Showing papers on "Bromide published in 2007"
TL;DR: Two new palladium-catalyzed methods for the direct ortho-arylation of free benzoic acids have been developed and Mechanistic studies of the second method point to the heterolytic C-H bond cleavage as the rate-determining step.
Abstract: Two new palladium-catalyzed methods for the direct ortho-arylation of free benzoic acids have been developed. The first method employs stoichiometric silver acetate for iodide removal, aryl iodide as the coupling partner, and acetic acid solvent. This method is applicable to the arylation of electron-rich to moderately electron-poor benzoic acids and tolerates chloride and bromide substituents on both coupling partners. The second method involves the use of aryl chloride, cesium carbonate base, n-butyl-di-1-adamantylphosphine ligand, and DMF solvent and is suitable for both electron-rich and electron-poor benzoic acids. Mechanistic studies of the second method point to the heterolytic C-H bond cleavage as the rate-determining step.
389 citations
TL;DR: In this article, the effect of halide ions during the seed-mediated growth of gold nanoparticles employing cetyltrimethylammonium bromide (CTAB) as a cationic surfactant system was described.
Abstract: This paper describes the effect of halide ions during the seed-mediated growth of gold nanoparticles employing cetyltrimethylammonium bromide (CTAB) as a cationic surfactant system. With the addition of a small amount of iodide ion (∼20 μM) in a growth solution, the major product of the gold nanostructures formed were notably changed into triangular nanoprisms in the presence of excessive bromide ion (∼0.1 M); otherwise, in its absence, nanorods with an aspect ratio of ∼11 were the main products. The major role of the iodide ion was in retarding the overall rate of crystal growth, and the iodide adsorption appeared to repress the crystal growth along Au(111) direction, resulting in Au(111)-faced triangular nanoprisms. When the counteranions of the surfactant were replaced with chloride ions, a novel nanostructure (i.e., nanorice) was manufactured, which demonstrates the effectiveness of the adsorption of halide ions. However, this finding is quite contrasted with the work of the Sastry group (J. Nanosci. ...
373 citations
TL;DR: Nonspecific nanorod uptake could be greatly reduced by displacing the CTAB surfactant layer with chemisorptive surfactants, particularly by the conjugation of poly(ethylene glycol) chains onto nanorods using in situ dithiocarbamate formation.
Abstract: Gold nanorods coated with cetyltrimethylammonium bromide (CTAB), a cationic micellar surfactant used in nanorod synthesis, were rapidly and irreversibly internalized by KB cells via a nonspecific uptake mechanism. Internalized nanorods near the cell surface were monitored by two-photon luminescence (TPL) microscopy and observed to migrate toward the nucleus with a quadratic rate of diffusion. The internalized nanorods were not excreted but formed permanent aggregates within the cells, which remained healthy and grew to confluence over a 5-day period. Nonspecific nanorod uptake could be greatly reduced by displacing the CTAB surfactant layer with chemisorptive surfactants, particularly by the conjugation of poly(ethylene glycol) chains onto nanorods using in situ dithiocarbamate formation.
304 citations
TL;DR: In this paper, four quaternary ammonium salt monomers were synthesized from dimethylaminoethyl methacrylate (DMAEMA) by quaternization with benzyl chloride (BC), butyl bromide (BB), dodecyl brameride (DB), or hexadecyl bromides (HB), respectively, and the resultant monomers and related polymers were characterized by elemental analysis, FTIR, NMR, thermogravimetric analysis (TGA).
