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Reaction Medium (reaction + medium)
Kinds of Reaction Medium Selected AbstractsN,N -Dimethylformamide as a Reaction Medium for Metal Nanoparticle SynthesisADVANCED FUNCTIONAL MATERIALS, Issue 5 2009Isabel Pastoriza-Santos Abstract The versatility of wet chemical methods has rendered them extremely popular for the preparation of metal nanoparticles with tailored size and shape. This Feature Article reviews the use of N,N -dimethylformamide (DMF) for the reduction of metal salts, mainly Au and Ag, while also acting as a solvent. Apart from describing the ability of DMF to reduce metal salts, the effect of different parameters, such as the concentration of capping agent and metal precursors, the presence of preformed seeds acting as catalysts or their crystalline structure, on particle morphology are analyzed. Published reports on the use of different capping agents are summarized, with particular emphasis on the role of poly(vinylpyrrolidone) to determine the morphology of the particles. Finally, a brief overview is provided on the modulation of the optical response in DMF-based metal nanoparticle colloids with tunable size and shape. [source] ChemInform Abstract: Poly(ethyleneglycol): A Versatile and Recyclable Reaction Medium in Gaining Access to Benzo[4,5]imidazo[1,2-a]pyrimidines under Microwave Heating.CHEMINFORM, Issue 49 2009Shu-Liang Wang Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 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. [source] ChemInform Abstract: PEG-400 as an Efficient Reaction Medium for the Synthesis of 2,4,5-Triaryl-1H-imidazoles and 1,2,4,5-Tetraaryl-1H-imidazoles.CHEMINFORM, Issue 25 2009Xi Cun Wang Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 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. [source] ChemInform Abstract: Friedel,Crafts Alkylation of Nitrogen Heterocycles Using [Bmim][OTf] as a Catalyst and Reaction Medium.CHEMINFORM, Issue 43 2008M. Lakshmi Kantam Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 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. [source] An Imidazolium-Based Phosphinite Ionic Liquid (IL-OPPh2) as a Reusable Reaction Medium and PdII Ligand in Heck Reactions of Aryl Halides with Styrene and n-Butyl Acrylate.CHEMINFORM, Issue 32 2007Nasser Iranpoor Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Regioselective [2 + 2]-Photocycloaddition Reactions of Chiral Tetronates , Influence of Temperature, Pressure, and Reaction Medium.CHEMINFORM, Issue 28 2007Martin Fleck Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Synthesis of 2,2,-Biimidazolium-Based Ionic Liquids: Use as a New Reaction Medium and Ligand for Palladium-Catalyzed Suzuki Cross-Coupling Reactions.CHEMINFORM, Issue 37 2005Ji-Chang Xiao Abstract For Abstract see ChemInform Abstract in Full Text. [source] Mizoroki,Heck Arylation of ,,,-Unsaturated Acids with a Hybrid Fluorous Ether, F-626: Facile Filtrative Separation of Products and Efficient Recycling of a Reaction Medium Containing a Catalyst.CHEMINFORM, Issue 12 2005Takahide Fukuyama Abstract For Abstract see ChemInform Abstract in Full Text. [source] Molten Salt as a Green Reaction Medium: Efficient and Chemoselective Dithioacetalization and Oxathioacetalization of Aldehydes Mediated by Molten Tetrabutylammonium Bromide.CHEMINFORM, Issue 38 2004Brindaban C. Ranu Abstract For Abstract see ChemInform Abstract in Full Text. [source] Osmium Tetroxide in Poly(ethylene glycol) (PEG): A Recyclable Reaction Medium for Rapid Asymmetric Dihydroxylation under Sharpless Conditions.CHEMINFORM, Issue 43 2003S. Chandrasekhar Abstract For Abstract see ChemInform Abstract in Full Text. [source] Catalytic Ethylene Polymerisation in Carbon Dioxide as a Reaction Medium with Soluble Nickel(II) CatalystsCHEMISTRY - A EUROPEAN JOURNAL, Issue 23 2006Amaia Bastero Dr. Abstract A series of neutral NiII,salicylaldiminato complexes substituted with perfluorooctyl- and trifluoromethyl groups, [Ni{,2 - N,O -6-C(H)NAr-2,4-R,2C6H2O}(Me)(pyridine)] (6,a: Ar=2,6-{4-(F17C8)C6H4}2C6H3, R,=I; 6,b: Ar=2,6-{4-(F3C)C6H4}2C6H3, R,=I; 6,c: Ar=2,6-{3,5-(F3C)2C6H3}2C6H3, R,=3,5-(F3C)2C6H3; 6,d: Ar=2,6-{4-(F17C8)C6H4}2C6H3, R,=3,5-(F3C)2C6H3; 6,e: Ar=2,6-{3,5-(F3C)2C6H3}2C6H3, R,=I) were studied as catalyst precursors for