Phosphotungstic salt used as an efficient catalyst to rapidly remove RhB from water solution

Ag-modified polyoxometalate [Na(H₂O)]₂[Ag(bpf)]₃[PW₁₂O₄₀] (1) (bpf = 2,4-di(4-pyridyl)furan) was synthesized through a hydrothermal reaction. Single-crystal X-ray diffraction analysis revealed that 1 consists of a hybrid 3D MOF constructed from Keggin-type polyanionic [PW₁₂O₄₀]^3- and cationic Ag-bpf units. Ligand bpf in 1 was in situ transferred from 1,3-bis(4-pyridyl)propane under the higher temperature and pressure of hydrothermal conditions. Catalytic performance of 1 as a heterogeneous catalyst for degradation of organic dye Rhodamine B (RhB) was investigated. Experimental results showed that hybrid 1 was especially active to catalytically degrade RhB under room temperature and natural light. RhB-containing solution (5.0 mg·L^?1) could be quickly bleached in a short time, and the high removal efficiency (97%) could be reached in a mere 30 min. The degradation mechanism of RhB was discussed.     

A Study on the Phosphorylation of Indole,Imidazole, Carbazole,and Phenothiazine Derivatives

Abstract

N-Heterocycles including indolecarbaldehyde, substituted benzimidazoles, and methylimidazole could be efficiently phosphorylated by diethyl chlorophosphate at room temperature in different solvents using alkali carbonate or triethylamine as the base. However, the phosphorylation of N-heterocycles with a lower reactivity at the NH function, such as carbazole and phenothiazine, could not be conducted to complete conversion under the conditions applied.     

Chiral Separation of Ketoprofen on a Chirobiotic T Column and Its Chiral Recognition Mechanisms

Purpose

In this study, direct separation of ketoprofen enantiomers was performed on a Chirobiotic T column.

Methods

The effects of the type and amount of the organic modifier, buffer concentration, pH value, temperature and flow rate on retention and selectivity were investigated. Experiments were carried out in the temperature range of 20–40 °C to study the effects of temperature. Thermodynamic parameters were calculated from plots of ln k or ln α versus 1/T. Molecular dynamics simulation was done to investigate interactions between ketoprofen enantiomers and the chiral selector—teicoplanin.

Results

It was observed that pH and flow rate had a large influence on resolution. Baseline separation of ketoprofen enantiomers could be achieved with low amounts of methanol, high temperature and high buffer concentrations.

Conclusions

Results from a thermodynamic study and molecular dynamics simulation show that steric hindrance effect, π–π complexation, hydrogen bonding and electrostatic forces are the main driving forces which cause chiral recognition of ketoprofen enantiomers.

     

Synthesis and phase behaviour of new biodegradable liquid crystalline polycarbonate derived from side chain cholesteryl derivative

A new cholesterol side-functionalised polycarbonate was synthesised through a coupling reaction between the terminal carboxyl group of the monomer 6-cholesteroxy-6-oxocaproic acid (COHA) and side hydroxyl group of the polycarbonate (PHTMC). The chemical structures of the intermediate compounds, monomers and polymers obtained in this study were characterised with FT-IR and ¹H NMR spectrum. Their phase behaviour and thermal stability were investigated using polarising optical microscopy, differential scanning calorimetry, X-ray diffraction and thermogravimetric analysis. The monomer COHA showed a cholesteric phase, while the corresponding cholesterol side-functionalised polycarbonate P(TMC-g-COHA) revealed a smectic A phase. This behaviour was attributed to an increased density of the mesogenic units in side chain and hence an ordered organisation into the mesophase. Furthermore, P(TMC-g-COHA) could exhibit a liquid crystalline state below body temperature (≈37°C). This fact indicated it could be used clinically as a self-assemble material with orientational-order mesophase. In addition, P(TMC-g-COHA) had a good thermal stability, the corresponding thermal decomposition temperature was 241°C.     