Abstract: Four quaternary ammonium salt monomers were synthesized from dimethylaminoethyl methacrylate (DMAEMA) by quaternization with benzyl chloride (BC), butyl bromide (BB), dodecyl bromide (DB) or hexadecyl bromide (HB), respectively. And then, the monomers were homopolymerized to obtain four polymeric quaternary ammonium materials with different lengths of alkyl chain, which were referred to as poly(DMAEMA-BC), poly(DMAEMA-BB), poly(DMAEMA-DB) and poly(DMAEMA-HB), respectively. The resultant monomers and related polymers were characterized by elemental analysis, FTIR, NMR, thermogravimetric analysis (TGA) and so on. Their bactericidal activities were evaluated by determining minimum bactericidal concentration (MBC) values and inhibitory zone diameters against Gram-positive bacteria ( S. aureus ) and Gram-negative bacteria ( E. coli ), respectively. The results showed that the MBC values of monomer DMAEMA-DB and DMAEMA-HB were 12–24 μg/mL against E. coli and S. aureus . However, the MBC values of monomer DMAEMA-BC and DMAEMA-BB were higher than 50 mg/mL against test microbe. It was very interesting that poly(DMAEMA-BC) and poly(DMAEMA-BB) exhibited greater bactericidal activities than their precursory monomers, but poly(DMAEMA-DB) and poly(DMAEMA-HB) present contrary results.
302 citations
TL;DR: In this article, a linear relationship was found between the logarithm of the critical micelle concentration (cmc) and the number of carbon atoms in the surfactant hydrocarbon chain.
282 citations
01 Jan 2007
TL;DR: A range of surfactant molecular environments within the surface-modified montmorillonite are proposed based upon their thermal decomposition.
Abstract: Surfaces of a Wyoming SWy-2 sodium montmorillonite were modified using microwave radiation through intercalation with the cationic surfactants octadecyltrimethylammonium bromide, dimethyldioctadecylammonium bromide, and methyltrioctadecylammonium bromide by an ion exchange mechanism. Changes in the surfaces and structure were characterized using X-ray diffraction (XRD), thermal analysis (TG) and infrared (IR) spectroscopy. Different configurations of surfactants within montmorillonite interlayer are proposed based on d(001) basal spacings. A range of surfactant molecular environments within the surface-modified montmorillonite are proposed based upon their thermal decomposition. IR spectroscopy using a smart endurance single bounce diamond attenuated total reflection (ATR) cell has been used to study the changes in the spectra of CH asymmetric and symmetric stretching modes of the surfactants to provide more information of the surfactant molecular configurations.
267 citations
TL;DR: The use of organo-clays for cleaning up oil spills is feasible due to its many desirable properties such as high hydrocarbon sorption and retention capacities, hydrophobicity, and recyclability.
216 citations
TL;DR: The experimental results show that the mode of binding of the Cu(II) complex to DNA is classical intercalation and the complex can cleave pBR322 DNA.
191 citations
TL;DR: One example of a "one-pot" process involving Br/I exchange of an aryl bromide and further S-arylation is presented and the recovery and successful reutilisation of the aqueous medium containing the active catalyst is described.
Abstract: A novel protocol for the copper-catalysed S-arylation of thiophenol derivatives with aryl halides leading to diaryl sulfides is reported. The reactions were catalysed by a combination of a copper salt and a 1,2-diamine derivative (acting both as the ligand and as the base) using exclusively water as the solvent. The recovery and successful reutilisation of the aqueous medium containing the active catalyst is described. Furthermore, one example of a "one-pot" process involving Br/I exchange of an aryl bromide and further S-arylation is presented.
169 citations
TL;DR: Water solubility enhancements of polycyclic aromatic hydrocarbons by micellar solutions at 25 degrees C using two series of surfactants, each involving two cationic and one nonionic surfactant in their single as well as equimolar binary and ternary mixed states, were measured and compared.