ethylene polymerisation in supercritical CO2. Catalyst precursors 6,a and 6,c, which are soluble in scCO2, afford the highest polymer yields, corresponding to 2×103 turnovers. Semicrystalline polyethylene (Mn typically 104 g,mol,1) is obtained with variable degrees of branching (11 to 24 branches per 1000 carbon atoms, predominantly Me branches) and crystallinities (54 to 21,%), depending on the substitution pattern of the catalyst. [source] Methyltrioxorhenium Catalysis in Nonconventional Solvents: A Great Catalyst in a Safe Reaction MediumCHEMSUSCHEM CHEMISTRY AND SUSTAINABILITY, ENERGY & MATERIALS, Issue 5 2010Marcello Crucianelli Dr. Abstract The requirement that chemical processes are sustainabable, reflected in waste reduction and the use of safe reagents and reaction conditions, is becoming even more stringent as a result of pressure by society and governments to preserve the environment and protect human health. Catalysis offers numerous benefits related to green chemistry, including lowered energetic reaction requirements; catalytic, rather than stoichiometric, amounts of materials; increased selectivity; lowered consumption of processing and separation agents; and, in many cases, the use of less-toxic compounds. Our research group has for a long time been studying methyltrioxorhenium in the oxyfunctionalization of different substrates, by using H2O2 or its urea-hydrogen peroxide complex as the primary oxidant. In this Review paper we aim to provide a full literature account on the catalytic activity and selectivity of methyltrioxorhenium in the oxyfunctionalization reaction, either in nonconventional solvents or under solvent-free conditions, with a particular emphasis on the use of ionic liquids as green reaction media. [source] Reaction kinetics for the degradation of phenol and chlorinated phenols using Fenton's reagentENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 1 2006Asim K. De Abstract Fenton's reaction is an advanced treatment technology often used for the removal of hazardous and refractory organic compounds from industrial wastewaters. It can effectively be used to degrade phenol and chlorophenols. The initial contaminant concentrations as well as the concentration of hydrogen peroxide and ferrous ions in aqueous solution have a significant effect on the effective degradation of contaminants. For a particular concentration of initial substrate in solution there should be an optimum level of ferrous ion concentration in the reaction medium. Based on experimental observations, a probable mechanism for Fenton's degradation kinetics has been proposed and a rate equation developed. From the rate expression, OH· radical reaction rate constants for the degradation of three compounds,phenol and o- and p-chlorophenols,in Fenton reaction were calculated to have values of 2.53 × 107, 2.38 × 107, and 2.45 × 107 m3 mol,1 s,1, respectively. © 2005 American Institute of Chemical Engineers Environ Prog, 2005 [source] Ultrasound-Assisted Synthesis of CuO Nanorods in a Neat Room-Temperature Ionic LiquidEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 19 2009Tarek Alammar Abstract CuO nanorods were prepared via ultrasound-assisted synthesis in the room temperature ionic liquid (RTIL) 1-butyl-3-methylimidazoliumbis(trifluoromethylsulfonyl)imide [C4mim][Tf2N] as a reaction medium. The structure and morphology of CuO nanorods were characterized with X-ray powder diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray analysis (EDX), X-ray photoelectron spectroscopy (XPS), vibrational and UV/Vis absorption spectroscopy. The synthesized CuO nanocrystals are of rod like shape with lengths from 30 to 100 nm and diameters of about 10 nm. Quantum size effects were observed as the bandgap of the CuO nanorods was determined to 2.41 eV from UV/Vis absorption measurements, which is significantly larger than the bulk value. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] High-Zirconium-Content Nano-Sized Bimodal Mesoporous SilicasEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 13 2006David Ortiz de Zárate Abstract Silica-based nanoparticulated bimodal mesoporous materials with high Zr content (43 , Si/Zr , 4) have been synthesized by a one-pot surfactant-assisted procedure from a hydroalcoholic medium using a cationic surfactant (CTMABr = cetyltrimethylammonium bromide) as structure-directing agent, and starting from molecular atrane complexes of Zr and Si as hydrolytic inorganic precursors. This preparative technique allows optimization of the dispersion of the Zr guest species in the silica walls. The bimodal mesoporous nature of the final high surface area nano-sized materials is confirmed by XRD, TEM, and N2 adsorption,desorption isotherms. The small intraparticle mesopore system (with pore sizes around 2,3 nm) is due to the supramolecular templating effect of the surfactant, while the large mesopores (around 12,24 nm) have their origin in the packing voids generated by aggregation of the primary nanometric mesoporous particles. The basicity of the reaction medium seems to be a key parameter in the definition of this last pore system. The effects induced by the progressive incorporation of Zr atoms on the mesostructure have been examined, and the local environment of the Zr sites in the framework has been investigated by UV/Vis spectroscopy. Observations based on the consequences of post-treatments of the as-synthesized materials with HCl/ethanol mixtures corroborate that the atrane method leads to Zr-rich materials showing enhanced site accessibility and high chemical homogeneity throughout the pore walls. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Borax-Catalyzed and pH-Controlled Selective Oxidation of Organic Sulfides by H2O2: An Environmentally Clean ProtocolEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 20 2009Sahid Hussain Abstract The selective oxidation of sulfides to sulfoxides and sulfones was achieved in high yields at room temperature with borax as a recyclable catalyst and H2O2 as the terminal oxidant by varying the pH of the reaction medium. The borax/H2O2 system can chemoselectively oxidize alkyl and aryl sulfides in the presence of oxidation-prone functional groups such as C=C, ,CN, and ,OH.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] 2H -Pyrrole Derivatives from an Aza-Nazarov Reaction Cascade Involving Indole as the Neutral Leaving GroupEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 21 2008Nugzar Ghavtadze Abstract Trifluoromethyl-substituted N -indolinyl-1-aza-1,4-dien-3-ones 4, which are accessible in good yields from indolinylimino esters 6 in a two-step procedure, undergo a novel type of aza-Nazarov cyclization if treated with strong acids to give the hitherto unknown 3-hydroxy-5H -pyrrole derivatives 8a,p. The solvent-free polyphosphoric acid/acyl anhydride system as the acidic reaction medium is especially efficient and requires only short reaction times. According to quantum chemical calculations the key step in the reaction cascade is the cleavage of the N,N bond of the hydrazone fragment of a protonated N -(indolin-1-yl)-1-aza-1,4-dien-3-one intermediate such as 10. This intermediate releases 3H -indole as an unusual, but very efficient neutral leaving group. Several 1-aza-1,4-dien-3-ones 4 and some 3-hydroxy-5H -pyrrole derivatives 8 were characterized by X-ray diffraction.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Conformationally Biased Selective Alkylation of trans -Cyclohexane-1,2-bis(sulfonamide) Assisted by Solvent-Tuned Protecting Groups: Applications to the Synthesis of a Large Optically Active Polyazamacrocycle,EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 17 2006Carmen Peña Abstract The selective alkylation of (R,R)-cyclohexane-1,2-bis(sulfonamide) with trityl bromoalkyl ethers has been studied in detail. The major formation of either mono- or dialkylated compounds clearly depends on the right combination of protecting groups and the reaction solvent. An exhaustive study suggests that this effect can be reasonably explained by the conformational preferences of the monoalkylated compounds, which also depend on the reaction medium, solvophobic effects and weak intramolecular interactions. Structural analysis by NOE measurements showed the presence of folded conformations in solution for all the tested examples. Monte Carlo conformational searches supported this proposal, showing a very good correlation between the fraction of folded species and the selectivity towards monoalkylation. Finally, tuning of the reaction conditions, leading to either extended or folded conformations of the monoalkylated synthetic intermediates, was exploited for the efficient synthesis of a large optically active polyazamacrocycle. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Pyrazole formation: Examination of kinetics, substituent effects, and mechanistic pathways,INTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 7 2008Joseph C. Sloop Reaction kinetics for the condensation of 1,3-diketones 1a,o with selected arylhydrazines (aryl = Ph, 4-NO2Ph, 4-CH3OPh, and 2,4-diNO2Ph) was studied using 19F NMR spectroscopy. Product regioselectivity is modulated by reactant ratios, substituents, and acidity. Reaction rates were found to be influenced by substituents on the diketones and on phenylhydrazines as well as by acidity of the reaction medium with rates varying as much as 1000-fold. Hammett , values for these cyclizations were determined. The reaction was found to be first order in both the diketone and arylhydrazine. The rate-determining step for pyrazole formation shifts as a function of pH. Mechanistic details and reaction pathways supporting these findings are proposed. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: 370,383, 2008 [source] Colorimetric investigation of the reaction between p -phenylendiamine and meta -substituted derivatives of benzene on a model supportINTERNATIONAL JOURNAL OF COSMETIC SCIENCE, Issue 3 2010M. Scalzo J. Cosmet. Sci., 60, 429,436 (July/August 2009) Synopsis The aim of this work was the employment of colorimetric techniques in the analysis of the color formed, on a proteic substrate, by the reaction between p -phenylendiamine and some meta -substituted benzene derivatives in the presence of hydrogen peroxide and in media at different pH values. In particular we investigated the chromatic variations that take place on the substrate in dependence on different reaction conditions. The obtained results show that for each couple of reagents the colorimetric data, namely the reflectance of the formed color, change considerably with the pH of the reaction medium and demonstrate how this parameter can be considered a good descriptor of the composition of the formed pigment. [source] A Tripodal Peptidic Titanium Phosphonate as a Homochiral Porous Solid Medium for the Heterogeneous Enantioselective Hydration of EpoxidesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 13 2010Anat Milo Abstract A porous, homochiral titanium-phosphonate material based on a tripodal peptide scaffold was used as a heterogeneous reaction medium for the enantioselective hydration (>99%) of styrene oxide. This titanium-phosphonate material, which was shown to contain confined chiral spaces, was prepared by polymerization of L -leucine onto a tris(2-aminoethyl)amine initiator, followed by capping with phosphonate groups and completed by non-aqueous condensation with titanium isopropoxide. Circular dichroism confirmed that the peptide tethers yielded a secondary structure. X-ray powder diffraction and transmission electron microscopy supported by a semi-empirical model showed the likely formation of a porous, lamellar material that was quantified by nitrogen adsorption. [source] Ionic Liquid (IL) as an Effective Medium for the Highly Efficient Hydroacylation Reaction of Aldehydes with AzodicarboxylatesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 6 2009Bukuo Ni Abstract The highly efficient hydroacylation reaction of aldehydes with azodicarboxylates has been carried out in the ionic liquid,1- n -butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, [BMIM] [NTf2]. The products were readily separated by extraction from the reaction medium and the ionic liquid could be recycled up to 8 times and the yields of the reactions were not affected. Compared to conventional solvents, high yields were achieved with aliphatic saturated aldehydes, and the reaction can be conducted under normal to mild conditions without the use of a catalyst. [source] Enantioselective Reduction of Diaryl Ketones Catalyzed by a Carbonyl Reductase from Sporobolomyces salmonicolor and its Mutant EnzymesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 4 2009Hongmei Li Abstract The carbonyl reductase from red yeast Sporobolomyces salmonicolor AKU4429 (SSCR) and its mutant enzymes effectively catalyzed the enantioselective