Reflux In Water Research Articles

Study on the in situ sulfidation and electrochemical performance of spherical nickel hydroxide

In this paper, atmospheric reflux in water is used to directly form a nickel sulfide layer in-situ with excellent conductivity sulfide on the surface of spherical nickel hydroxide particles, significantly improving the conductivity of nickel hydroxide particles. The experimental results show that the spherical Ni(OH)2@NiS material synthesized by the in situ sulfurization method. As the cathode active material of nickel-iron batteries exhibits excellent electrochemical performance, especially high-rate discharge and cycle performance, which are better than nickel hydroxide electrodes with cobalt oxide. The atmospheric reflux method in water has a simple process and equipment and has no pollution to the environment. Spherical Ni(OH)2@NiS materials synthesized by in situ vulcanization can completely replace nickel hydroxide material with cobalt, and they have great commercial application value and market competitiveness as cathode active materials for alkaline nickel-based batteries.

Dynamic enzymatic synthesis of γ-cyclodextrin using a photoremovable hydrazone template

Dynamic enzymatic synthesis of γ-cyclodextrin using a photoremovable hydrazone template

Robust Aluminum and Iron Phosphinate Metal-Organic Frameworks for Efficient Removal of Bisphenol A.

Porous metal-organic frameworks (MOFs) have excellent characteristics for the adsorptive removal of environmental pollutants. Herein, we introduce a new series of highly stable MOFs constructed using Fe3+ and Al3+ metal ions and bisphosphinate linkers. The isoreticular design leads to ICR-2, ICR-6, and ICR-7 MOFs with a honeycomb arrangement of linear pores, surface areas up to 1360 m2 g-1, and high solvothermal stabilities. In most cases, their sorption capacity is retained even after 24 h of reflux in water. The choice of the linkers allows for fine-tuning of the pore sizes and the chemical nature of the pores. This feature can be utilized for the optimization of host-guest interactions between molecules and the pore walls. Water pollution by various endocrine disrupting chemicals has been considered a global threat to public health. In this work, we prove that the chemical stability and hydrophobic nature of the synthesized series of MOFs result in the remarkable sorption properties of these materials for endocrine disruptor bisphenol A.

Dehydrogenative Transformation of Alcoholic Substrates in Aqueous Media Catalyzed by an Iridium Complex Having a Functional Ligand with α-Hydroxypyridine and 4,5-Dihydro-1H-imidazol-2-yl Moieties

A new catalytic system that employs water as an environmentally friendly solvent for the dehydrogenative oxidation of alcohols and lactonization of diols has been developed. In this catalytic system, a water-soluble dicationic iridium complex having a functional ligand that comprises α-hydroxypyridine and 4,5-dihydro-1H-imidazol-2-yl moieties exhibits high catalytic performance. For example, the catalytic dehydrogenative oxidation of 1-phenylethanol in the presence of 0.25 mol % of the iridium catalyst and base under reflux in water proceeded to give acetophenone in 92% yield. Additionally, under similar reaction conditions, the iridium-catalyzed dehydrogenative lactonization of 1,2-benzenedimethanol gave phthalide in 98% yield.

Synthesis of Some Hexahydroquinazolinones Using K<sub>3</sub>AlF<sub>6</sub>(Al<sub>2</sub>O<sub>3</sub>/KF) as an Efficient Catalyst in Some Hexahydroquinazolinone Derivatives

A protocol for the synthesis of some 4-Aryl-1,3,4,6,7,8-hexahydroquinazolin-2,5(1H,6H)-diones (HHQs) was developed by means of a three-component condensation reaction of an aromatic aldehyde, 1,3-cylohexadione and urea in the presence of K3AlF6 (Al2O3/KF) as catalyst. This reaction is carried out under different conditions including 1) solvent free; 2) reflux in acetonitrile; 3) reflux in ethanol; 4) reflux in chloroform; and 5) reflux in water. In all conditions, the desired products are obtained in high yields after relatively short reaction times. Nevertheless, the reactions proceed faster and in higher yields when they were carried out in acetonitrile. This adopted protocol for some Biginelli-type products has offered the advantages of reusability of the catalyst, high yields and ease of separation of pure products. Furthermore, the catalyst is easily prepared, stabilized and efficiently used under reaction conditions.

