Search results for "Oxidizing agent"
showing 10 items of 71 documents
A quantitative study of substituent effects on oxidative cyclization of some 2-methylsubstituted aldehydes. Thiosemicarbazones induced by ferric chlo…
1996
In order to gain further mechanistical information about the cyclization of thiosemicarbazones and thiosemicarbazone-type substrates induced by metallic salts as oxidizing agents, we performed the synthesis of substrates 1a-s and a kinetic study of the oxidative cyclization of 1 to 5-imino-Δ2-1,3,4-thiadiazole 2 and 1,2,4-triazoline-5-thione 3 derivatives induced by methanolic ferric chloride solutions. The results of cyclization were compared to those of corresponding semicarbazones. The kinetic data were analyzed by means of the Hammett's equation and ρ values discussed.
ChemInform Abstract: A Quantitative Study of Substituent Effects on Oxidative Cyclization of Some 2-Methylsubstituted Aldehydes. Thiosemicarbazones I…
2010
In order to gain further mechanistical information about the cyclization of thiosemicarbazones and thiosemicarbazone-type substrates induced by metallic salts as oxidizing agents, we performed the synthesis of substrates 1a-s and a kinetic study of the oxidative cyclization of 1 to 5-imino-Δ2-1,3,4-thiadiazole 2 and 1,2,4-triazoline-5-thione 3 derivatives induced by methanolic ferric chloride solutions. The results of cyclization were compared to those of corresponding semicarbazones. The kinetic data were analyzed by means of the Hammett's equation and ρ values discussed.
All-organic device with integrated chemical filter dedicated to the selective measurement of NO2 in air
2010
Abstract An original organic semiconductor gas sensor devoted to the selective monitoring of nitrogen dioxide in air has been successfully developed. This device combines the great sensitivity and the partial selectivity toward oxidizing gases of a molecular organic semiconductor, copper phthalocyanine, with the O3 filtering selectivity of an organic material, indigo. Experimental measurements highlight filtering yield of indigo close to 100% toward O3 and lower than 10% for NO2. Nanometric indigo layers were realized for the first time by thermal evaporation and characterized by FT-IR spectroscopy. Such all-organic device exhibits a high NO2 sensitivity for low concentrations, a resolution…
A hybrid catalyst for decontamination of organic pollutants based on a bifunctional dicopper(II) complex anchored over niobium oxyhydroxide
2017
Abstract This article describes the preparation and characterization of a hybrid oxidation catalyst for decontamination of organic pollutants which involves a bifunctional dicopper(II) complex and the niobium(V) oxyhydroxide as the active species, the later one being also a solid support. The pH range for the existence of the active species was determined by potentiometric and UV–vis spectroscopy at 25 °C and 0.15 M NaCl in a H 2 O/EtOH (70:30 v/v) solvent mixture containing copper(II) and the ligand N , N -2,2′-ethylenediphenylenebis(oxamic acid) (H 4 L). As far as the hybrid material is concerned, FTIR, FT-Raman, TEM and SEM images, surface area and TG/DTA analyses showed the occurrence o…
Combined CO/CH4 oxidation tests over Pd/Co3O4 monolitic catalyst: effects of high reaction temperature and SO2 exposure on the deactivation process
2007
Abstract CO and CH 4 combined oxidation tests were performed over a Pd (70 g/ft 3 )/Co 3 O 4 monolithic catalyst in conditions of GHSV = 100,000 h −1 and feed composition close to that of emission from bi-fuel vehicles. The effect of SO 2 (5 ppm) on CO and CH 4 oxidation activity under lean condition ( λ = 2) was investigated. The presence of sulphur strongly deactivated the catalyst towards methane oxidation, while the poisoning effect was less drastic in the oxidation of CO. Saturation of the Pd/Co 3 O 4 catalytic sites via chemisorbed SO 3 and/or sulphates occurred upon exposure to SO 2 . A treatment of regeneration to remove sulphate species was attempted by performing a heating/coolin…
Diffusion of Oxygen in Thermally Grown Oxide Scales
2009
High temperature reactivity of materials under oxidizing atmospheres is based on the formation of protective oxide scales. The protectiveness is obtained when the thermally grown oxide scales are dense, continuous and adherent to the metallic substrates (even during thermal shocks); as a matter of fact, the growth of the scale has to be governed by diffusion of species across the growing scale. The diffusing species are coming from the substrate (metallic ions) and/or from the oxidizing atmosphere (oxygen ions). The understanding of growth mechanisms can be reached by making two stage oxidation experiments, using oxygen isotopes. The experiment consists in oxidizing first the metallic subst…
Rapid Catalytic Water Disinfection from Earth Abundant Ca 2 Fe 2 O 5 Brownmillerite
2021
Water disinfection is a crucial challenge for humanity. Approaches that are effective, cheap, environmentally friendly, and do not promote gene exchange between bacteria are urgently required. Strongly oxidizing radicals are highly promising to achieve this as they lead to bacterial activation at high efficiencies. However, sources to consistently generate these radicals are limited to high energy UV/H2O2 treatments requiring a large energy input. Here the use of abundant, cheap, brownmillerite (Ca2Fe2O5) is demonstrated as an efficient radical generation material under dark conditions, showing a seven order of magnitude decrease in bacterial concentration over 10 min. This decrease is attr…
Eh and pH gradients in Camembert cheese during ripening: Measurements using microelectrodes and correlations with texture
2007
International audience; This study investigated the use of microelectrodes to continuously and simultaneously monitor pH and redox potential (Eh) gradients in Camembert cheeses from the rind to the core, as a function of ripening time (15 and 35 days). Cheeses were shown to be heterogeneous throughout their mass. An Eh gradient existed from the rind to the core. The surface was oxidizing (+330 to +360 mV) and the core was reducing and became more so in the course of ripening (−300 to −360 mV). A relationship between firmness and Eh was shown. pH gradients were in line with those previously described in the literature and related to ammonium and lactate gradients. Gradients evolved from the …
Protonation and oxidation chemistry of a pentaethylcyclopentadienyl-containing molybdenum(IV) trihydride complex
2000
International audience; Compound CpEtMoCl4 (CpEt=η5-C5Et5) (1) can be transformed into CpEtMoH3(dppe) (2) and CpEtMoD3(dppe) (2-d3) [dppe=1,2-(diphenylphosphino)ethane] by reaction with LiAlX4 (X=H and D, respectively). The protonation and oxidation studies of these two compounds, in comparison with previously reported studies on (C5Me5) analogs, show important differences that may be attributed to a kinetic stabilization of the products, which is steric in nature. Protonation of 2 with HBF4 in acetonitrile affords [CpEtMoH4(dppe)]+ (3), which only slowly decomposes to [CpEtMoH2(MeCN)(dppe)]+ (4). Further protonation of the latter affords the monohydride species [Cp*MoH(dppe)(MeCN)2]2+ in t…
Simulation of abrasion–corrosion at high temperatures by in situ pulsed laser spallation of oxide films
1999
Abstract A pulsed Nd:YAG laser combined with a thermogravimetric cell has been used to spall in situ the oxide films grown on a Fe–2.25Cr–1Mo steel at high temperature in oxidizing media. This technique allows to define the oxidation rate of bare metal surfaces, which can be used to simulate the corrosion-dominated regime during slurry–erosion tests.