data) and a decrease of catalytic activity of polymer-metal complexes. The structure of polymer ligands and the position of substituents on the pyridine ring of poly(vinylpyridine) have been shown to affect properties of obtained catalysts. A platinum complex with poly(2-methyl-5-vinylpyridine) was active in hydrogenation reaction.

Ultrasonically stimulated electron transfer in organic chemistry. Reaction of nitrobenzene with triphenylmethane and its derivatives

Triphenylmethyl chloride dissolved in nitrobenzene was either heated at 210°C for 8 h or submitted to a sonochemical promoted reaction at the equilibrium temperature of the ultrasonic cleaning bath (40°C) for 30 h. A practically quantitative conversion of organic halide was achieved in the thermal process, whereas in the ultrasound activated process the conversion was 60%. An activation of the thermal reaction by the ultrasound promotion of the reaction of about 10 7 was approximated. The most significant differences between the two reactions are: (i) triphenylcarbinol is the main product in the sonochemical reaction (69.87%), whereas in the thermal process it represents only 1.53%. (ii) Hydrochloric acid is produced in the thermal process, but molecular chlorine in the sonochemical reaction. (iii) In contrast to the thermal process, only minor reduction products of nitrobenzene are observed in the sonochemical reaction. The electron transfer mechanism is discussed, in direct connection with the sonochemical activation of the transfer.

Synthesis of 1-phenyl-3,3-dimethyltriazene 2-oxide and the corresponding triazene from nitro compounds and N-magnesium bromides

The reaction of dimethylnitramine with Ph-N(MgBr)2 gives 1-phenyl-3,3-dimethyl-triazene 2-oxide, which is the first reported triazene 2-oxide. The reaction of nitrobenzene with Me2NNHMgBr gives only the corresponding triazene.

Degradation of aqueous nitrophenols and nitrobenzene by means of the Fenton reaction

The ‘classical’ Fenton reagent ( FeCl 2 H 2 O 2 ) has been successfully applied to the degradation of 2-nitro- (I), 4-nitro- (II) and 2,4-dinitrophenol (III) in aerated aqueous solutions. The rate of the Fenton reaction of nitrobenzene (IV) is slower than those of nitrophenols (I) – (III). The rate of the decomposition of all the compounds (I) – (IV) is dependent on the concentration of the reagents. The mechanism of the reaction is discussed. The Fenton reaction is suggested as a convenient method for the purifications of wastewaters contaminated with nitrophenols, which are toxic pollutants, difficult to decompose by other means.