Degradation of fluoride-free MIL-100(Fe) and MIL-53(Fe) in water: Effect of temperature and pH

The degradation in liquid water of two iron-containing MOFs MIL-100(Fe) and MIL-53(Fe) synthesized in fluoride-free conditions was studied. It was found that dispersing the MOFs in deionized water (1 mg/mL) results in the decrease of pH to 2.9 for MIL-100(Fe) and to 4.5 for MIL-53(Fe). Given this finding the stability of the MOFs in liquid water was characterized under two different sets of conditions: 1) reflux in water at 100 °C under obtained pH and 2) at ambient temperature under adjusted pH 7. After reflux of MIL-100(Fe) at 100 °C its XRD pattern remains unchanged, however a strong decrease of its BET surface area and appearance of α-Fe2O3 nanoparticles point out to a partial degradation of the MOF. Reflux of MIL-53(Fe) in water at 100 °C results in its partial degradation yielding H2BDC molecules intercalated in the pores of the remaining MOF particles. To study the degradation of MIL-100(Fe) and MIL-53(Fe) under adjusted pH 7 at room temperature the solids were dispersed in water and then NaOH solution was added in order to maintain a constant pH value. It was found that under such conditions the frameworks of both materials collapse yielding poorly crystallized 6-line ferrihydrite. This finding suggests that the notion of “stability in deionized water” frequently used for MOFs needs to be completed by specifying the exact pH value at which the tests are realized.

An efficient synthesis of 3-indolyl-3-hydroxy oxindoles and 3,3-di(indolyl)indolin-2-ones catalyzed by sulfonated β-CD as a supramolecular catalyst in water

Sulfonated-β-cyclodextrin (β-CD-SO3H) promoted efficient and fast electrophilic substitution reaction of indoles with various isatins reflux in water is reported affording various 3-indolyl-3-hydroxy oxindoles and 3,3-di(indolyl)indolin-2-ones in good to excellent yields in short reaction time.

MIL-53(Al) under reflux in water: Formation of γ-AlO(OH) shell and H2BDC molecules intercalated into the pores

It is shown that treatment of MIL-53(Al) (Al(OH)BDC·H2O, BDC = 1,4-benzene dicarboxylate) under reflux in water results in a progressive transformation of the solid into a new well crystallized phase. After reflux for 10h or more the new phase is obtained in a pure form and its XRD pattern was indexed in a monoclinic system with the following cell parameters: a=19.47Å, b=8.98Å, c=6.60Å, β=107.7°. Characterization of the obtained solid by TGA, FT-IR, NMR, TEM and XRD has revealed that its composition is [0.8Al(OH)BDC·0.2H2BDC]+0.2γ-AlO(OH). Formation of this material indicates that under reflux in water a partial hydrolysis of the MOF network occurs producing H2BDC molecules (occluded in the pores) and γ-AlO(OH) species. The latter is shown to form a thick shell (100–200nm) consisting of strongly crumpled sheets of 3nm of thickness. Formation of γ-AlO(OH) under reflux in water allows to use such treatment as an easy way to modify the surface properties of MIL-53(Al). We showed that treatment of MIL-53(Al) under reflux in water for a short time (<1h) yields a thin layer of γ-AlO(OH) on the surface of the particles while only slightly decreasing their pore volume (from 0.57 to 0.50cm3/g). Such surface modification of MIL-53(Al) might be useful from two points of view. First, it creates a strongly hydrophilic layer on the surface of material and may thus facilitate its shaping. Second, the OH groups of γ-AlO(OH) surface layer may be used as anchoring sites for functionalization of MIL-53(Al) particles.

Therapeutic Effects of Annona senegalensis Pers Stem Bark Extracts in Experimental African Trypanosomiasis

Purpose: To evaluate the efficacy of the stem bark extracts in the treatment of model Trypanosoma brucei brucei infection in mice. Methods: Powdered stem bark of A. senegalensis was sequentially extracted under reflux in hexane, methanol and water and the extracts were investigated for their efficacies in the treatment of albino mice infected with T.b brucei. Blood and cerebrospinal fluid infectivity (CSF) tests were done to confirm cure of infection. Results: Hexane extract, at a dose of 400 mg/kg body weight and aqueous extract at a dose of 300 mg/kg body weight, cured the experimental infection in mice. Blood and CSF infectivity tests confirmed cure of infected animals. Conclusion: The two different extracts of the same plant being efficacious brings hope that appropriate combinations of preparations from these extracts or preparations thereof may help in overcoming the problem of resistance, a major limitation of current chemotherapy, since the different extracts may be acting by different mechanisms.Keywords: Trypanosoma, anti-trypanosome, chemotherapy, trypanocidal, sleeping sickness

