The oxidation of alcohols with O-iodoxybenzoic acid (IBX) in aqueous nanomicelles at room temperature

GMPGS-2000, a nonionic amphiphile composed of Guerbet alcohol (2-octyldodecan-1-ol), MPEG-2000 and succinic acid, has been prepared as an effective nanomicelle forming species for the oxidation of alcohols with 2-iodoxybenzoic acid (IBX) in water at room temperature.     

Nanoparticles for catalysis in aqueous media

This review highlights the recent development of nanocatalyst-enabled chemical transformations in water, leveraging the nanomicelle/surfactant chemistry and related technology. Various chemical reactions, including the most frequently used transformations in the pharmaceutical industry, are discussed herein. A potential implementation of such nano-technology in large-scale synthesis at an industry level is also briefly touched on.     

A further application of TPPTS in catalysis: Efficient sucrose-butadiene telomerization using palladium catalysts in water

Sucrose-butadiene telomerization is efficiently carried out in water or water-organic medium in the presence of a palladium salt and TPPTS (TPPTS = trisodium tris(m-sulfonatophenyl)phosphine as catalyst. Mono- and dioctadienylether compounds are selectively obtained using a NaOH 1 M/isopropanol mixture.     

Recent developments in the application of nanoparticles prepared from w/o microemulsions in heterogeneous catalysis

This paper reviews the use of microemulsions, especially the water-in-oil (w/o) microemulsions, for preparation of nanoparticles that are employed as catalyst components in heterogeneous catalytic reactions. The objective is to show the growing interest of using microemulsions in the preparation of different types of materials such as metals, single metal oxides or mixed metal oxides with a broad range of application in heterogeneous catalysis and also in electrocatalysis. In most cases, the catalytic material showed improved catalytic properties as a result of the special synthesis environment created by the microemulsions. Still, research is needed for a better understanding of such beneficial effects. In addition, this method needs improvements in order to produce, in an environmentally friendly way, a suitable amount of material for use in industrial-scale catalytic processes.     

Synthesis of polystyrene-based cationic copolymers and their colloidal properties in water

A series of polystyrene-based cationic copolymers was synthesized by two different methods: (1) solution copolymerization of styrene and vinylbenzyl trimethylammonium chloride (VBTMAC) in ethanol, and (2) surfactant-free emulsion copolymerization of styrene and vinylbenzyl chloride in water followed by reaction with trimethylamine. The results indicated that the different synthesis methods would result in different polymer structures and, therefore, affect the solubility and colloidal properties of the copolymers in water. For the copolymers prepared by method 2, partial crosslinking was observed. The copolymers made by this method are almost water-insoluble. In contrast, the copolymers made from direct copolymerization of styrene and VBTMAC in ethanol are water-soluble or dispersible, but the solubility and the particle size of microaggregates formed by these copolymers in water strongly depend on charge density and temperature. One of the important results from this study is that uniform colloidal particles with a very small particle size (30–50 nm) can be obtained by dispersing polystyrene-based cationic copolymers in water without adding any surfactants. Received: 29 July 1998 Accepted in revised form: 28 September 1998     

Comprehensive study on critical micellar concentrations of SDS in acetonitrile–water solvents

The CMC is one of the fundamental characteristics of surfactants and its determination is crucial for detail understanding of micelles formation. In this study the CMC of SDS in presence of ACN was determined by two independent experimental techniques, capillary electrophoresis and fluorescence correlation spectroscopy (FCS). Yet, studies of SDS micellization in solutions containing ACN as organic modifier are sparse and inconsistent in literature. The measurements were performed for various ACN contents in the range of 0–50% v/v. At ACN contents of up to 10% v/v the CMC is lower when compared to the aqueous solution, while increasing ACN content causes a significant increase of the CMC. Formation of micelles was observed up to ACN concentrations of 35% v/v, which is in contrast to most of the reports in literature. Based on the results of the FCS experiments, we were able to confirm that presence of ACN causes a gradual increase of the size of the micelles with increasing concentration of SDS. Simultaneously, we proved that the classical conductivity approach for the determination of the CMC does not yield reliable results in the presence of higher content of an organic modifier such as ACN.     

