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Solvent Medium (solvent + medium)
Selected AbstractsCopper-Catalyzed N-Arylation of Amines/Amides in Poly(ethylene glycol) as Recyclable Solvent Medium.CHEMINFORM, Issue 28 2006Srivari Chandrasekhar 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, Structure and a DFT/TDDFT Study of a Diimido-Bridged Asymmetric Dimolybdenum Complex,EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 34 2007Kuntal Pal Abstract The homobimetallic complex (Bu4N)2[MoO(mnt)Mo{o -aminobenzothiolato(3,)- N,S}2(mnt)] (2; mnt = 1,2-dicyanoethylenedithiolate) has been synthesized as a dark green solid by treating (Bu4N)2[Mo2O4(mnt)2] (1) with o -aminothiophenol in CH3CN. An X-ray crystal structure analysis of 2 reveals that it possesses an asymmetric structure where one Mo has a distorted octahedral geometry and the other a square-pyramidal geometry. The basal plane of the two Mo centers makes an angle of 26.41°, which is nearly one quarter of 90°. The shape of the ,(Mo=O) band in the IR spectrum of 2 suggests that these Mo atoms may have different oxidation states. The different reactivity of 1 with o -aminothiophenol and 2-aminoethanethiol was followed by EPR spectroscopy, and analysis of the different end-products from these reactions supports the proposal that 2 is a mixed-valence compound containing MoVI and MoIV centers. The electronic structures of 1 and 2 have been calculated at the DFT level of theory to analyse the effect of a deviation of the basal plane on the metal,metal bond in 2. The cyclic voltammetric responses of 1 and 2 have been measured to correlate the data with the computational results. TDDFT calculations have been performed on 1 and 2 in the gas phase and also in a solvent medium to assign the transitions corresponding to the peaks found in the respective experimental electronic absorption spectra of these complexes.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Cyclic Enones as Substrates in the Morita,Baylis,Hillman Reaction: Surfactant Interactions, Scope and Scalability with an Emphasis on FormaldehydeADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 7-8 2009Brett Abstract Traditionally, cyclic enones and formalin are reactants notorious for displaying problematic behaviour (i.e., poor solubility and low yields) under Morita,Baylis,Hillman (MBH) reaction conditions. The body of research presented herein focuses on the use of surfactants in water as a solvent medium that offers a resolution to many of the issues associated with the MBH reaction. Reaction scope, scalability and small angle X-ray scattering have been studied to assist with the understanding of the reaction mechanism and industrial application. A comparison against known literature methods for reaction scale-up is also discussed. [source] Trifluoromethanesulfonic acid, an alternative solvent medium for the direct electrophilic fluorination of DOPA: new syntheses of 6-[18F]fluoro- L -DOPA and 6-[18F]fluoro- D -DOPAJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 14 2007Babak Behnam Azad Abstract Previous work from this laboratory has shown that the direct fluorination of 3, 4-dihydroxy-phenyl- L -alanine (L -DOPA) in anhydrous HF (aHF) or BF3/HF with F2 is an efficient method for the synthesis of 6-fluoro- L -DOPA. Since then, 18F-labeled 6-fluoro- L -DOPA ([18F]6-fluoro- L -DOPA) has been used to study presynaptic dopaminergic function in the human brain and to monitor gastrointestinal carcinoid tumors. This work demonstrates that the reactivity and selectivity of F2 toward L -DOPA in CF3SO3H is comparable with that in aHF. This new synthetic procedure has led to the production of [18F]fluoro- L -DOPA and [18F]fluoro-D-DOPA isomers in 17±2% radiochemical yields (decay corrected with respect to [18F]F2). The 2- and 6-FDOPA isomers were separated by HPLC and subsequently characterized by 19F NMR spectroscopy. The corresponding [18F]-FDOPA enantiomers have been obtained in clinically useful quantities by a synthetic approach that avoids the use of aHF. Copyright © 2007 John Wiley & Sons, Ltd. [source] Synthesis and properties of silica/polystyrene/polyaniline conductive composite particlesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 2 2005Chia-Fen Lee Abstract In this study, silica/polystyrene/polyaniline (SiO2/PS/PANI) conductive composite particles were synthesized by four sequential reactions. The nanosized SiO2 particles were synthesized from tetraethoxysilane (TEOS) by a sol,gel process with water as the solvent medium, followed by a surface modification with triethoxyvinylsilane; then the surface modified SiO2 particles were used as seeds to synthesize SiO2/PS composite particles with soapless seeded emulsion polymerization. Finally, the SiO2/PS particles were used as seeds to synthesize the SiO2/PS/PANI conductive composite particles. The sol,gel process of SiO2, the effect of surface modification, and several other factors that influenced polymerization of styrene in the soapless seeded emulsion polymerization will be discussed. Either potassium persulfate (KPS) or 2,2,-azobis(isobutyramidine) dihydrochloride (AIBA) was used as the initiator to synthesize the uniform SiO2/PS particles successfully, and the cross-section morphology of the SiO2/PS particles was found to be of a core,shell structure, with SiO2 as the core, and PS as the shell. The SiO2/PS particles were well dispersed in many organic solvents. In the following step to synthesize SiO2/PS/PANI conductive composite particles, sodium dodecyl sulfate (SDS) played an important role, specifically, to absorb aniline onto the surfaces of the SiO2/PS particles to carry out the polymerization of aniline over the entire surface of the particles. The conductivity of the SiO2/PS/PANI composite particles approached that of semiconductive materials. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 342,354, 2005 [source] Preparation and Characterisation of Pd Nanoclusters in Hyperbranched Aramid Templates to be used in Homogeneous CatalysisMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 12 2003Daniela Tabuani Abstract In the present paper the potential use of hyperbranched (HB) aramids as metallic solution stabilisers and carriers for homogeneous catalysis is outlined. Aramids, synthesised either from A2,+,B3 reagents [namely, p -phenylenediamine (PPD) and trimesic acid (TMA)] or from an AB2 monomer [i.e., 5-(4-aminobenzamido)isophtalic acid, named ABZAIA], have been used to stabilise palladium nanoclusters dispersed in two solvent media, namely N,N, -dimethylformamide (DMF) and dimethyl sulfoxide (DMSO). The influence of the nature of the polymeric support as well as of the solvent medium on both cluster dimensions and stability of the solutions has been investigated. Indeed, the interactions between the polymeric support and the metallic precursor (PdCl2), as revealed by 1H NMR spectroscopy, involve only the amino groups of the HB aramids. Metal nanocluster dimensions and stability are strongly dependent on the polymer used as a stabilizer. Transmission electron microscopy (TEM) analysis has shown that the presence of HB polymer in the solution reduces cluster dimensions and allows the obtaining of stable systems. The low concentration of NH2 end groups in the poly(AB2) system leads to the formation of Pd particles of rather low dimensions with a high tendency to aggregate. All prepared solutions are stable under inert atmosphere for at least a month, with an improved stabilisation when using the poly(A2,+,B3) system for more than five months. A TEM micrograph of poly(ABZAIA)/Pd from a DMSO solution. [source] | |||||||||||||