Abstract: Water solubility enhancements of polycyclic aromatic hydrocarbons (PAHs), viz., naphthalene, anthracene and pyrene, by micellar solutions at 25 °C using two series of surfactants, each involving two cationic and one nonionic surfactant in their single as well as equimolar binary and ternary mixed states, were measured and compared. The first series was composed of three surfactants, benzylhexadecyldimethylammonium chloride (C16BzCl), hexadecyltrimethylammonium bromide (C16Br), and polyoxyethylene(20)mono-n-hexadecyl ether (Brij-58) with a 16-carbon (C16) hydrophobic chain; the second series consisted of dodecyltrimethylammonium bromide (C12Br), dodecylethyldimethylammonium bromide (C12EBr), and polyoxyethylene(4)mono-n-dodecyl ether (Brij-30) with a 12-carbon (C12) chain. Solubilization capacity has been quantified in terms of the molar solubilization ratio, the micelle−water partition coefficient, the first stepwise association constant between solubilizate monomer and vacant micelle, and the average num...
162 citations
TL;DR: In this article, the authors developed a highly efficient method to convert alkenes and CO2 into cyclic carbonates directly in water by using N-bromosuccinimide (NBS) together with 1,8-diazabicyclo[5.4.0]undecenc-7-ene (DBU) in water, or by using a catalytic amount of bromide ion together with aqueous H2O2.
TL;DR: In this article, a novel geminal imidazolium ionic liquid with long hydrocarbon group, 1,4-bis(3-tetradecylimidazolate-1-yl) butane bromide was synthesized and its physicochemical properties were studied.
TL;DR: A new cycloaddition reaction of vinyl ethers with trifluoroethyl acrylate in the presence of a catalytic amount of chiral oxazaborolidine−AlBr3 complex is described which affords [2+2]-adducts with excellent yields and enantioselectivities.
Abstract: Enantioselective [2+2]-cycloaddition pathways to chiral cyclobutanes are rare and not generally utilized for synthesis. A new cycloaddition reaction of vinyl ethers with trifluoroethyl acrylate in the presence of a catalytic amount of chiral oxazaborolidine−AlBr3 complex is described which affords [2+2]-adducts with excellent yields and enantioselectivities. Applications of these adducts to the synthesis of synthetically valuable intermediates are also presented.
TL;DR: The effect of surface roughness on the quartz crystal microbalance with dissipation monitoring (QCM-D) response was investigated and the amount of trapped water was found to increase with the nanoroughness of the adsorbed layer.
Abstract: The effect of surface roughness on the quartz crystal microbalance with dissipation monitoring (QCM-D) response was investigated with emphasis on determining the amount of trapped water. Surfaces with different nanoroughnesses were prepared on silica by self-assembly of cationic surfactants with different packing parameters. We used surfactants with quaternary ammonium bromide headgroups: the double-chained didodecyltrimethylammonium bromide (C12)2DAB (DDAB), the single-chained hexadecyltrimethylammonium bromide C16TAB (CTAB), and dodecyltrimethyl-ammonium bromide C12TAB (DTAB). The amount of trapped water was obtained from the difference between the mass sensed by QCM-D and the adsorbed amount detected by optical reflectometry. The amount of water, which is sensed by QCM-D, was found to increase with the nanoroughness of the adsorbed layer. The water sensed by QCM-D cannot be assigned primarily to hydration water, because it differs substantially for adsorbed surfactant layers with similar headgroups but with different nanoscale topographies.
TL;DR: In this article, the toxicity of ionic liquids, involving different classes of cations and different types of anions, was evaluated by a colorimetric assay with 3-(4,5-dimethylthiazolyl-2)-2,5diphenyltetrazolium bromide (MTT) in two colon carcinoma HT-29 and CaCo-2 cell lines.
TL;DR: The behavior of addition of aromatic acids and their sodium salts on the micellar morphological changes in cationic gemini surfactant solutions is explained in the light of binding of counterions to the micelle as well as the nature of the functional group attached to the additive.
Abstract: In this paper, we are reporting the influence of addition of aromatic acids (anthranilic and benzoic acid) and their sodium salts on the micellar morphological changes in three cationic gemini surfactant solutions, viz. 5 mM tetramethylene-1,4-bis(N-hexadecyl-N,N-dimethylammonium bromide), 10 mM pentamethylene-1,5-bis(N-hexadecyl-N,N-dimethylammonium bromide), and 10 mM hexamethylene-1,6-bis(N,-hexadecyl-N,N-dimethylammonium bromide). The solubilization site of the counterions (obtained from the additives) near the micellar surface are inferred by 1H NMR. The behavior is explained in the light of binding of counterions to the micelle as well as the nature of the functional group attached to the additive.
