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Subsequent Oxidation (subsequent + oxidation)
Selected AbstractsGram-Scale Synthesis of Cu2O Nanocubes and Subsequent Oxidation to CuO Hollow Nanostructures for Lithium-Ion Battery Anode MaterialsADVANCED MATERIALS, Issue 7 2009Ji Chan Park A procedure for gram-scale synthesis of monodisperse Cu2O nanocubes by a simple polyol process is demonstrated. The nanocubes are subsequently oxidized to form CuO hollow cubes, spheres, and urchin-like particles, through a sequential dissolution,precipitation process. The CuO urchin-like particles exhibited excellent electrochemical performance and stability, superior to those of hollow structures, for lithium-ion battery anode materials. [source] Ferromagnetism in ZnO Nanowires Derived from Electro-deposition on AAO Template and Subsequent Oxidation,ADVANCED MATERIALS, Issue 6 2008J. B. Yi ZnO wires are prepared from the oxidation of Zn wires, which are electrodeposited into AAO template. The ZnO wires show ferromagnetism at room temperature. A detailed study indicates that, owing to incomplete oxidation, Zn clusters embedded in the ZnO matrix may attribute to the room-temperature ferromagnetism. [source] Synthesis of Some Trifluoromethylated Cyclodextrin Derivatives and Analysis of Their Properties as Artificial Glycosidases and OxidasesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 4 2007Jeannette Bjerre Abstract Cyclodextrin derivatives containing trifluoromethyl groups at C6 of the A and D rings were synthesized for the purpose of creating artificial enzymes. The compounds were synthesized by perbenzylation of ,-cyclodextrin followed by selective A,D-debenzylation according to Sina˙. Subsequent oxidation to dialdehyde with Dess,Martin periodinane followed by addition of CF3 by using Arduengo carbene and TMSCF3 led to the C6 -bistrifluoromethylated alcohols. These were either deprotected by hydrogenolysis or subjected to another round of oxidation to provide the corresponding ketones that were deprotected. The trifluoromethylated alcohols were found to be weak artificial enzymes catalysing hydrolysis of nitrophenyl glycosides at neutral pH with a kcat/kuncat of up to 56. It is proposed that this catalysis is analogues to the catalysis performed by related cyanohydrins. The trifluoro ketones were likewise weak articial enzymes catalysing oxidation of amines to nitro derivatives or alcohols to ketones with a kcat/kuncat of up to 133. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Preparation of N -Glycosylhydroxylamines and Their Oxidation to Nitrones for the Enantioselective Synthesis of IsoxazolidinesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 21 2003Stefano Cicchi Abstract N -benzyl- and N -methyl- N -glycosylhydroxylamines 3a,i were conveniently obtained by reaction of sugars with N -substituted hydroxylamines according to a novel procedure. Subsequent oxidation occurred at the alkyl group, selectively affording the corresponding C -phenyl- and C -unsubstituted N -glycosylnitrones. C -phenyl- N -glycosylnitrones 10 and 13 underwent highly stereoselective 1,3-dipolar cycloaddition with dimethyl maleate, with the sugar moiety acting as a chiral auxiliary. Final removal of the glycosyl moiety afforded enantiopure enantiomeric isoxazolidines 17 and ent -17 which are oxa-analogues of proline diester derivatives. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] Migration of mercury from dental amalgam through human teethJOURNAL OF SYNCHROTRON RADIATION, Issue 2 2008Hugh H. Harris Exposure to mercury from dental amalgams, with possible negative health effects, has generally been considered to occur via either erosion or evaporation directly from the surface of fillings, followed by ingestion. The aim of this study was to determine the relative importance of the direct migration of mercury through the tooth as an alternative exposure pathway. X-ray fluorescence imaging has been used to determine quantitatively the spatial distribution of Hg, Ca, Zn and Cu in sections of human teeth that had been filled with amalgam for more than 20 years. X-ray absorption near-edge spectroscopy (XANES) was also employed to gain chemical information on the mercury present in the teeth. Hg (up to ,10,mg,g,1) and Zn (>100,mg,g,1) were detected in the teeth several millimetres from the location of the amalgams. At high resolution, Hg showed higher concentrations in dentinal tubules while Zn was generally evenly distributed. XANES showed that the chemical form of Hg that had migrated into the tooth had been altered from that present in the amalgam. The differing spatial distributions of Hg and Zn suggest distinct transport mechanisms for the two metals, presumably chemical for Zn and initially physical for Hg. Subsequent oxidation of Hg may lead to a loss of mobility or the development of a secondary transport mechanism. Most importantly the detection of Hg in areas of the tooth that once contained an active bloodstream and in calculus indicates that both exposure pathways should be considered as significant. [source] Dose-dependent stimulation of hepatic retinoic acid hydroxylation/oxidation and glucuronidation in brook