Methodology for Synthesizing Crystalline Metallosilicates with Expanded Pore Windows Through Molecular Alkoxysilylation of Zeolitic Lamellar Precursors

Postalkoxysilylation with diethoxydimethylsilane has been carried out on the zeolitic lamellar precursors of various topologies such as MWW, FER, CDO and MCM-47 aiming to construct new crystalline structures with expanded pore apertures between the layers. The silylation process and the crystalline and pore structures of the resulting materials have been investigated with the techniques of XRD, IR, (13)C and (29)Si MAS NMR, ICP, SEM, HRTEM, elemental analyses, and N 2 adsorption. In contrast to forming known three-dimensional zeolite structures after direct calcination of the lamellar precursors, the silylation led to new crystalline structures with opener pores, as evidenced by the shift of layer-related diffractions to the lower-angle region in XRD patterns and the enlarged interlayer pores found by HRTEM images. After optimizing the treatment conditions, particularly the amount of silane agent, a maximum and homogeneous silylation was realized, which guaranteed the phase purity in interlayer expanded zeolites. The expanded structures were well preserved after calcination at 823 K or reflux in water for 1 to 2 weeks, indicating a high thermal stability and also a hydrothermal stability. The interlayer expanded zeolites prepared from the metallosilicate precursors of MWW topology exhibited higher catalytic activities in the redox and solid acid-catalyzed reactions of bulky molecules than that of their counterparts with conventional MWW topology.

Nitrogen-Rich Tetrazolium Azotetrazolate Salts: A New Family of Insensitive Energetic Materials

The metathesis reaction of sodium azotetrazolate with tetrazolium iodides 5and 6 at reflux in water yielded dihydrated species in both instances (1 and 3, respectively). However, when silver azotetrazolate (Ag2ZT) was used instead of the sodium salt in dry methanol, the anhydrous compounds 2 and 4 formed. An alternative synthesis for 2 and 4 that avoids handling highly sensitive Ag2ZT is introduced. All materials were fully characterized by means of elemental analysis, mass spectrometry (MS), and vibrational (IR, Raman) and NMR (1H, 13C) spectroscopy. Additionally, the crystal structures of the new compounds were determined (1, monoclinic, P21/c; 2–4, triclinic,P1̅). A discussion of the hydrogen bonding by means of graph-set analysis is provided. The thermal behaviors of 1–4 and their constant volume energies of combustion were assessed by DSC and bomb calorimetry measurements, respectively. Their sensitivity to shock, friction, and electrostatic discharge was measured by submitting the compounds to standard tests. The detonation pressures and velocities were calculated from the energies of formation using the EXPLO5 code (1, P = 20.2 GPa, D = 7820 m s−1; 2, P = 20.0 GPa, D = 7803 m s−1; 3, P = 22.4 GPa, D = 8090 m s−1; and 4, P = 21.1 GPa, D = 7977 m s−1. Lastly, the decomposition products were both calculated and experimentally determined.

Synthesis of hydrothermally stable aluminium-containing ethane-silica hybrid mesoporous materials using different aluminium sources

Aluminium-containing ethane-silica hybrid mesoporous materials having ethane groups in the frame wall positions are synthesized using aluminium isopropoxide as well as aluminium nitrate as the aluminium sources. The materials were characterized in detail using powder XRD, N 2 adsorption–desorption, SEM, TEM, TG-DTG, TPD, 29Si, 13C and 27Al MAS NMR techniques. Characterization techniques revealed that aluminium isopropoxide was the appropriate source for the synthesis of organo aluminosilicas on considering the structural ordering, acidity as well as the percentage of aluminium incorporation into the ethane bridge. 27Al MAS NMR displays aluminium as tetrahedrally coordinated in both the aluminium-containing organosilicas. Unlike the conventional EtOH–HCl template extraction process, in the present studies, we had used EtOH–NH 4OH as the surfactant-extracting medium and chemical analysis results suggest that using this procedure the extent of dealumination can be greatly reduced. XRD and nitrogen physisorption studies further proved that the materials are hydrothermally stable, that the ordered pore channels retains its structure even after 150 h reflux in boiling water, while the conventional Al-MCM-41 catalyst collapsed its mesostructure after 50 h reflux in water. The improved hydrothermal stability of the hybrid materials, even in presence of sodium ions, is attributed to the thick pore walls as well as due to the presence of hydrophobic bridging ethane groups in the wall positions.