reduction of diaryl ketones to give the corresponding chiral alcohols. Both conversion and enantioselectivity were dependent on the co-solvent in the reaction medium. Diaryl ketones with a para -substituent on one of the phenyl groups were reduced with high enantioselectivity (up to 99% ee), which is difficult to achieve using chemical methods such as chiral borane reduction, asymmetric hydrogenation or hydrosilylation. Mutation of SSCR at Q245 resulted in a higher amount of (S)-enantiomer in the products, and in the case of mutant Q245P with para -substituted diaryl ketones as substrate, this effect was so remarkable that the reduction enantiopreference was switched from (R) to (S). The present study provides valuable information about the catalytic properties of the carbonyl reductase SSCR toward the reduction of diaryl ketones, serving as basis for further engineering of this enzyme to develop efficient biocatalysts for highly enantiospecific reduction of diaryl ketones without high electronic dissymmetry or an ortho -substituent on one of the aryl groups. [source] Water in Stereoselective Organocatalytic ReactionsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1-2 2009Michelangelo Gruttadauria Abstract In this review, recent advances in asymmetric organocatalytic reactions carried out with variable amounts of water, from substoichiometric to a large excess (reaction medium), are discussed. We also summarize several proposed mechanisms for the different possibilities of the action of water both in the increased activity of the catalyst and in the asymmetric induction. Finally, the application of this catalytic methodology to the enantioselective synthesis of valuable compounds through enamine or iminium catalysis is presented. [source] New Simple Hydrophobic Proline Derivatives as Highly Active and Stereoselective Catalysts for the Direct Asymmetric Aldol Reaction in Aqueous MediumADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 17 2008Francesco Giacalone Abstract New 4-substituted acyloxyproline derivatives with different hydrophobic properties of the acyl group were easily synthesized and used as catalysts in the direct asymmetric aldol reaction between cyclic ketones (cyclohexanone and cyclopentanone) and several substituted benzaldehydes. Reactions were carried out using water, this being the best reaction medium examined. Screening of these catalysts showed that compounds bearing the most hydrophobic acyl chains [4-phenylbutanoate and 4-(pyren-1-yl)butanoate] provided better results. The latter catalysts were successfully used in only 2 mol% at room temperature without additives to give aldol products in excellent stereoselectivities. These results demonstrate that derivatization of the proline moiety with the proper simple hydrophobic substituent in the 4-position can furnish highly active and stereoselective catalysts without the need of additional chiral backbones in the molecule. Finally, an explanation of the observed stereoselectivities in the presence of water is provided. [source] Chemoselective Palladium-Catalyzed Reaction in Aqueous Media: Selectivity in the Reaction of Haloanilines with 1,1-Dimethylallyl AlcoholADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 4-5 2007Yuusaku Yokoyama Abstract Palladium-catalyzed reactions of various haloanilines with 1,1-dimethylallyl alcohol were carried out in the presence of a hydrophilic ligand, 3,3,,3,,-phosphinidyne tris(benzenesulfonic acid) trisodium salt (TPPTS), or a lipophilic phosphine ligand, 1,1,-bis(diphenylphosphino)ferrocene (DPPF). The reactions proceeded chemoselectively in aqueous solvent to give C -vinylated products under basic conditions or N -allylated products under neutral conditions in practical yields (up to 79,%). The use of an aqueous solvent played an important role in this chemoselectivity and allowed the development of a one-pot synthesis of 3-methylindole. This chemoselectivity is synthetically useful because the reactive position of haloanilines can be controlled simply by changing the basicity of the reaction medium, which eliminates the need to protect the amino group during the reaction. [source] 4-Aryl-2-quinolones through a Pseudo-Domino Heck/Buchwald,Hartwig Reaction in a Molten Tetrabutylammonium Acetate/ Tetrabutylammonium