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Quaternary Ammonium Salts (quaternary + ammonium_salt)
Selected AbstractsChemInform Abstract: Enantioselective [1,2]-Stevens Rearrangement of Quaternary Ammonium Salts.CHEMINFORM, Issue 25 2008A Mechanistic Evaluation. 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] Asymmetric Phase-Transfer Catalysis of Homo- and Heterochiral Quaternary Ammonium Salts: Development and Application of Conformationally Flexible Chiral Phase-Transfer Catalysts.CHEMINFORM, Issue 10 2007Takashi Ooi 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] Highly Efficient Aza-Michael Reactions of Enones with Carbamates Using a Combination of Quaternary Ammonium Salts and BF3×OEt2 as a Catalyst.CHEMINFORM, Issue 15 2004Li-Wen Xu Abstract For Abstract see ChemInform Abstract in Full Text. [source] ChemInform Abstract: A Dramatic Improvement of Epoxide Selectivity of [Ti,Al]-, by Ion-Exchange with Quaternary Ammonium Salts.CHEMINFORM, Issue 2 2002Yasuhide Goa Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 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] ,N-Stereogenic Quaternary Ammonium Salts' from L -Amino Acids: Synthesis, Separation, and Absolute ConfigurationHELVETICA CHIMICA ACTA, Issue 4 2009Hua-Fang Wu Abstract Diastereoisomeric linear and cyclic ,N-chiral quaternary ammonium salts' (QASs) were efficiently synthesized from corresponding L -amino acids in high yields. The diastereoisomers of each pair of ,N-chiral QASs' were successfully separated. The absolute configurations of these QASs were determined predominately by X-ray single-crystal analysis. The 1H-NMR data of ,N-chiral QASs' provided characteristic information on the configuration of the N-chiral center. ,N-Chiral QASs' exemplified by [N(R)]- 2a and [N(S)]- 2a are stable in protic and aprotic solvents within a broad pH and temperature range. [source] Highly Enantioselective Synthesis of No-Carrier-Added 6-[18F]Fluoro- L -dopa by Chiral Phase-Transfer AlkylationEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 13 2004Christian Lemaire Abstract [18F]Fluoro- L -dopa, an important radiopharmaceutical for positron emission tomography (PET), has been synthesized using a phase-transfer alkylation reaction. A chiral quaternary ammonium salt derived from a Cinchona alkaloid served as phase-transfer catalyst for the enantioselective alkylation of a glycine derivative. The active methylene group of this Schiff-base substrate was deprotonated with cesium hydroxide and rapidly alkylated by the 2-[18F]fluoro-4,5-dimethoxybenzyl halide (X = Br, I). The reaction proceeded with high yield (> 90%) at 0 °C or room temperature in various solvents such as toluene or dichloromethane. Preparation of the [18F]alkylating agent on a solid support was developed. After labelling, the labeled [18F]fluoroveratraldehyde was trapped on a tC18 cartridge and then converted on the cartridge into the corresponding benzyl halide derivatives by addition of aqueous sodium borohydride and gaseous hydrobromic or -iodic acid. Hydrolysis and purification by preparative HPLC made 6-[18F]fluoro- L -dopa ready for human injection in a 25,30% decay-corrected radiochemical yield in a synthesis time of 100 min. The product was found to be chemically, radiochemically and enantiomerically pure (ee > 95%). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Kinetics of synthesis of bis-(benzoxazolyl-2-methyl) sulfide under phase-transfer catalysis conditionsINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 5 2009Zuo-Xiang Zeng Kinetics of synthesis of bis-(benzoxazolyl-2-methyl) sulfide (BBMS) is investigated under phase-transfer catalysis conditions. Thus, the reaction of 2-chloromethylbenzoxazole and sodium sulfide is carried out in a two-phase (organic/water) medium, and quaternary ammonium salt and quaternary phosphonium salt are used as phase-transfer catalyst (PTC) in the reaction. The conversion of 2-chloromethylbenzoxazole is dramatically enhanced by adding a small quantity of PTC and is also greatly affected by the reaction conditions. The effects of various reaction variables on the kinetics are investigated, including the amount of catalyst, the temperature, the kinds of catalysts, the kinds of solvents, and the agitation speed. An interfacial reaction mechanism is proposed to explain the characteristics of the reaction. A pseudo-first-order rate model is established to describe the relationship between the fractional conversion and the reaction time. The kinetics data demonstrate that the model is suitable to the reaction of synthesis of BBMS. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 41: 296,302, 2009 [source] 3,5-Bis(n -perfluorooctyl)benzyltriethylammonium Bromide (F-TEBA): An Efficient, Easily Recoverable Fluorous Catalyst for Solid-Liquid PTC ReactionsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 18 2009Gianluca Pozzi Abstract A readily available 3,5-bis(perfluorooctyl)benzyl bromide and triethylamine were reacted under mild conditions to give 3,5-bis(n -perfluorooctyl)benzyltriethylammonium bromide (F-TEBA), an analogue of the versatile phase-transfer catalyst, benzyltriethylammonium chloride (TEBA), containing two fluorous ponytails. This perfluoroalkylated quaternary ammonium salt was successfully employed as a catalyst in a variety of reactions run under solid-liquid phase-transfer catalysis (SL-PTC) conditions. Thus, being both hydrophobic and lipophobic, F-TEBA could be quickly recovered in quantitative yields, and reused without loss of activity over several reaction cycles. [source] Catalytic kinetics of quaternary ammonium poly(styrene- co -methylstyrene) resinAICHE JOURNAL, Issue 7 2006Ho-Shing Wu Abstract The catalytic kinetics and synthesis of poly(styrene- co -chloromethylstyrene) resin of different degrees of crosslinkages and ring substitutions were investigated by copolymerizing styrene and chloromethylstyrene through crosslinking with divinylbenzene. Poly(styrene- co -chloromethylstyrene) quaternary ammonium salt was obtained with activating poly(styrene- co -chloromethylstyrene) resin with tertiary amine. More than 20 types of poly(styrene- co -chloromethylstyrene) quaternary ammonium catalyst were prepared, with reaction conditions including immobilized time (0.125,4 days), concentration of tertiary amine (0.1,2 kmol/m3), kinds of solvents in immobilization (methanol, ethyl alcohol, and DMF), and kinds of tertiary amines (trimethylamine, triethylamine, tripropylamine, tri- n -butylamine, tri- n -pentylamine, tri- n -hexylamine, and tri- n -octylamine). These catalysts were used to achieve the optimum allylation of phenol. The reactions were conducted and studied individually with either equal mole or equal weight of catalyst. The best reactivity for the allylation of phenol was obtained when the structure of the quaternary ammonium catalyst was 10% degree of ring substitution and 2% degree of crosslinkage activating with trihexylamine. The turnover number and the effectiveness factor were also calculated. © 2006 American Institute of Chemical Engineers AIChE J, 2006 [source] Comparison of the Effects of an Ionic Liquid and Other Salts on the Properties of Electrospun Fibers, 2 , Poly(vinyl alcohol)MACROMOLECULAR MATERIALS & ENGINEERING, Issue 1 2009Ganesh Kumar Arumugam Abstract Understanding the effect of conductivity in electrospinning solutions is crucial in order to improve or control the electrospinning process. In this paper the effect of adding small amounts (0.039,0.259 mol,·,kg,1) of three different conductive additives to aqueous solutions of polyvinyl alcohol has been investigated. The salts were HMICl (a room temperature ionic liquid), TEBAC (a quaternary ammonium salt) and KCl. Addition of these salts caused a steady increase in the solution conductivity but the fiber diameter was typically greater than that of PVA alone, and exhibited an oscillatory trend. The oscillatory trend on the fiber diameter is attributed to fiber backbuilding and fusion that occurs prior to deposition on the collector. [source] Organo-vermiculite structure ordering after PVAc introductionPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 6 2007yna Simha Martynková Abstract Natural vermiculite served as a host for intercalation with quaternary ammonium salt (QUAT) followed by in-situ polymerization of polyvinyl acetate (PVAc). We studied the structural changes of organo-vermiculite and its PVAc nanocomposite with the help of X-ray diffraction analysis. The mean crystallite size of PVAc nanocomposite is double compared to that of organo-vermiculite and its distribution of crystallite sizes presents a broader region but more uniform values than the curve calculated for organo-vermiculite. Molecular dynamic calculation proved a monolayer arrangement of QUAT guests and a bilayer-like system of guest organic molecules in the vermiculite gallery. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Novel Anion Exchangers for Electrodes with Improved Selectivity to Divalent AnionsELECTROANALYSIS, Issue 17 2004Vladimir Egorov Abstract It has been found that replacing of several long-chain alkyl substituents at the nitrogen atom of lipophilic quaternary ammonium salts (QAS) by methyls results in a dramatic increase of the potentiometric selectivity of ion-selective electrodes (ISE) with QAS-based plasticized PVC membranes to some divalent anions against the monovalent ones. The discussed effect of QAS cation nature on the potentiometric selectivity is also partly retained for ISE with neutral carrier-based membranes doped with QAS to provide anion permselectivity. This opens up new possibilities to control the potentiometric selectivity of ISE for divalent anions by the appropriate selection of the anion exchanger. [source] Synthesis of novel 1,3-substituted 1H -[1,2,4]-triazole-3-thiol derivativesHETEROATOM CHEMISTRY, Issue 7 2009Karine A. Eliazyan By means of regioselective S-alkylation of 1H-1,2,4-triazole-3-thiol (1), a series of S-substituted derivatives 2a-j were synthesized. In certain conditions, the reaction of 2 with arylsulfochlorides, arylisocyanates, and quaternary ammonium salts of azines corresponding compounds were obtained 1-arylsulfonyl- (3a-d), 1-arylcarbonamido- (4a,b), and 1-azinyl-1,2,4- (6a-p) triazoles. Structures of compounds were confirmed by 1H NMR and elemental analyses. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 20:405,410, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20565 [source] Polyesters based on two silarylene or germarylene moieties: Synthesis under phase-transfer conditionsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2009L. H. Tagle Abstract Polyesters (PEs) containing two heteroatoms (Si and/or Ge) in the main chain, derived from the acid dichlorides bis(4-chloroformylphenyl) ethylmethylsilane, bis(4-chloroformylphenyl) diethylsilane, bis(4-chloroformylphenyl) diethylgermane, and bis(4-chloroformylphenyl) di- nbutylgermane and from the diphenols bis(4-hydroxyphenyl) ethylmethylsilane, bis(4-hydroxyphenyl) diethylsilane, bis(4-hydroxyphenyl) diethylgermane, and bis(4-hydroxyphenyl) di- nbutylgermane, were synthesized under phase-transfer conditions with three quaternary ammonium salts as phase-transfer catalysts and three NaOH concentrations in the aqueous phase. PEs were characterized with IR and NMR spectroscopy, including 29Si-NMR. In general, the yields and intrinsic viscosities were low, and in some cases, an increase in these parameters was shown as a result of the catalyst effect. An increase in the NaOH concentration caused a decrease in the yields because of a hydrolytic process. PEs with Si were thermally more stable than those with Ge. The glass-transition temperatures decreased when the side chains bonded to the heteroatoms were longer. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] Synthesis and characterization of ether derivatives of brominated poly(isobutylene- co -isoprene)JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 2 2006Sergio A. Guillén-Castellanos Abstract Variations of the Williamson ether synthesis were employed to prepare a range of new derivatives of brominated poly(isobutylene- co -isoprene) (BIIR). Unambiguous characterization of the polymeric products was accomplished by spectroscopic comparisons to low-molecular-weight analogues derived from brominated 2,2,4,8,8-pentamethyl-4-nonene, which served as a model for the reactive functionality found within BIIR. The substitution of bromide from BIIR occurred at moderate temperatures with stoichiometric amounts of quaternary ammonium phenoxide to yield O-alkylation products in high yields. Simple mixtures of BIIR, KOH, and aliphatic alcohols generated the desired allylic ethers when heated above 110 °C in the absence of quaternary ammonium salts. Knowledge gained from these small-molecule alkylations was used to prepare graft copolymers from BIIR and poly(ethylene oxide) through the exploitation of the apparent ability of polyethers to activate potassium alkoxides in nucleophilic substitutions. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 983,992, 2006 [source] Synthesis of poly[(2-oxo-1,3-dioxolane-4-yl) methyl methacrylate- co -ethyl acrylate] by incorporation of carbon dioxide into epoxide polymer and the miscibility behavior of its blends with poly(methyl methacrylate) or poly(vinyl chloride)JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 9 2001Sung-Young Park Abstract This study was related to the investigation of the chemical fixation of carbon dioxide to a copolymer bearing epoxide and the application of the cyclic carbonate group containing copolymer-to-polymer blends. In the synthesis of poly[(2-oxo-1,3-dioxolane-4-yl) methyl methacrylate- co -ethyl acrylate] [poly(DOMA- co -EA)] from poly(glycidyl methacrylate- co -ethyl acrylate) [poly(GMA- co -EA)] and CO2, quaternary ammonium salts showed good catalytic activity. The films of poly(DOMA- co -EA) with poly(methyl methacrylate) (PMMA) or poly(vinyl chloride) (PVC) blends were cast from N,N,-dimethylformamide solution. The miscibility of the blends of poly(DOMA- co -EA) with PMMA or PVC have been investigated both by DSC and visual inspection of the blends. The optical clarity test and DSC analysis showed that poly(DOMA- co -EA) containing blends were miscible over the whole composition range. The miscibility behaviors were discussed in terms of Fourier transform infrared spectra and interaction parameters based on the binary interaction model. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1472,1480, 2001 [source] Study on Superabsorbent Composite, 14MACROMOLECULAR MATERIALS & ENGINEERING, Issue 12 2006Preparation of Poly(acrylic acid)/Organo-attapulgite Composite Hydrogels, Swelling Behaviors in Aqueous Electrolyte Solution Abstract Summary: Organo-attapulgite (organo-APT) was prepared by modifying APT using four quaternary ammonium salts with various lengths of the alkyl group, including (octyl)trimethylammonium bromide (OTMABr) and (stearyl)trimethylammonium chloride (STMACl), etc. A series of composite hydrogels, poly(acrylic acid)/organo-APT, from acrylic acid (AA), and organo-APT was prepared by aqueous polymerization, using N,N, -methylenebisacrylamide (MBA) as a crosslinker and ammonium persulfate (APS) as an initiator. The organification and organification degree of APT as well as the corresponding composites were characterized by FTIR, TGA, and XRD. The effects of the length of the alkyl group for different quaternary ammonium salts, organification degree of APT, and organo-APT content on water absorbency and swelling behaviors in various electrolyte solutions were investigated in this study. Equilibrium water absorbency strongly depends on chain length of the alkyl group of quaternary ammonium salts, organification degree of APT as well as organo-APT content. Longer alkyl group, higher organification degree, and proper organo-APT content are of benefit for the improvement of equilibrium water absorbency. Equilibrium water absorbency in distilled water for PAA/APT was enhanced from 350.1 to 562.1 g,·,g,1 after 10 wt.-% organo-APT, modified with STMACl for the highest degree, was introduced. The kind of cation is the key factor influencing equilibrium water absorbency of these composite hydrogels in electrolyte solutions. Organification of APT could enhance responsiveness of the corresponding composite hydrogel to electrolyte solutions. Schematic structure of PAA/organo-APT composite in a dry state (left) and in a swollen state (right). [source] Synthesis of poly[(2-oxo-1,3-dioxolane- 4-yl)methyl methacrylate-co-styrene] by addition reaction of carbon dioxide and its compatibility with poly(methyl methacrylate) or poly(vinyl chloride)POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 7 2002Sung-Young Park Abstract We investigated the chemical fixation of carbon dioxide (CO2) to a copolymer bearing epoxide