TL;DR: In this paper, heat capacities and enthalpies of phase transitions for a series of 1-alkyl-3methylimidazolium bromide ionic liquids have been measured by adiabatic calorimetry.
TL;DR: Six 3-D metal-organic frameworks, including two isomeric compounds, have been synthesized and structurally characterized and their crystal structures show various features including various coordination geometries of Zn2+ and various bridging modes of the BTC3- ligands.
Abstract: We have performed ionothermal reactions between Zn(NO3)2 and H3BTC in 1-alkyl-3-methylimidazolium bromide ionic liquids with the alkyl group varying from ethyl to amyl. Six 3-D metal-organic frameworks (MOFs), including two isomeric compounds [Zn3(BTC)2(H2O)2] x 2H2O (1 and 2) (H3BTC = 1,3,5-benzenetricarboxylate acid), [EMI][Zn(BTC)] (3) (E = ethyl, MI = 3-methylimidazolium), [PMI][Zn(BTC)](4) (P = propyl), [BMI]2[Zn4(BTC)3(OH)(H2O)3] (5) (B = butyl), and [AMI][Zn2(BTC)(OH)Br] (6) (A = amyl), have been synthesized and structurally characterized. Compounds 1 and 2 are isomeric compounds, in which the coordination modes of Zn atoms and the BTC3- ligands are considerably different. Compounds 3-6 crystallize with the corresponding ionic liquid cations incorporated in the frameworks. Their crystal structures show various features including various coordination geometries of Zn2+ and various bridging modes of the BTC3- ligands. The incorporated cations appear to have strong interactions with the frameworks.
TL;DR: In this paper, electrical conductivity/concentration data of aqueous solutions of n-hexadecyl-trimethylammonium bromide (CTAB), an cationic surfactant, with two ammonium-based ionic liquids propyl-(2-hydroxyethyl)-dimethyl-ammoniumbromide, (C3Br), butyl-( 2-hydroxethyl)-diammonium Bromide and (C4Br) were determined in the temperature range 298.15-328.15
TL;DR: The first synthesis of fivefold twinned nanorods and right bipyramids of palladium in an aqueous solution, with ascorbic acid as a reducing agent and in the presence of bromide, was described in this article.
TL;DR: In this article, the synthesis of 1,2-phenylenediamine with aldehydes using (bromodimethylsulfonium bromide) at room temperature is described.
TL;DR: Investigation of the role of bromide ion in the formation and speciation of disinfection by-products (DBPs) during chlorination of Buyukcekmece Lake Water in Istanbul concluded that HOBr was found to be 20 times more reactive than HOCl.
TL;DR: A new zwitterionic stationary phase based on silica bonded with 1-alkyl-3-(propyl- 3-sulfonate) imidazolium shows considerable promise for the separation of anions.
TL;DR: In this paper, the effect of the type of salt on the binodal and tie-lines has been studied on the basis of effective excluded volume values of the salt obtained from fitting the Binodal data to the NRTL model and Gibbs free energy of hydration of the constituent ions.
Abstract: Liquid−liquid equilibria (LLE) for the aqueous 1-butyl-3-methylimidazolium bromide, [C4mim]Br, + potassium phosphate and [C4mim]Br + dipotassium hydrogen phosphate systems have been determined experimentally at 298.15 K. The effect of the type of salt on the binodal and tie-lines has been studied on the basis of effective excluded volume values of the salt obtained from fitting the binodal data to the binodal model and Gibbs free energy of hydration of the constituent ions. Furthermore, the extended NRTL model has been used for the correlation of the obtained tie-line data. The six binary adjustable model parameters for this local composition model have been estimated either simultaneously from correlation of the experimental tie-line data or in the calculation; the model parameters between ionic liquid and water or between salt and water have been initially correlated with the vapor−liquid equilibrium (VLE) of the corresponding binary systems, and then those between ionic liquid and salt have been correl...