Bromide MixtureADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 3 2007Gianfranco Battistuzzi Abstract 4-Aryl-2-quinolones can be prepared from readily available o -bromocinnamamide and aryl iodides using phosphine-free palladium(II) acetate as the precatalyst and a molten tetra(n -butyl)ammonium acetate/tetra(n -butyl)ammonium bromide mixture as the reaction medium. The reaction proceeds through a pseudo-domino process involving two mechanistically independent, sequential catalytic cycles: a Heck reaction followed by an intramolecular Buchwald,Hartwig CN bond forming reaction. [source] One-Pot Conversion of Cephalosporin C to 7-Aminocephalosporanic Acid in the Absence of Hydrogen PeroxideADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 14 2005Fernando Lopez-Gallego Abstract The main drawback in the production of 7-aminocephalosporanic acid (7-ACA) at the industrial level is the inactivation of the enzymes implicated in the process due to the presence of hydrogen peroxide during the reaction. As an alternative, we have developed the conversion of cephalosporin C to 7-ACA in a single reactor without the presence of hydrogen peroxide during the reaction, achieving more than 80% yield. In order to develop this process, D -amino acid oxidase (DAAO) was co-immobilized with catalase (CAT), which is able to fully eliminate in situ the hydrogen peroxide formed by the neighbouring DAAO molecules. Thus, the product of the reaction is only ,-ketoadipyl-7-ACA. This system prevents the inactivation of the oxidase by hydrogen peroxide, solving the main problem of the enzymatic process. Moreover, we have found that ,-ketoadipyl-7-ACA is recognized as a substrate by glutaryl acylase (GAC) and hydrolyzed as long as glutaric acid is absent from the reaction medium (because it is able to inhibit the hydrolysis). The low stability of ,-ketoadipyl-7-ACA justifies the use of a single reactor, in which glutaryl acylase is already present when this substrate is generated. Thus, the whole process may (and must) be performed in a single step, and in the absence of hydrogen peroxide that could affect the stabilities of the involved enzymes. [source] A Mechanistic Study on Alcohol Oxidations with Oxygen Catalysed by TPAP-Doped Ormosils in Supercritical Carbon DioxideADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 6 2005Sandro Campestrini Abstract The heterogeneous oxidation of various alcohols with oxygen catalysed by TPAP-doped ormosils in scCO2 at 75,°C and 22.0,MPa has been studied in detail. Sol-gel segregation of TPAP into the inner porosity of an organically modified silica (ormosil) xerogel along with the use of a reaction medium which does not dissolve the catalyst, prevents aggregation of oxidation-inactive ruthenium derivatives without the need of chemical tethering. Thus, at least 140 TONs may be obtained in the oxidation of primary alcohols with the formation of aldehydes as sole reaction products. Investigation of the oxidation mechanism shows that the catalytic process exhibits a first-order dependence on the amount of catalyst, a fractional order on the alcohol concentration and a negative order for oxygen pressures higher than 0.2,bar. Evidence is presented for an associative oxidation mechanism simultaneously involving TPAP, organic substrate and oxygen. [source] Vesicles as reactors of nanoparticles: an anomalous small-angle X-ray scattering study of the domains rich in copper ionsJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 2007Attila Bóta The formation of copper hydroxide and copper oxide particles in the gaps among the stacks of multilamellar vesicles is described, illustrating a new pathway in the preparation of nanometre-scale particles. The in situ structural characterization of both the solid particles and the vesicles as a reaction medium was performed in the initial and final states of the process by using anomalous small-angle X-ray scattering (ASAXS) and freeze-fracture methods. The ASAXS method provides a description of the particle-size distribution of the copper nanoparticles, in spite of the fact that they are present in low concentration. This method allows the particle formation and growth to be monitored throughout the whole time range of the synthesis. [source] | ||||||||||||||||||||||||||||||||||