Reactions at the azomethine CN bonds in the nickel(ii) and copper(ii) complexes of pyridine-containing Schiff-base macrocyclic ligands

Template condensation between 2,6-dicarbonylpyridines and a tripodal tetramine tris(3-aminopropyl)amine in the presence of copper(II) or nickel(II) yielded macrocyclic complexes that contained a coordinated primary amine as an appended functional group. The derivatives of 2,6-diformylpyridine contained labile azomethine bonds susceptible to water or alcohol addition, and were isolated in the form of crystallographically characterized hemiaminals or O-ethyl hemiaminals. The nickel(II) hemiaminal complex produced a macrocyclic product upon reduction with sodium borohydride, and the structures of the two complexes had very similar ligand conformations. The derivatives of 2,6-diacetylpyridine formed stable Schiff-base macrocycles with rigid, nearly planar structures in which azomethine bonds were conjugated with the pyridine ring. The steric strain was relieved upon heating of the complexes in water–alcohol media. The products were determined by the coordination requirements of the metal ions: the copper(II) underwent a CN double bond shift, forming a more flexible five-coordinate macrocyclic complex, whereas the nickel(II) compound underwent a partial ring-opening hydrolysis, giving rise to a pseudo-octahedral six-coordinate species. The unusual isomerization of the copper(II) complex was accompanied by H/D exchange at CH-bonds, and was facilitated by alcohol addition. The mechanism of isomerization is similar to B6-catalyzed transamination reactions (D.E. Metzler, M. Ikawa and E.S. Snell. J. Am. Chem. Soc., 1954, 76, 648). The corresponding four-coordinate copper(II) complex lacking a pendant arm was more thermally stable than its five-coordinate counterpart, and underwent partial double-bond migration under harsh conditions (prolonged heating at reflux in water–ethanol mixtures at pH > 8.5).

Effect of wettability and ageing conditions on the physical and mechanical properties of uniaxially oriented jute-roving-reinforced polyester composites

In order to obtain reliable composite materials in structural applications and to utilise fully the potential of reinforcing fibres, both perfect impregnation and strong interfacial bond formation have to be guaranteed. In the present study the tensile, flexural, and impact behaviour of jute roving reinforced polyester composites were investigated as a function of fibre loading and fibre surface wettability. Two types of unsaturated polyesters viz; (a) Resana having a wetting agent and (b) Elekeiroz without wetting agent, were used to study the influence fibre surface wettability. It was noted that Resana polyester composites showed mechanical properties superior to those of Elekeiroz composites. The impact strength of the Resana polyester composite with 30% fibre content was found to be 80 J/M 2, which is about 350% higher than that of the polyester matrix. Jute rovings were alkali treated in 10% aqueous NaOH solution for 3 h periods under two different conditions, i.e. (a) immersion at room temperature and (b) reflux at 100°C. It was observed that jute rovings refluxed in alkali for 3 h showed better tensile properties than those treated at room temperature. The mechanical properties of the jute Resana polyester composites were evaluated under three ageing conditions, i.e. (1) immersion in water at 50°C for 48 h (2) under reflux in water for 2 h; and (3) thermal ageing in an air circulating oven at 100°C for periods up to 8 days. Our results indicate that the composites refluxed in water for 2 h showed a slight improvement in their tensile properties compared to those of immersion-aged composites. It was observed that thermal ageing tended to decrease the composite mechanical properties, which was attributed to oxidative degradation of both fibre and matrix.