TL;DR: The hydrogen bonding with fluoride ion, both in formation and in subsequent dissociation, provides remarkable colorimetric and fluorescent changes in the visible region that are advantageous for real-time and on-site application.
Abstract: Pyreno[2,1-b]pyrrole and its dimeric derivative display excellent selectivity and sensitivity for detection of fluoride ion, in comparison with chloride, bromide, iodide, acetate, dihydrogen phosphate, hydrogen sulfate, perchlorate, nitrate, and thiocyanate ions. The hydrogen bonding with fluoride ion, both in formation and in subsequent dissociation, provides remarkable colorimetric and fluorescent changes in the visible region that are advantageous for real-time and on-site application. Detailed NMR and dynamic fluorescence spectroscopic analyses establish the associated mechanism.
TL;DR: T-X phase diagram of the mixture was constructed, which defines the regions of various phases appearing in this mixture, which forms two types of lyotropic liquid-crystalline gels.
TL;DR: In this article, synthetic and structural studies of Pd(II) and Au(I) complexes of a new O-functionalized N-heterocyclic carbene ligand, namely, 1-(o-methoxybenzyl)-3-tert-butylimidazol-2-ylidene, are reported.
TL;DR: Results obtained suggest that formation of nanoparticles is required to lead to a catalytically active system, in contrast to the agglomerates observed when nanoparticles are intentionally preformed.
Abstract: A new family of functionalized ligands derived from norborn-5-ene-2,3-dicarboxylic anhydride has been used in Suzuki C–C cross-couplings between aryl boronic acids and aryl bromide derivatives in [BMI][PF6] (BMI = 1-n-butyl-3-methyl-imidazolium), using palladium acetate as catalytic precursor. High conversions and yields are obtained when amine ligands containing hydroxy groups are involved. TEM analyses after catalysis show the formation of small nanoparticles, in contrast to the agglomerates observed when nanoparticles are intentionally preformed, with a consequent decrease in the catalytic activity in the latter case. Some tests, including the correlation effect between solvent and ligand, are carried out to try to identify the true nature of the catalyst. All the results obtained suggest that formation of nanoparticles is required to lead to a catalytically active system.
TL;DR: In this paper, a comparative study of adsorption of the four compounds on each SMPC adsorbent shows the high adorption capacity of diuron in comparison with its degradation products.
TL;DR: The N,N',N'',N'''-1,2,4,5-tetra(ethylhexanoate) pyromellitamide is found to be capable of both intermolecular aggregation and binding to small anions, and the cooperative anion binding properties and the sensitivity of the self-assembled gels formed by pyromllitamide toward anions could be useful in the development of sensors and switching/releasing devices.
Abstract: The N,N‘,N‘‘,N‘‘‘-1,2,4,5-tetra(ethylhexanoate) pyromellitamide is found to be capable of both intermolecular aggregation and binding to small anions. It is synthesized by aminolysis of pyromellitic anhydride with ethanolamine, followed by a reaction with hexanoyl chloride. The single-crystal X-ray structure of the pyromellitamide shows that it forms one-dimensional columnar stacks through an intermolecular hydrogen-bonding network. It also forms self-assembled gels in nonpolar solvents, presumably by a hydrogen-bonding network similar to the solid-state structure as shown by IR and XRD studies. Aggregation by intermolecular hydrogen bonding of the pyromellitamide is also observed by NMR and IR in solution. Fitting of NMR dilution data for pyromellitamide in d6-acetone to a cooperative aggregation model gave KE = 232 M-1 and positive cooperativity of aggregation (ρ = 0.22). The pyromellitamide binds to a range of small anions with the binding strength decreasing in the order chloride > acetate > bromide >...