锰离子参与的类Fenton反应的HPLC和ESR波谱研究

利用自旋捕捉-ESR技术及芳环羟基化反应-高效液相色谱(HPLC)法两种方法研究了Mn^2＋参与的类Fenton反应. 两种方法均检测到Mn^2＋与H₂O₂反应产生•OH. 建立了HPLC-荧光检测器对•OH的高灵敏快速检测方法. 检测了超氧化物歧化酶以及几种Mn^2＋配体对产生•OH的影响. 结果显示, Mn^2＋与H₂O₂反应可以发生类Fenton反应, 产生•OH. 这一现象可能是Mn^2＋引起生物体内氧化损伤的重要原因.     

Silica sulfate as an efficient recyclable catalyst for protection of α-hydroxy acids with cyclohexanone

Silica sulfate has been found to be an effective catalyst for protection of α-hydroxy acids under mild reaction conditions. Although the reaction can be carried out in diethyl ether, a remarkable rate enhancement was observed when the reaction was carried out under solvent-free condition. The catalyst could also be recovered and reused without any significant loss of reactivity. A wide range of α-hydroxy acids could be protected using cyclohexanone derivatives in high yield in presence of silica sulfate catalyst at room temperature.     

Cellulose sulfuric acid: reusable catalyst for solvent-free synthesis of bis(indolyl)methanes at room temperature

Abstract

Bis(indolyl)methanes were synthesized from indole and aldehydes under solvent-free conditions using cellulose sulfuric acid (CSA) as a catalyst at room temperature. CSA is easily prepared and it was also found that this catalyst could be recovered quantitatively and reused without much loss of catalytic activity.     

Synthesis and Characterization of Amphiphilic Block Copolymer by Block Copolymerization of Butadiene and Acrylamide using Macroazoinitiator

Abstract

Macroazoinitiator (MAI) was prepared from hydroxyl‐terminated polybutadiene (HTPB) and 4,4′‐azobis‐4‐cyanopentanoic acid by direct polycondensation in the presence of 1‐methyl‐2‐chloropyridinium iodide at room temperature. This MAI used for block copolymerization of AAm at 60°C gave the best results in chloroform but the formation of a crosslinked product could not be ruled out in dioxane. It was inferred that for production of a linear block copolymer, homogeneous reaction mixture was required.

The resulting products were characterized by spectral studies IR and NMR, viscosity measurements. Distinct phase segregation of hydrophobic and hydrophilic blocks was evident through DSC analysis.     

Clean Procedure for the Synthesis of α-Aminophosphonates Catalyzed by Biodegradable Ionic Liquid

Abstract

A biodegradable SO₃H-functionalized ionic liquid (IL) was prepared and used as the catalyst for a one-pot, three-component condensation synthesis of α-aminophosphonates from aldehydes, amines, and triethylphosphite/diethylphosphite at room temperature under solvent-free conditions or in aqueous media. The products could be simply separated from the reaction mixture and the catalyst could be recycled and reused for several times without noticeably reducing catalytic activity.     

A Simple and Selective Oxidation of Sulfides to Sulfoxides Using Tetrabutylammonium Peroxydisulfate: A Rebuttal

Abstract

The report that oxidation of sulfides to sulfoxides using tetrabutylammonium peroxydisulfate (2) in methylene chloride was found to be erroneous. We repeated the procedure described in the paper and found that oxidation of sulfide to sulfoxide could not be achieved with the method.     

Poly(Crown Ether) Catalyzed Derivatization of Lower Fatty Acids for Gas Chromatography

Abstract

Poly (crown ether) was employed as a catalyst of derivatization of lower fatty acids to the p-bromophenacyl esters for gas chromatographic determination of them. The esterification reaction proceeds quantitatively under mild conditions, i.e. at room temperature and within 30 min. The poly (crown ether) did not interfere with the gas chromatogram of the esters unlike monomeric crown ethers. Normal fatty acid (C₁-C₆) and the isomers could be determined simultaneously near to the detection limit of FID.     

Temperature- and Concentration-dependency of the Electrical Resistivity of Molten Ag-Mg-, Cu-Sb-, and Zn-Sn-alloys

Abstract

The electrical resistivity was measured in the liquid systems Ag-Mg, Cu-Sb, and Zn-Sn. With the eutectic system Zn-Sn the resistivity shows a convex smooth run between the values of the pure components. With the systems Cu-Sb and Ag-Mg the resistivity shows maxima at the concentrations of the solid intermetallic compounds. The relative superelevation of these maxima decreases with rising temperature, corresponding to the decay of “compound-molecules” in the melt.

