Search results for "OXIDATION"
showing 10 items of 1913 documents
Dioxomolybdenum(VI) complexes of hydrazone phenolate ligands - syntheses and activities in catalytic oxidation reactions
2021
Abstract The new cis-dioxomolybdenum (VI) complexes [MoO2(L2)(H2O)] (2) and [MoO2(L3)(H2O)] (3) containing the tridentate hydrazone-based ligands (H2L2 = N'-(3,5-di-tert-butyl-2-hydroxybenzylidene)-4-methylbenzohydrazide and H2L3 = N'-(2-hydroxybenzylidene)-2-(hydroxyimino)propanehydrazide) have been synthesized and characterized via IR, 1H and 13C NMR spectroscopy, mass spectrometry, and single crystal X-ray diffraction analysis. The catalytic activities of complexes 2 and 3, and the analogous known complex [MoO2(L1)(H2O)] (1) (H2L1 = N'-(2-hydroxybenzylidene)-4-methylbenzohydrazide) have been evaluated for various oxidation reactions, viz. oxygen atom transfer from dimethyl sulfoxide to t…
Exceedingly Fast Oxygen Atom Transfer to Olefins via a Catalytically Competent Nonheme Iron Species
2016
El mateix article està publicat en alemany a l'edició alemanya d' 'Angewandte Chemie' (ISSN 0044-8249, EISSN 1521-3757), 2016, vol. 128, núm. 21, p.6418–6422. DOI http://dx.doi.org/10.1002/ange.201601396 The reaction of [Fe(CF3SO3)2(PyNMe3)] with excess peracetic acid at −40 °C leads to the accumulation of a metastable compound that exists as a pair of electromeric species, [FeIII(OOAc)(PyNMe3)]2+ and [FeV(O)(OAc)(PyNMe3)]2+, in fast equilibrium. Stopped-flow UV/Vis analysis confirmed that oxygen atom transfer (OAT) from these electromeric species to olefinic substrates is exceedingly fast, forming epoxides with stereoretention. The impact of the electronic and steric properties of the subs…
Methane-derived carbonate conduits from the late Aptian of Salinac (Marne Bleues, Vocontian Basin, France): Petrology and biosignatures
2015
Abstract Peculiar carbonate bodies occur in distinct marl layers of the Marnes Bleues Formation (Aptian–Albian, Vocontian Basin, Southern France). The carbonate conduits exhibit pipe- or sausage-like forms and a central channel. Their sizes range between 30 and 60 cm in length and 5–10 cm in diameter. The conduit carbonates consist of automicrite authigenically formed within the sediment. Millimeter-sized aggregates of framboidal pyrite are abundant within the conduit automicrites, probably representing former colonies of sulfate reducing bacteria. The central channel reflects former pathways of reduced fluids in the carbonate conduit. Ni-enrichments at the margins of the central cavity are…
Surface-immobilized DNAzyme-type biocatalysis
2014
The structure of the double helix of deoxyribonucleic acid (DNA, also called duplex-DNA) was elucidated sixty years ago by Watson, Crick, Wilkins and Franklin. Since then, DNA has continued to hold a fascination for researchers in diverse fields including medicine and nanobiotechnology. Nature has indeed excelled in diversifying the use of DNA: beyond its canonical role of repository of genetic information, DNA could also act as a nanofactory able to perform some complex catalytic tasks in an enzyme-mimicking manner. The catalytic capability of DNA was termed DNAzyme; in this context, a peculiar DNA structure, a quadruple helix also named quadruplex-DNA, has recently garnered considerable i…
Use of gases to improve survival of Bifidobacterium bifidum by modifying redox potential in fermented milk
2011
The aim of this work was to study the effect of the oxidoreduction potential, modified using gas, on the growth and survival of a probiotic strain, Bifidobacterium bifidum, and 2 yogurt strains, Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus. Three fermented milks were manufactured with an initial oxidoreduction potential value adjusted to +440 mV (control milk), +350 mV (milk gassed with N(2)), and -300 mV [milk gassed with N(2) plus 4% (vol/vol) H(2) (N(2)-H(2))]. Acidification profiles, growth during milk fermentation and survival during storage at 4 °C for 28 d were determined. This study showed that fermented probiotic dairy products made from milk gassed with…
