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Quantitative Conversion (quantitative + conversion)
Selected AbstractsSynthesis of polymeric 1-iminopyridinium ylides as photoreactive polymersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 4 2010Daniel Klinger Abstract Two synthetic routes to polymeric 1-imino pyridinium ylides as new photoreactive polymeric architectures were investigated. In the first approach, polymerization of newly synthesized 1-imino pyridinium ylide containing monomers yielding their polymeric analogues was achieved by free radical polymerization. Alternatively, reactive precursor polymers were synthesized and converted into the respective 1-imino pyridinium ylide polymers by polymer analogous reactions on reactive precursor polymers. Quantitative conversion of the reactive groups was achieved with pentafluorophenyl ester containing polymers and newly synthesized photoreactive amines as well as by the reaction of poly(4-vinylbenzoyl azide) with a photoreactive alcohol. The polymers obtained by both routes were examined regarding their photoreaction products and kinetics in solution as well as in thin polymer films. Contact angle measurements of water on the polymer films before and after irradiation showed dramatic changes in the hydrophilicity of the polymers. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 832,844, 2010 [source] Tetraalkylammonium-Free Heck Olefination of Deactivated Chloroarenes by Using a Macrocyclic Catalyst PrecursorCHEMISTRY - A EUROPEAN JOURNAL, Issue 8 2010Christoph Röhlich Dipl.-Chem. Palladium reservoir: A macrocyclic dinuclear Pd complex is applied to the Heck coupling of strongly deactivated aryl chlorides. The complex serves as a very stable precatalyst, which releases active Pd under normal reaction conditions (see scheme). The controlled release and recapture of active Pd provides sufficient stabilization to supersede the addition of tetrabutylammonium bromide. Quantitative conversions can be achieved under additive-free conditions. [source] Synthesis of Functionalized 1-Substituted Alkenylsilanols and Establishment of Conditions for Their Palladium-Catalyzed Cross-Coupling Reactions To Afford 1-Substituted Styrene DerivativesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 20 2004Sunil K. Ghosh Abstract An efficient method for the quantitative conversion of 1-substituted alkenyl(phenyl)silanes into the corresponding alkenylsilanols has been developed and used in their palladium(0)-catalyzed, tetrabutylammonium fluoride-promoted cross-coupling reaction with aryl iodides. Copper(I) chloride modulated the reactivity of TBAF in such a way that it virtually eliminated the protiodesilylation of alkenylsilanols, thus favoring the formation of ipso -coupled products. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Aerobic Oxidation of Benzylic Alcohols in Water by 2,2,6,6-Tetramethylpiperidine-1-oxyl (TEMPO)/Copper(II) 2- N -Arylpyrrolecarbaldimino ComplexesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 16 2009Abstract Novel copper(II) 2- N -arylpyrrolecarbaldimine-based catalysts for the aerobic oxidation of benzylic alcohols mediated by the 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) radical are reported. The catalytic activity for both synthesized and in situ made complexes in alkaline water solutions was studied revealing high efficiency and selectivity (according to GC selectivity always >99%) for both of these catalytic systems. For example, quantitative conversion of benzyl alcohol to benzaldehyde can be achieved with the in situ prepared bis[2- N -(4-fluorophenyl)-pyrrolylcarbaldimide]copper(II) catalysts in 2,h with atmospheric pressure of O2 at 80,°C. Interestingly, these catalysts can utilize dioxygen as well as air or hydrogen peroxide as the end oxidants, producing water as the only by-product. [source] Magnetic Nanoparticle Supported Second Generation Hoveyda,Grubbs Catalyst for Metathesis of Unsaturated Fatty Acid EstersADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 16 2009Zhu Yinghuai Abstract The Hoveyda,Grubbs catalyst has been successfully immobilized on surface-modified magnetic nanoparticles with a loading amount of 0.28,mmol ruthenium/g (magnetic support). The supported catalysts were active for the self-metathesis of methyl oleate and macro-monomer in a quantitative conversion, respectively. In addition, the catalyst can be easily separated by using a magnet and reused several times with sustained activity. [source] Fullerene-Promoted Singlet-Oxygen Photochemical Oxygenations in Glass-Polymer Microstructured ReactorsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 17 2008Tommaso Carofiglio Abstract In this paper we report the fabrication of thiolene-based microstructured reactors (MRs) that have been specifically designed to include solid-supported reagents within the microchannels network. We propose a convenient solution to realize reversible press-fit, leak-proof interconnects that greatly simplify the MR coupling to the external environment such as capillary tubing, sample reservoirs and pumps. The MRs have been used to carry out the oxidation of ,-terpinene and methionine using [60]fullerene, covalently linked to Tentagel® and silica gel matrices, as a singlet oxygen sensitizer. High conversions have been observed for both substrates although, in the case of ,-terpinene, a partial photodegradation of the endo -peroxide product was detected. Interestingly, in the case of methionine, a quantitative conversion to the corresponding sulfoxides was achieved in about 40 seconds, using low-power, white LED illumination. The reaction time is considerably shorter when compared to the batch procedure that requires, for the same process, about one hour illumination and the use of a 300-W tungsten halogen lamp. [source] Butanolysis of 2-methylbenzenediazonium ions: product distribution, rate constants of product formation, and activation parametersJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 5 2009M. José Pastoriza-Gallego Abstract We have determined the product distributions, the rate constants of product formation and substrate loss, and the activation parameters for the butanolysis of 2-methylbenzenediazonium, 2MBD, tetrafluoroborate in aqueous 1-Butanol (BuOH) solutions by combining UV,VIS spectroscopy, high performance liquid chromatography (HPLC), and a derivatization protocol that traps unreacted 2MBD as a stable azo dye. BuOH/H2O solutions are miscible over a narrow composition range, but in reverse micelles composed of sodium dodecyl sulfate, SDS, BuOH, and water, are miscible between 45,80%. Two major and two minor dediazoniation products are observed, 2-cresol, ArOH, 2-butyl-tolyl-ether, ArOBu, and small amounts of 2-chlorobenzene, ArCl (from HCl added to control solution acidity) and toluene, ArH (a reduction product). Product yields depend on experimental conditions, but quantitative conversion to products is achieved over the entire composition ranges investigated. The observed rate constants, kobs, obtained by monitoring 2MBD loss or by monitoring ArOH or ArOBu formation, are the same and they are only modestly affected by changes in the solution composition. The activation parameters obtained from the effect of temperature on kobs show that the enthalpy of activation is relatively high compared to those found in bimolecular reactions and the entropy of activation is small but positive. The results suggest that 2MBD is mainly sampling in the BuOH-H2O rich interfacial region of the reverse micelle and are consistent with 2MBD decomposing through a DN,+,AN mechanism, i.e., a rate limiting formation of an aryl cation that reacts immediately with nucleophiles. Copyright © 2008 John Wiley & Sons, Ltd. [source] Functional syndiotactic poly(,-hydroxyalkanoate)s via stereoselective ring-opening copolymerization of rac -,-butyrolactone and rac -allyl-,-butyrolactoneJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 12 2009Noureddine Ajellal Abstract The copolymerization of racemic ,-butyrolactone (rac -BLMe) with racemic "allyl-,-butyrolactone" (rac -BLallyl) in toluene, catalyzed by the discrete amino-alkoxy-bis(phenolate) yttrium-amido complex 1, gave new poly(,-hydroxyalkanoate)s with unsaturated side chains. The poly(BLMe - co -BLallyl) copolymers produced have a highly syndiotactic backbone structure (Pr = 0.80,0.84) with a random enchainment of monomer units, as evidenced by 13C NMR, and high molecular weight (Mn up to 58,000 g mol,1) with a narrow polydispersity (Mw/Mn = 1.07,1.37), as determined by GPC. The comonomer incorporation (5,50 mol % rac -BLallyl) was a linear function of the feed ratio. The pendant vinyl bond of the side-chains in those poly(BLMe - co -BLallyl) copolymers allowed the effective introduction of hydroxy or epoxy groups via dihydroxylation, hydroboration-oxidation or epoxidation reactions. NMR studies indicated that all of these transformations proceed in an essentially quantitative conversion and do not affect the macromolecular architecture. Some thermal properties (Tm, ,Hm, Tg) of the prepared polymers have been also evaluated. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3177,3189, 2009 [source] The influence of precursor's length and [diepoxide]o/[MPEG]o ratio on poly(ethylene glycol) star formation: The quantitative conversion of both precursorsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 21 2007Grzegorz Lapienis The analysis of the relation between Mn of MPEG and [diepoxide]o/[MPEG]o ratio allowed to determine the demarcation line for conditions giving either soluble stars: DGNG (,) and DGEG (,) or insoluble products: DGNG (,) and DGEG (,). Then conditions have been found for a quantitative conversion of both MPEG and diepoxides into stars. This was possible only for MPEG of Mn , 2000. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com.] [source] Synthesis and characterization of water-soluble barbiturate- and thiobarbiturate-functionalized polystyreneJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 6 2002S. Raja Abstract The synthesis and characterization of barbiturate- and thiobarbiturate-functionalized polystyrene from polystyrene homopolymer by polymer-modification reactions is discussed. Polystyrene homopolymer quantitatively functionalized at the para postion with diethyl oxomalonate functionality was subjected to a condensation reaction with urea and thiourea in the presence of sodium methoxide in methanol. This reaction proceeded essentially to quantitative conversion to the barbiturate- (BAPS) and thiobarbiturate-functionalized polystyrenes (TBAPS) as estimated by 1H NMR, UV, and IR spectroscopies. Thus, several copolymers of styrene with barbiturate- and thiobarbiturate-functionalized styrene were synthesized. The detailed characterizations of quantitatively functionalized polystyrene using gel permeation chromatographic, IR, UV, and 1H NMR spectroscopic techniques as well as thermogravimetric analysis are discussed. An application of the newly synthesized polymer in removing Cu(II) ions from aqueous solution is demonstrated. This is the first report on the synthesis of BAPS and TBAPS by the polymer-modification route or otherwise. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 731,737, 2002; DOI 10.1002/pola.10154 [source] Organotin catalysts grafted onto cross-linked polystyrene supports through polar spacersAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 2 2010Vanja Pinoie Abstract The present study investigates the suitability of a HypoGel support bearing oligomeric poly(ethylene glycol) (PEG) chains to act as an insoluble carrier for grafted organotin catalysts. Through the introduction of polar spacers, an improved swelling and site accessibility in the polar media typically involved in transesterification reactions are targeted. Advanced structural investigation shows that quantitative conversion into the targeted HypoGel-supported organotin trichloride is hampered by the existence of intra- and/or intermolecular donor-acceptor O,Sn interactions caused by the presence of donor moieties in the PEG-linker. Support is provided to the proposal that the latter interactions are at the origin of the moderate catalytic performance displayed by these HypoGel-supported catalysts, achieving only 41% conversion after 2 hours in the transesterification of ethyl acetate and n -octanol. In contrast with similar organotin catalysts supported by an alkyl spacer, the HypoGel-supported materials appear to be poorly recyclable and display poor leaching resistance. Copyright © 2009 John Wiley & Sons, Ltd. [source] Removal of pesticides from red and white wine by the use of fining and filter agentsAUSTRALIAN JOURNAL OF GRAPE AND WINE RESEARCH, Issue 1 2004GREG A. RUEDIGER Abstract Effects of the use of the fining and filtration agents, diatomaceous earth, bentonite, polyvinylpoly-pyrrolidone and activated carbon, on the removal of seven fungicides (carbendazim, chlorothalonil, fenarimol, metalaxyl, oxadixyl, procymidone and triadimenol) and three insecticides (carbaryl, chlorpyrifos and dicofol) from wines were investigated. Carbendazim was determined by high performance liquid chromatography (HPLC) after quantitative conversion into 2-aminobenzimidazole (2AB). The concentrations of all the other compounds in wine were quantified using a multi residue assay involving solid phase extraction (SPE) and gas chromatography-mass spectrometry (GC-MS). After treatment and processing, conducted under conditions simulating those that are typical in Australian commercial winemaking, the greatest reduction in concentration in all treatments was for chlorothalonil, chlorpyrifos and dicofol. There was a significant relationship between the extent of removal of each pesticide and its solubility in wine, such that the lower the solubility, the greater the extent of removal. Activated carbon had the largest effect on the removal of most pesticides, while bentonite had a major effect on the removal of carbendazim. For all compounds and agents, the rate of removal was greater in white wine than in red wine. [source] Pd on Porous Glass: A Versatile and Easily Recyclable Catalyst for Suzuki and Heck ReactionsCHEMSUSCHEM CHEMISTRY AND SUSTAINABILITY, ENERGY & MATERIALS, Issue 4 2008Christine Schmöger Abstract The catalytic activity