Zinc chloride homogeneous catalysis in the tritylation of hydroxyl- and amide-bearing molecules

A tritylation protocol based on the transfer of the triphenylmethylcarbenium ion from trityl acetate to substrates having hydroxyls, in the presence of catalytic amounts of ZnCl₂, is described. The advantages of this method are broad scope, mild conditions, and easy handling. The comparison with the procedure based on the use of equimolar mixture of TrCl and ZnCl₂ in the presence of TEA shows that comparable results are obtained. However, only this method allows reactions of secondary or benzylic alcohols such as oxidation or formation of symmetric ethers to be suppressed. Both procedures are successfully extended to simple and substituted amides. Irrespective of its low solubility in acetonitrile, even asparagine can be directly tritylated on its amide group.     

Efficient dehydrative C-N bond formation using alcohols and amides in the presence of silica supported perchloric acid as a heterogeneous catalyst

Silica supported perchloric acid has been utilized as an efficient heterogeneous recyclable catalyst for N-alkylation of amides (sulfonamides and carboxamides) using alcohols (primary and secondary aliphatic as well as benzylic). The products are formed in high yields within 2-3 h.     

甲酰胺与正负离子表面活性剂有序溶液的研究

对羧酸钠与烷基三甲基溴化铵1：1混合体系的研究表明：常温下各体系在不同比例甲酰胺（FA）／水混合溶剂中，表面张力随浓度变化均有明显的转折点，显示了混合体系中胶团的存在．实验中发现随混合溶剂中FA比例增加，各体系的临界胶团浓度（cmc）增大．在较高温度下发现在甲酰胺中亦存在着因胶团形成而产生的表面张力-浓度对数（γ－logc）曲线的转折点，利用相分离模型对体系胶团热力学参数进行了计算．并探讨了FA对正负离子表面活性剂囊泡的影响．     

Extractability of dioxins from suspended substances in distributed water

The extractability of dioxins from suspended substances (SS) in distributed water was evaluated. Dioxins adsorbed on the collected SS were extracted by pressurized liquid extraction with various solvents. High-polarity solvents (acetone, alcohols) extracted considerably higher amounts of some lower-chlorinated dibenzo-p-dioxins (LoCDDs) than did low-polarity solvents (dichloromethane, toluene), whereas the extracted amounts of higher-chlorinated dibenzo-p-dioxins (HiCDDs) were roughly the same, regardless of the solvent. The extractability of the LoCDDs depended on the isomer. Daily variations in quantities for PCDDs, organic matter (OM), and iron in the SS were examined, and the results suggested that in the SS, LoCDDs and HiCDDs were associated, respectively, with raw water-derived organic matter and microparticles sequestered in iron oxy(hydr)oxide floc. It was also suggested that the low extractability of certain congeners was not attributable to the enormously coexisting ferric compounds but was probably attributable to OM with which they strongly associate.     

Thermodynamics of micelle formation of the ephedrine-based chiral cationic surfactant DMEB in water, and the intercalation of DMEB in montmorillonite

The solubility and the micelle formation of the chiral cationic surfactant (1R,2S)-(−)-N-dodecyl-N-methylephedrinium bromide (DMEB) in aqueous solution were investigated by conductometry and titration microcalorimetry in the temperature range of 278–328 K. The Krafft temperature of DMEB is T_K = 280 K and the solubility of the surfactant at this point is 4.5 mM. The cmc versus T curve passes through a shallow minimum close to room temperature. The micelle formation changes from endothermic to exothermic at this characteristic temperature. The apparent degree of dissociation of the micelles _app increases slightly as the temperature is raised. The isosteric enthalpies of micelle formation, ΔH_{st mic}, are close to the calorimetrically measured enthalpies, ΔH_mic, provided that the real degree of dissociation, _st = 1, is used in the calculations. ΔH_mic and the temperature dependence of ΔH_mic of DMEB are markedly similar to those of sodium dodecylsulfate and dodecyltrimethylammonium bromide. The micelle formation of DMEB is favored by both enthalpy and entropy at and above room temperature. The enthalpy–entropy compensation results in a slight decrease in the Gibbs free energy on increase of the temperature. Sodium montmorillonite (M) was rendered organophilic by DMEB via ion-exchange to produce the clay/organocomplex DME-M. The swelling properties of the organoclay were investigated by XRD measurements in a variety of organic solvents. The basal spacing of DME-M varied from 1.8 to 3.5 nm, depending on the nature of the solvent. DME-M is a heterogenized ephedrine derivative, which may be regarded as a potential catalyst for enantioselective organic syntheses.     