and the application of the cyclic carbonate group containing copolymer to polymer blends. In the synthesis of poly[(2-oxo-1,3-dioxolane-4-yl)methyl methacrylate-co-styrene] [poly(DOMA-co-St)] from the addition of CO2 to poly(glycidyl methacrylate-co-styrene) [poly(GMA-co-St)], quaternary ammonium salts showed good catalytic activity at mild reaction conditions. The CO2 addition reaction followed pseudo first-order kinetics with the concentration of poly(GMA-co-St). In order to expand the applications of the CO2 fixed copolymer, polymer blends of this copolymer with poly(methyl methacrylate) (PMMA) or poly(vinyl chloride) (PVC) were cast from N,N,-dimethylformamide (DMF) solution. Miscibility of blends of poly(DOMA-co-St) with PMMA or PVC have been investigated both by differential scanning calorimetry (DSC) and visual inspection of the blends, and the blends were miscible over the whole composition ranges. The miscibility behaviors were also discussed in terms of FT-IR spectra. Copyright © 2002 John Wiley & Sons, Ltd. [source] Cyclic Quaternary Ammonium Ionic Liquids with Perfluoroalkyltrifluoroborates: Synthesis, Characterization, and PropertiesCHEMISTRY - A EUROPEAN JOURNAL, Issue 8 2006Zhi-Bin Zhou Dr. Abstract New cyclic quaternary ammonium salts, composed of N -alkyl(alkyl ether)- N -methylpyrrolidinium, -oxazolidinium, -piperidinium, or -morpholinium cations (alkyl=nC4H9, alkyl ether=CH3OCH2, CH3OCH2CH2) and a perfluoroalkyltrifluoroborate anion ([RFBF3],, RF=CF3, C2F5, nC3F7, nC4F9), were synthesized and characterized. Most of these salts are liquids at room temperature. The key properties of these salts,phase transitions, thermal stability, density, viscosity, conductivity, and electrochemical windows,were measured and compared to those of their corresponding [BF4], and [(CF3SO2)2N], salts. The structural effect on all the above properties was intensively studied in terms of the identity of the cation and anion, variation of the side chain in the cation (i.e., alkyl versus alkyl ether), and change in the length of the perfluoroalkyl group (RF) in the [RFBF3], ion. The reduction of Li+ ions and reoxidation of Li metal took place in pure N -butyl- N -methylpyrrolidinium pentafluoroethyltrifluoroborate as the supporting electrolyte. Such comprehensive studies enhance the knowledge necessary to design and optimize ionic liquids for many applications, including electrolytes. Some of these new salts show desirable properties, including low melting points, high thermal stabilities, low viscosities, high conductivities, and wide electrochemical windows, and may thus be potential candidates for use as electrolytes in high-energy storage devices. In addition, many salts are ionic plastic crystals. [source] Heck Reaction Catalyzed by Palladacycle in Neat Water,CHINESE JOURNAL OF CHEMISTRY, Issue 7 2003Jian-Jun Hou Abstract Cyclopalladated ferrocenylimine has been found to be a type of excellent phosphine-free catalyst for Heck reactions in neat water with both higher yields and turnover numbers than those reported in the literature up to now. Some commercial emulsifying agents, including the commonly used quaternary ammonium salts, have been proved to be excellent additives in the catalysis of the reactions. Not only aromatic iodide, but also aromatic bromide could be coupled with the olefins. All reactions were able to be conducted in air under refluxing condition. [source] ,N-Stereogenic Quaternary Ammonium Salts' from L -Amino Acids: Synthesis, Separation, and Absolute ConfigurationHELVETICA CHIMICA ACTA, Issue 4 2009Hua-Fang Wu Abstract Diastereoisomeric linear and cyclic ,N-chiral quaternary ammonium salts' (QASs) were efficiently synthesized from corresponding L -amino acids in high yields. The diastereoisomers of each pair of ,N-chiral QASs' were successfully separated. The absolute configurations of these QASs were determined predominately by X-ray single-crystal analysis. The 1H-NMR data of ,N-chiral QASs' provided characteristic information on the configuration of the N-chiral center. ,N-Chiral QASs' exemplified by [N(R)]- 2a and [N(S)]- 2a are stable in protic and aprotic solvents within a broad pH and temperature range. [source] | |||||||||||||||||||||||||