Preparation and reactions of bromo-2-nitro- and bromo-2-aminoimidazoles

Treatment of 1-methyl-2-nitroimidazole with bromine in water resulted in rapid dibromination to give 4,5-dibromo-1-methyl-2-nitroimidazole. In dioxane, the bromination was slower, and could be controlled to give 4-bromo-1-methyl-2-nitroimidazole 5 and 5-bromo-1-methyl-2-nitroimidazole 6 in a 4:1 ratio. In an attempt to displace the bromine, the monobromo compounds were treated with cysteamine hydrochloride. In each case the nitro group was displaced instead, the 4-bromo 5 resulting in 2-[(2-aminoethyl)thio]-4-bromo-1-methylimidazole 9 as sole product, and the 5-bromo 6 giving two products identified as the monosubstituted 2-[(2-aminoethyl)thio]-5-bromo-1-methylimidazole 13 and the disubstituted 2,5-bis[2-(aminoethyl)thio]-1-methylimidazole 12. The latter product forms by further reaction of the former and was the sole material observed at long reaction times. A fraction of 12 may also originate from an initial displacement of bromine giving 5-[(2-aminoethyl)thio]-1-methyl-2-nitroimidazole 14, although this cannot be observed due to a rapid further displacement of its nitro group. The bromonitroimidazoles 5 and 6 were reduced to 4-bromo-2-amino-1-methylimidazole 25 and 5-bromo-2-amino-1-methylimidazole 26 with Zn/HCl. On reflux in water, in the presence or absence of cysteamine hydrochloride, these undergo a protodebromination resulting in the same product, 2-amino-1-methylimidazole 17. In D2O the 4-bromo isomer was demonstrated to react specifically to give 2-amino-4-deuterio-1-methylimidazole 27. Attempted preparation of the bromoaminoimidazoles 25 and 26 by bromination of 2-amino-1-methylimidazole in water resulted in the clean formation of cis and trans 2-amino-4,5-dihydro-4,5-di-hydroxyimidazolium ions 18.

Darstellung und Charakterisierung von Kupfer(II)-Derivaten des Glycyll-β-alanins und des β-Alanylglycins. Kristallstruktur von Cu(II)-ßAlaGly • H2O / Preparation and Characterization of Copper(II) Derivatives of Glycyl-β-alanine and β-Alanylglycine. Crystal Structure of Cu(II)-β-AlaGly • H2O

Aquacopper(II) glycyl-β-alaninate (1) and aquacopper(II)-β-alanylglycinate (2) were obtained from CuCO3 and the appropriate dipeptide under reflux in water. 2 crystallizes in the orthorhombic space group Pna2I. The lattice constants (291 K) are: a = 8.984(2), b = 12.456(2), c = 6.978(2) Å. The dipeptide anion, acting as a tridentate ONN ligand, and one oxygen atom of the carboxylate group of a neighbouring molecule form the base of a square pyramid around Cu, with water in the apical position. Cu is found slightly above the base. The molecules are connected by bridging carboxylate groups to form chains which are linked by hydrogen bonds between the water molecule and the oxygen atom of the peptide group.

ChemInform Abstract: Selective Dehydrogenation of Ethanol to Acetaldehyde Over Silicalite‐1.

Abstract Silicalite-1 catalyzes ethanol dehydrogenation to acetaldehyde. On the basis of the IR spectra of ethanol adsorbed on its surface, the active sites are believed to be the active oxygen bridges on which dissociative adsorption of ethanol can take place. The active sites are stable compared with the active oxygen bridges on highly dehydrated silica, which also catalyze the selective ethanol dehydrogenation. Since there were trace amounts of acid site on the Silicalite-1, simultaneous ethanol dehydration was observed. However, almost all the acid sites disappeared by heating at 1070 K in the case of Silicalite-1 containing 0.7 wt% of sodium ions, and ethanol was selectively converted to acetaldehyde. In this treatment, the sodium ions partly poison the active sites for dehydrogenation, but their activity is restored by leaching excess sodium ions from the silicalite-1 under reflux in water.

Selective dehydrogenation of ethanol to acetaldehyde over silicalite-1

Silicalite-1 catalyzes ethanol dehydrogenation to acetaldehyde. On the basis of the IR spectra of ethanol adsorbed on its surface, the active sites are believed to be the active oxygen bridges on which dissociative adsorption of ethanol can take place. The active sites are stable compared with the active oxygen bridges on highly dehydrated silica, which also catalyze the selective ethanol dehydrogenation. Since there were trace amounts of acid site on the Silicalite-1, simultaneous ethanol dehydration was observed. However, almost all the acid sites disappeared by heating at 1070 K in the case of Silicalite-1 containing 0.7 wt% of sodium ions, and ethanol was selectively converted to acetaldehyde. In this treatment, the sodium ions partly poison the active sites for dehydrogenation, but their activity is restored by leaching excess sodium ions from the silicalite-1 under reflux in water.

木香中のセスキテルペンの煎出中における挙動

The changes of contents of dehydrocostuslactone (I) and costunolide (II) in the extract of Saussureae Radix were investigated during decoction. The contents of I and II in infused solution were reached to maximum after about 10min of the decoction, respectively. However, when the decoction was continued until the volume becomes to half, the contents of I and II in the solution decreased significantly compared to maximum content in the decoction. The content of II also decreased rapidly during the reflux in water. These results indicated that these small availabilities cause not only by volatilization but also by decomposition.