A selective hydration of nitriles catalysed by a Pd(OAc)2-based system in water

In situ formation of a [Pd(OAc)₂bipy] (bipy = 2,2′-bipyridyl) complex in water selectively catalyses the hydration of a wide range of organonitriles at 70 °C. Catalyst loadings of 5 mol% afford primary amide products in excellent yields in the absence of hydration-promoting additives such as oximes and hydroxylamines.     

Efficient synthesis of arylaminotetrazoles in water

Arylaminotetrazole derivatives are synthesized efficiently by the reaction of arylcyanamides and sodium azide in the presence of ZnCl₂ under aqueous conditions at reflux. Generally, isomer of 5-arylamino-1H-tetrazole can be obtained from arylcyanamides carrying electron-withdrawing substituent on aryl ring and as the electropositivity of substituent is increased, the product is shifted toward the isomer of 1-aryl-5-amino-1H-tetrazole.     

Concentration of polyaromatic hydrocarbons in water to sodium dodecyl sulfate-gamma-alumina admicelle

Polyaromatic hydrocarbons (PAHs) in water were concentrated into sodium dodecyl sulfate (SDS)-gamma-alumina and di-2-ethylhexyl sodium sulfosuccinate (Aerosol-OT, AOT)-gamma-alumina admicelles. The comparison of the binding constants (Kad[={adsorbed concentration of the solute (mol/g surfactant)}/{the concentration in the bulk aqueous phase (mol/ml)}] indicated almost the same extraction abilities of the both admicelles. However, better and more reproducible recovery was obtained in the concentration of PAHs into the SDS-gamma-alumina admicelle. PAHs in tobacco smoke that were trapped in water were successfully concentrated into SDS-gamma-alumina admicelle for the HPLC analysis.     

Surfactant-free synthesis of nickel nanoparticles in near-critical water

Nickel nanoparticles have been produced by combining two well-tested methods: (i) the continuous flow supercritical reactor and (ii) the reduction of a nickel salt with hydrazine. The normal precipitation of a nickel-hydrazine complex, which would complicate pumping and mixing of the precursor, was controlled by the addition of ammonia to the precursor solution, and production of nickel nanoparticles with average sizes from 40 to 60 nm were demonstrated. The method therefore provides some size control and enables the production of nickel nanoparticles without the use of surfactants. The pure nickel nanoparticles can be easily isolated using a magnet.     

Kinetics of hydrate formation using gas bubble suspended in water

An innovative experimental technique, which was devised to study the effects of temperature and pressure on the rate of hydrate formation at the surface of a gas bubble suspended in a stagnant water phase, was adapted in this work. Under such conditions, the hydrate-growth process is free from dynamic mass transfer factors. The rate of hydrate formation of methane and carbon dioxide has been systematically studied. The measured hydrate-growth data were correlated by using the molar Gibbs free energy as driving force. In the course of the experiments, some interesting surface phenomena were observed.     

A vibrational CASSCF study of stretch-bend interactions and their influence on infrared intensities in the water molecule

Summary An extension of the multiconfigurational SCF approach for the resolution of the vibrational problem is presented; it follows the philosophy of the CASSCF method developed in Quantum Chemistry. The new method allows a more complete treatment of anharmonic mode couplings, converges much faster and gives a clearer physical insight of vibrational interactions. This is exemplified by the calculation of infrared transition moments in the H₂O and D₂O isotopomers of the water molecule. It is shown how this property varies with the quality of the wave function when vibrational resonances occur. A detailed analysis by means of this new VCASSCF method demonstrates the crucial importance of excited bending oscillators in the intensity of some pure stretching transitions.Boursier F.R.I.A.     

Facile synthesis of Fe@Pd nanowires and their catalytic activity in ligand-free CN bond formation in water

This work reports a facile synthesis of Fe@Pd nanowires. Ligand-free cross coupling reactions of arylboronic acids with various amines in aqueous medium proceed in very good to excellent yield with the use of Fe@Pd nanowires. Furthermore, the catalyst could be easily separated from the reaction mixture using a magnet and could be recycled several times without loss of catalytic activity.     

Selective desorption and analysis of humic substances on suspended particles in river water

The elemental analysis and morphology of individual particles indicate that the dominant suspended particles in river water are kaolin covered with hydrated iron(III) oxide which strongly sorbs humic substances. Suspended particles, about 1 mg, collected from 250 ml of water by centrifugation, are treated with 0.7 ml of 0.1M sodium hydroxide to desorb humic substances. Approximately 60% of copper and 30% of lead on or in suspended particles exist as humic complexes.