Fine–grained spinel ferrites: From the reactivity to magnetic properties
1998
The oxidation at low temperature of fine-grained ferrites containing oxidizable cations such as Cu + , Fe 2+ , Mn 2+ , Mo 3+ , V 3+ , has led to new mixed-valent cation deficient ferrites with a large number of vacancies. It has been demonstrated by DTG analysis that each cation oxidizes at a specific temperature in close relation with the cation-oxygen distance. The kinetics oxidation of each oxidizable cation has been explained on the basis of a diffusion-induced stress effect when these stresses are generated by the chemical gradient induced during the oxidation process. When fine-grained ferrites contain some Co-cations, it has been revealed that the stresses have a significant influenc…
Cobalt in strontium titanate based perovskites: preparation, characterization and role in the photocatalytic propene partial oxidation
2016
Strontium titanate perovskite (SrTiO3) and analogous materials in which Y partially substitutes Sr have been prepared as basis to integrate Co in the structure. The Co inserrtion has been performed by wet impregnation or coprecipitation methods. The obtained powders have been physico-chemically characterized and tested as photocatalysts in the propene partial oxidation by using a solar simulating reactor. Correlation between photocatalytic performance and physicochemical characteristics of the different catalysts allows to assess a key role of local nanostructuring of CoOx sites on the selectivity and distribution of products.
A comparative study of the surface and bulk properties of lanthanum-strontium-manganese oxides La1âxSrxMnO3±δ as a function of Sr-content, oxygen…
1999
Abstract The properties of the perovskite-type La 1− x Sr x MnO 3± δ oxides (0≤ x ≤1) are related to the reversible redox reaction of manganese ions Mn 3+ ↔Mn 4+ . This reaction plays an essential role both in the interfacial transfers and transport properties and depends on relative cation concentrations and experimental conditions. In this paper we present experimental investigations aiming to determine, to compare and to control some of the surface and bulk properties of these oxides. The bulk and surface Mn 4+ contents were investigated by thermogravimetry analysis (TGA) in hydrogen and X-ray photo-electron spectroscopy (XPS) respectively. With a finely divided La 0.8 Sr 0.2 MnO 3 powde…
Synthesis and crystal structure of novel Ruddlesden–Popper strontium niobium oxynitrides
2002
Abstract The family (SrO)(SrNbO 2-x N) n is the first example of Ruddlesden-Popper strontium niobium oxynitrides and provides layered structures to obtain mixed valence niobium compounds with a variety of oxidation states and transport properties. We have prepared members with n =1 (Sr 2 NbO 3 N) and n =2 (Sr 3 Nb 2 O 5 N 2 ) by solid state reaction of Nb 2 O 5 and SrCO 3 at 900–1050 °C under ammonia flow. These compounds crystallize in the I4/mmm space group and show a range of anionic stoichiometry that together with the N/O ratio determines the formal oxidation state for niobium and therefore the resultant physical properties. Samples of the n =1 member show mixed valence Nb 5+ /Nb 4+ an…
GHB related acids are useful in routine casework of suspected GHB intoxication cases
2021
Abstract GHB related acids (3,4-dihydroxy butyric acid, 2,4-dihydroxy butyric acid and glycolic acid) are produced through oxidative GHB metabolism. These analytes could be potential biomarkers to ensure the diagnosis of a GHB intoxication and even prolong the detection window. Within this study, forensic routine cases were measured to consider the potential of additional gas chromatographic mass spectrometric analysis on these acids. 17 GHB positive real cases (10 serum samples and 7 urine samples) and 40 cases with suspicion of drugging in DFC cases and negative GHB results (21 serum samples and 19 urine samples) were evaluated. Increased GHB related acid concentrations were detected in a…