of Pd supported on porous glass was studied for both Suzuki and Heck reactions under aerobic conditions, with particular focus on the Suzuki coupling. The reactions were carried out in water under microwave irradiation. The effects of the catalyst preparation process (calcination time and temperature), as well as the base, substrate, and boron compound used on the coupling reaction were investigated in relation to the reusability of the catalyst. Various bases promote the Suzuki coupling of phenylboronic acid with bromophenol very effectively resulting in quantitative conversion and excellent selectivity for the coupling product. However, most bases lead to deactivation of the catalyst after the first reaction cycle and the catalyst must be reactivated before reuse. Therefore, excellent conversions and selectivities for individual reactions are not sufficient to conclude if the chosen conditions are suitable for a given reaction, but results from recycling studies have to be considered also. [source] Imidazolium-2-Carboxylate as an Efficient, Expeditious and Eco-Friendly Organocatalyst for Glycerol Carbonate SynthesisADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-12 2009Prashant Abstract An improved and greener approach towards the synthesis of glycerol carbonate, via transesterification, using 1- n -butyl-3-methylimidazolium-2-carboxylate as catalyst is described. The catalyst loading as low as 1% was sufficient to yield quantitative conversions. A plausible mechanism is proposed for the catalytic cycle leading to product formation. [source] Cyclic poly(pyridine ether)s by the polycondensation of 2,6-difluoropyridine with various diphenolsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 20 2005Hans R. Kricheldorf Abstract The bistrimethylsilyl derivatives of six different diphenols were polycondensed with 2,6-difluoropyridine in N -methylpyrrolidone in the presence of K2CO3. On the basis of previous studies, the reaction conditions were optimized for almost quantitative conversions. The feed ratio was systematically varied to optimize the molecular weight. A 2 mol % excess of 2,6-difluoropyridine was needed to obtain maximum molecular weights. In the matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectra of the optimized polyethers, only cycles were found (detectable up to 5000 Da). Obviously, the relatively low molecular weights obtained under optimized conditions resulted from a limitation of the chain growth by cyclization, indicating a high cyclization tendency for poly(pyridine ether)s. The size exclusion chromatography measurements not only proved low molecular weights but also demonstrated the existence of bimodal mass distributions and high polydispersities. Protonation of the poly(pyridine ether)s required strong acids such as methane or trifluoromethane sulfonic acid. The solubilities of the neutral and protonated polyethers derived from bisphenol A were studied in various solvents. The MALDI-TOF mass spectra proved that protonation at 20,25 °C did not cause cleavage of ether bonds. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4781,4789, 2005 [source] Synthesis of Reactive Polymeric Dyes as Textile AuxiliariesMACROMOLECULAR MATERIALS & ENGINEERING, Issue 9 2003Angelina Altomare Abstract New polymeric materials containing amino-substituted azobenzene chromophores and reactive functional groups and characterized by some hydrophilicity were prepared with the aim of investigating alternative textile dyeing routes. The indicated materials were obtained either by copolymerization of suitable monomers or by modification of preformed polymers. In both cases commercial 4-amino-2,,3-dimethylazobenzene (FG) was used as chromogenic compound. According to the first synthetic strategy, the methacrylamido derivative of FG was copolymerized by free radical initiation with different monomers, such as methyl methacrylate, glycidyl methacrylate, N - tert -butylacrylamide, methacrylic acid, N -vinyl-2-pyrrolidinone, and vinyl acetate. Reaction of FG with preformed polymers containing epoxy groups generally afforded crosslinked materials. On the other hand, low FG loading extents were recorded by amidation of polymers containing carboxylic groups. Indeed, almost quantitative conversions were obtained only in the reaction of FG with anhydride containing polymers. The chemical structure, molecular weight properties, and the physical-chemical characteristics of all synthesized polymeric dyes were thoroughly investigated. Some very preliminary dyeing tests of different cloth types with the prepared polymeric dyes were also performed. UV absorption spectrum of poly(FGMAA) and poly(FGMAA- co -MMA) in chloroform at 25,°C (FGMAA,=,4-methacrylamido-2,,3-dimethylazobenzene). [source] | |||||||||||||