trout, Salvelinus fontinalis, after exposure to 3,3,,4,4,-tetrachlorobiphenylENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 3 2000Patrick M. Boyer Abstract Extremely low stores of vitamin A have been reported in fish and birds inhabiting regions contaminated by coplanar polychlorinated biphenyls (PCBs) and other organochlorines, suggesting many possible effects on retinoid biochemical pathways. Metabolic imbalances associated with biologically active retinoids (e.g., retinoic acid) could be associated with teratogenesis, edema, growth inhibition, reproductive impairment, immunosuppression, and susceptibility to cancer. Sexually mature brook trout were injected intraperitoneally with the coplanar PCB 3,3,,4,4,-tetrachlorobiphenyl (TCBP) and again 4 weeks later. At 8 weeks, retinoic acid metabolism was measured in liver microsomes. To our knowledge, retinoic acid conjugation by UDP-glucuronyltransferase is described here for the first time in fish. A substantial rate of glucuronidation was detected in the microsomes from control brook trout, which tended to increase over the dose range of TCBP. Glucuronidation was significantly greater in fish receiving the 10 ,g/g body weight dose level. Metabolism through the cytochrome P450 system was also dose-dependent, resulting in significantly greater production of 4-hydroxyretinoic acid at the 10 ,g/g dose level. In contrast, subsequent oxidation to 4- oxo -retinoic acid was greatest at the 1 ,g/g dose level and did not increase further at higher doses. Liver stores of dehydroretinyl palmitate/oleate were significantly decreased at the 5 and 10 ,g/g dose levels. [source] Generation of Monodisperse Inorganic,Organic Janus Microspheres in a Microfluidic DeviceADVANCED FUNCTIONAL MATERIALS, Issue 10 2009Naveen Prasad Abstract This study presents a simple synthetic approach for the in situ preparation of monodisperse hybrid Janus microspheres (HJM) having organic and inorganic parts in a PDMS-based microfluidic device. Based on the mechanism of shear-force-driven break-off, merged droplets of two photocurable oligomer solutions having distinctive properties are generated into an immiscible continuous phase. Functionalized perfluoropolyether (PFPE) as the organic phase and hydrolytic allylhydridopolycarbosilane (AHPCS) as the inorganic phase are used for the generation in aqueous medium of HJM with well-defined morphology and high monodispersity (average diameter of 162,µm and a 3.5% coefficient of variation). The size and shape of the HJM is controlled by varying the flow rate of the disperse and continuous phases. The HJM have two distinctive regions: a hydrophobic hemisphere (PFPE) having a smooth surface and a relatively hydrophilic region (AHPCS) with a rough, porous surface. In addition, pyrolysis and subsequent oxidation of these HJM convert them into SiC-based ceramic hemispheres through the removal of the organic portion and etching off the silica shell. The selective incorporation of magnetic nanoparticles into the inorganic part shows the feasibility of the forced assembly of HJM in an applied magnetic field. [source] Formal Synthesis of Olivacine via IndolylborateHELVETICA CHIMICA ACTA, Issue 10 2008Minoru Ishikura Abstract Palladium-catalyzed tandem cyclization,cross-coupling reaction of indolylborate 2 and vinyl bromide 5 was successfully applied in a short formal synthesis of olivacine. The reaction of 2 with 5 in the presence of Pd(OAc)2 readily afforded three kinds of products, triene derivative 6 and vinylindole derivative 7, along with a small amount of the piperidine derivative 8 (Scheme,2). On the other hand, the reactions of 2 with bromide 10 or 15 were also examined (Schemes,4 and 5), and their outcome markedly depended on the relative ease of ring closure as a function of ring size. Irradiation of 6 with a high-pressure mercury lamp (,9; Scheme,2), followed by removal of the N -[(benzyloxy)carbonyl] group and subsequent oxidation afforded, after deprotection, pyridocarbazole 23, and the conversion of 23 to olivacine is known (Scheme,6). [source] Fungal tyrosinases: new prospects in molecular characteristics, bioengineering and biotechnological applicationsJOURNAL OF APPLIED MICROBIOLOGY, Issue 2 2006S. Halaouli Abstract Tyrosinases are type-3 copper proteins involved in the initial step of melanin synthesis. These enzymes catalyse both the o -hydroxylation of monophenols and the subsequent oxidation of the resulting o -diphenols into reactive o -quinones, which evolve spontaneously to produce intermediates, which associate in dark brown pigments. In fungi, tyrosinases are generally associated with the formation and stability of spores, in defence and virulence mechanisms, and in browning and pigmentation. First characterized from the edible mushroom Agaricus bisporus because of undesirable enzymatic browning problems during postharvest storage, tyrosinases were found, more recently, in several other fungi with relevant insights into molecular and genetic characteristics and into reaction mechanisms, highlighting their very promising properties for biotechnological applications. The limit of these applications remains in the fact that native fungal