Nitrobenzene

About: Nitrobenzene is a research topic. Over the lifetime, 5285 publications have been published within this topic receiving 83368 citations. The topic is also known as: essence of mirbane & nitrobenzol.

Piezoelectric quartz crystal detection of benzene vapour using chemically modified cyclodextrins

Abstract: Three chemically modified cyclodextrins have been prepared, characterised by n.m.r. spectroscopy, and studied for their possible role as piezoelectric crystal coating detectors towards benzene vapour. 2,6-Per-O-methyl-β-cyclodextrin 3-perbenzoate (DMsCD-B7) is not recommended. 2,6-Per-O-(t-butyldimethylsilyl)-α-cyclodextrin (DSαCD) was found to be the best for the ca. 0.08–ca. 400 mg dm–3 range of benzene vapour in air. 2,6-Per-O-allyl-α-cyclodextrin (DAαCD) is a possible alternative. Both detector systems function for > 20 days. The detectors are selective towards benzene vapour over methane, propane, butane, pentane, ethyne, ammonia, nitrobenzene, and toluene. Toluene gives rise to the most serious interference. For the preferred DSαCD sensor, toluene only gives < 20% of the decrease in frequency observed with the corresponding amount of benzene. However, the interference is slightly greater for the DAαCD sensor.

Reversible chemistry of CO2 in the preparation of fluorescent supramolecular polymers.

Abstract: The chemistry between CO(2) and primary amines was used to construct novel types of supramolecular polymers and networks. Fluorescent self-assembling gel 2 was prepared, which employs both hydrogen bonding and dynamic, thermally reversible carbamate bonds. As precursors, biscalixarenes 1, 3, 4, 6, and 7 were synthesized, which strongly aggregate (K(D) > or = 10(6) M(-1) per capsule) in apolar solution with the formation of linear self-assembling polymers. Polymer 1n possesses CO(2)-philic primary amino groups on the periphery. CO(2) rapidly reacts with chains 1n in apolar solvents and cross-links them with the formation of multiple carbamate salt bridges. Three-dimensional polymeric network 2 was characterized by (13)C NMR spectroscopy and SEM. Addition of competitive solvent breaks hydrogen bonding in 2 but does not influence the carbamate linkers. Carbamate salt 9 was obtained. On the other hand, thermal release of CO(2) from 2 and 9 was easily accomplished (1 h, 100 degrees C) with retaining the hydrogen-bonding capsules. Thus, three-dimensional polymeric networks 2 were transformed back to linear polymeric chains 1n without their breakup. Multiple pyrene fluorophores, attached on the periphery of 2, cause strong fluorescence of the gel with benzene. When approximately 5% nitrobenzene was gelated together with benzene, fluorescence strongly decreases due to the energy transfer from the pyrene donors in gel 2 to trapped nitrobenzene molecules. This opens a way to switchable fluorescent materials.

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

Pt decorated hierarchical Sb2WO6 microspheres as a surface functionalized photocatalyst for the visible-light-driven reduction of nitrobenzene to aniline

Abstract: Optimizing the structure of semiconductor materials and introducing functional metal clusters have emerged as an effective strategy to improve the photocatalytic performances of catalysts through the synergistic effect between metals and supports. In this work, Pt nanocluster decorated hierarchical Sb2WO6 microspheres which are assembled from ultra-thin nanosheets with only 3.3 nm thickness (Pt/SWO-NS) jointly achieve an efficient photocatalytic reduction of nitrobenzene to aniline and show 10 times higher activity than Pt decorated bulk Sb2WO6 (Pt/SWO-bulk). More importantly, the respective roles of SWO-NS and Pt nanoclusters are deeply studied. SWO-NS with a unique 2D structure, abundant unsaturated surface sites and good visible light response would be favorable for stabilizing Pt nanoclusters, adsorbing and activating more nitrobenzene molecules and providing abundant photo-generated electrons. Meanwhile, Pt nanoclusters serve as electron enrichment centers to decompose HCOONH4 to produce rich ·CO2− and active H for reducing the activated nitrobenzene molecules. In addition, on combining coordination chemistry, a possible synergistic mechanism for hierarchical Sb2WO6 microspheres and Pt nanoclusters is proposed to elucidate the efficient reduction of nitrobenzene to aniline. We believe that this work would provide an effective strategy to optimize catalytic performance by the design of applicable nanocomposites with synergistic effects.

Mixture of fuels approach for the synthesis of SrFeO(3-δ) nanocatalyst and its impact on the catalytic reduction of nitrobenzene.

Abstract: A modified solution combustion approach was applied in the synthesis of nanosize SrFeO3-delta (SFO) using single as well as mixture of citric acid, oxalic acid, and glycine as fuels with corresponding metal nitrates as precursors. The synthesized and calcined powders were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis and derivative thermogravimetric analysis (TG-DTG), scanning electron microscopy, transmission electron microscopy, N-2 physisorption methods, and acidic strength by n-butyl amine titration methods. The FT-IR spectra show the lower-frequency band at 599 cm(-1) corresponds to metal-oxygen bond (possible Fe-O stretching frequencies) vibrations for the perovskite-structure compound. TG-DTG confirms the formation temperature of SFO ranging between 850-900 degrees C. XRD results reveal that the use of mixture of fuels in the preparation has effect on the crystallite size of the resultant compound. The average particle size of the samples prepared from single fuels as determined from XRD was similar to 50-35 nm, whereas for samples obtained from mixture of fuels, particles with a size of 30-25 nm were obtained. Specifically, the combination of mixture of fuels for the synthesis of SFO catalysts prevents agglomeration of the particles, which in turn leads to decrease in crystallite size and increase in the surface area of the catalysts. It was also observed that the present approach also impacted the catalytic activity of the SFO in the catalytic reduction of nitrobenzene to azoxybenzene.