With the system Zn-Sn the small maxima found by Roll and Motz could not be confirmed. Also no influence of the magnetic susceptibility on the run of resistivity vs. concentration could be detected during the measurements in a rotating field apparatus.

A convincing consistency of the measured values of the electrical resistivity in the system silver-magnesium with those values, which were obtained by calculation from X-ray data is shown.     

Enantioselective solvent-free Robinson annulation reactions

The enantioselective cyclization of the prochiral cyclic substrates1 to7 and26, can be carried out in theneat using S-proline as catalyst. The substrates18 to22 and27 could not be cyclized with S-proline but could be cyclized with a mixture of S-phenylalanine and d-camphorsulphonic acid. The enantioselective cyclization of prochiral acyclic triones45 and47 and also the racemic tricarbonyl compounds54 to57 could also be carried out in theneat using S-proline as catalyst. The optically active enediones obtained in the above cyclizations could also be obtained directly from 1,3-diones or 2-hydroxymethylene cycloalkanones in a one-pot reaction with methyl vinyl ketone (MVK) and S-proline in the absence of solvents.¹³C NMR studies of the one-pot synthesis ofS-11 andS-14 reveal that the annulations involve initial formation of an acid-base complex followed by a Michael reaction and then an enantioselective cyclization. Such enantioselective cyclizations probably occur on the surface of S-proline crystals.     

A Critical Assessment of Particle Temperature Distributions During Plasma Spraying: Experimental Results for YSZ

Plasma sprayed coatings of Yttria Stabilized Zirconia (YSZ) have been studied extensively through the years to understand variations in coating properties as well as to achieve control on microstructure of the coatings. The requirement for microstructural control and reliability have become all the more important as coatings have now become part of an integrated “prime reliant” design strategy aimed at increasing turbine inlet temperature and associated efficiencies. One of the important thrusts in monitoring and controlling the process has been the application of process sensors that measure spray stream characteristics, notably particle temperature and velocity. Although single particle-based measurements have been available for some time, in general control strategies based on particle state rely on average values of temperature and velocity. In this study, a detailed examination of particle temperature distributions is presented. When systematically examined over a wide range of operating conditions of the resulting range of particle temperatures, a significant structure in the statistical distribution has been observed. A close inspection of the data indicates that this distribution can be interpreted as melting state indicator for YSZ. A characteristic peak at the melting point of ZrO₂ (error in absolute T-measurement is ≈ ±10%) can be used as an indicator for re-solidified particles. In the past, control strategies based on process diagnostic sensors have been based on average particle temperatures and velocities. Although the average values seem to be promising as control parameters, it has been shown through our results that different melting states could be demonstrated for the same average T and V settings. The melting state in turn has an important bearing on the coating structure and properties. It therefore implies that a process control strategy (to maintain coating quality) based on in flight particle sensors will have to take these findings into account. As an example, one strategy of process control would not only define the process in terms of the average particle temperature and velocity but also include the effect that parameter changes have on distributions.     

One-Pot Synthesis and Methylation of 3-[2-(1H-Benzimidazol-2-yl-Sulfanyl)-Acetyl]-Chromen-2-Ones

Abstract

3-(2-Bromoacetyl)coumarins (I), when treated with 2-mercatobenzimidazole (II) in acetone containing K₂CO₃ (mild base) and tetrabutylammonium bromide (TBAB) as a phase transfer catalyst, at room temperature yielded the title compound 3-[2-(1H-benzimidazole-2-yl-sufanyl)-acetyl]-chromen-2-one (III) in a one-pot synthesis. Alternatively, III could also be prepared by treating dithiocarbonic acid O-ethyl ester, S-[2-oxo-2-(2-oxo-2H-chromen3-yl)-ethyl] ester (V), with o-phenylenediamine (VI). The methylation of the title compound III was performed with dimethyl sulfate (DMS), in acetonitrile containing TBAB and K₂CO₃ at room temperature, resulting in 3-[2-(N-methyl-benzimidazol-2-yl-sulfanyl)]-acetyl-chromen-2-ones (VII). Alternatively, methylation of III could also be performed with DMS in acetonitrile containing K₂CO₃ as base and clay as surface catalyst. All the compounds were synthesized in good yields and their structures were confirmed by spectral and analytical data.

[Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements for the following free supplemental resource: ¹H NMR of IIIB, VB and VIIB]     

A green oxidation protocol for the conversion of secondary alcohols into ketones using heterogeneous nanocrystalline titanium (IV) oxide in polyethylene glycol

Abstract

The oxidation of secondary alcohols into corresponding ketones has been described using heterogeneous nanocrystalline TiO₂ as catalyst at a moderate temperature with quantitative yields. Use of H₂O₂ instead of O₂ (g) is the main feature of our methodology since maintenance of P_O2 (g) at elevated temperature is not easy. Besides, this catalyst could be recovered and reused for further reactions with consistent activity. Hence, our present protocol is economical and throughout clean consisting of green reagent, solvent, and catalyst.     

Synthesis and immunological study of a wall teichoic acid-based vaccine against E. faecium U0317

ABSTRACT

A repeat unit of cell wall teichoic acids (WTA) isolated from E. faecium U0317 was chemically synthesized efficiently by a stepwise strategy. It was derivatized with a 5-aminopentanyl linker to facilitate conjugation with carrier proteins KLH and HSA. Immunological studies of the KLH conjugate 1 demonstrated that it could provoke robust immune responses and high titers of IgG antibodies, which could successfully recognize the synthesized WTA repeat unit 3. This result suggested that synthetic glycoconjugate 1 could be a promising vaccine candidate against E. faecium for further studies.     

含卤素端基的单取代对-叔丁基杯[6]芳烃的合成与表征

用THF作为反应溶剂, K₂CO₃作碱, 对-叔丁基杯[6]芳烃与二溴丁烷、二溴己烷和1,4-二氯丁炔-2反应以中等产率选择性地合成了含有卤素端基的单取代对-叔丁基杯[6]芳烃2a～2c. 2a和2b可与对甲苯磺酸甲酯(MeOTs)反应高产率地得到全甲基化产物3a和3b. 通过核磁共振谱(¹H NMR)和质谱(FAB-MS)表征, 发现所有化合物都具有预期结构, 2a～2c和3b在室温下是锥式构象, 而3a没有固定构象.     

Characterization of storage stability of resol resin solutions via gel time measurement and high-performance liquid chromatography

The influence of the temperature of storage on the proceeding polycondensationof commercial resol resin solutions was analyzed and it was found that results derived from a simple gel time measurements can provide the necessary information. It could be shown that resol resin solutions can be fitted into Arrhenius like models, which allow an extrapolation of the temperature-dependent changes of the material over arbitrary temperature ranges and hence estimation of the prolongation or reduction of declared shelf-life. High-performance liquid chromatographic analyses of the content of free phenol and free formaldehyde during storage could confirm and widely explain the observations from gel time measurements.     

Synthesis of a series of triple-bridged cyclotriphosphazene hexa-alkoxy derivatives and investigation of their structural and mesomorphic properties

Triple diamino-bridged cyclotriphosphazene (1) was reacted in a 1:8 stoichiometry with the sodium derivatives of long-chain diols [1-octanol, 1-decanol, 1-dodecanol, 1-hexadecanol] tetrahydrofuran (THF) at room temperature to form hexa-substituted cyclotriphosphazene derivatives (2, 3, 4 and 5, respectively), whose mesomorphic behaviours were investigated for their possible applications as liquid crystals. The cylindrical-type cyclotriphosphazene derivatives (2–5) were characterised by mass and elemental analyses and by Fourier transform infrared spectroscopy (FT-IR), ¹H and ³¹P {¹H} NMR spectroscopies. The thermal and mesomorphic properties were investigated by differential scanning calorimetry and by polarising optical microscopy, respectively. It was found that liquid crystal materials could be obtained from compounds 3 and 4 with alkoxy chains rather than using aromatic ring(s) as mesogens as published previously.