tyrosinases are generally intracellular and produced in low quantity. This review compiles the recent data on biochemical and molecular properties of fungal tyrosinases, underlining their importance in the biotechnological use of these enzymes. Next, their most promising applications in food, pharmaceutical and environmental fields are presented and the bioengineering approaches used for the development of tyrosinase-overproducing fungal strains are discussed. [source] Synthesis of liquid crystalline,amorphous block copolymers by the combination of atom transfer and promoted cationic polymerizationJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2007S. Demirhan Abstract Block copolymers of liquid crystalline 6-(4-cyanobiphenyl-4,-oxy) hexyl acrylate (LC6) and cyclohexene oxide (CHO) were obtained by the combination of atom transfer radical polymerization (ATRP) and promoted cationic polymerization (PCP). In the first part, a bifunctional initiator containing benzoin and halide groups in the same structure was used as an initiator in ATRP of LC6, in diphenyl ether in conjunction with CuBr/N,N,N,,N,,N,-pentamethyldiethylenetriamine as a catalyst. The obtained photoactive liquid crystalline polymers poly[6-(4-cyanobiphenyl-4,-oxy)hexyl acrylate] (PLC6), were used to induce polymerization of CHO through formation of electron donor polymeric radicals upon photolysis and subsequent oxidation to corresponding carbocations in the presence of onium salt. The spectral, thermal and optical measurements confirmed a full combination of ATRP and PCP, which resulted in the formation of AB-type block copolymers. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 [source] Synthesis of a linear polyethylene macromonomer and preparation of polystyrene- graft -polyethylene copolymers via grafting-through atom transfer radical polymerization,JOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2007Hiromu Kaneyoshi Abstract A vinyl-terminated linear polyethylene (number-average molecular weight = 1800, weight-average molecular weight/number-average molecular weight = 1.7, functionality = 92%) prepared by ethylene coordination polymerization was transformed into a monohydroxy-terminated linear polyethylene by hydroalumination of the vinyl group with diisobutylaluminum hydride and subsequent oxidation and hydrolysis. This monohydroxy-terminated linear polyethylene was quantitatively converted into a linear polyethylene macromonomer with a terminal ,-methacrylate group through esterification followed by dehydrobromination. A grafting-through atom transfer radical polymerization of the ,-methacrylate-terminated polyethylene and styrene was performed to yield a well-defined polystyrene- graft -polyethylene copolymer. The number-average molecular weight of the graft copolymers, measured by gel permeation chromatography, was lower than the predetermined number-average molecular weight, presumably because of the intramolecular aggregation of polyethylene side chains. The ,-methacrylate-terminated polyethylene content and number-average molecular weight of polystyrene- graft -polyethylene were determined by 1H-NMR. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 105: 3,13, 2007 [source] A convenient one-pot procedure for the synthesis of 2-aryl quinazolines using active MnO2 as oxidantJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 5 2010Yi-Yuan Peng A variety of 2-aryl quinazolines were synthesized from the condensation of 2-aminobenzylamines and aryl aldehydes to form 2-aryl-1,2,3,4-tetrahydroquinazolines and subsequent oxidation of the intermediates with MnO2. J. Heterocyclic Chem., (2010). [source] Metastable alumina formation during oxidation of FeCrAl and its suppression by surface treatmentsMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 12 2005E. N'Dah Abstract The influence of various surface treatments of industrial FeCrAl grades was investigated in order to reduce the formation of transition aluminas during thermal oxidation in the 800,950°C temperature range. High temperature gas phase annealing in H2 -H2O mixtures promoted the initial formation of an alpha thin film and no transition alumina formed during subsequent oxidation at lower temperatures, showing very low weight gains compared to non-treated grades. Such a treatment was shown to be efficient for isothermal oxidation in oxygen of laboratory foil specimens but also for cyclic air exposure of fiber mats in near-real operating conditions. Surface modification by application of a slurry TiO2 coating before oxidation was also shown to greatly reduce the amount of transition alumina, observed by X-Ray Diffraction and Laser Induced Optical Spectroscopy. For both treatments, the optimal conditions were determined and the influence on oxidation rate was assessed. [source] ChemInform Abstract: One-Pot Conversion of Aromatic Bromides and Aromatics into Aromatic Nitriles.CHEMINFORM, Issue 43 2010Sousuke Ushijima Abstract Various bromoarenes and p-iodotoluene can be efficiently converted to nitriles through a one-pot sequence including lithiation, reaction with DMF and subsequent oxidation with iodine in the presence of ammonia. [source] | ||||||||||||||||