Influence of the method of synthesis on the composition and structure of copper(II) complexes with galactaric acid

The influence of the conditions and the method of synthesis on the composition of copper(II) complexes with galactaric acid (H₂Gala) has been studied. In aqueous and water-DMSO solutions, 1 : 1 complexes are formed. Depending on the procedure and conditions of the synthesis, CuGala · 4H₂O, Cu(HGala)₂ · 4H₂O, and (CuOH)₂Gala · 2H₂O compounds have been obtained. The structure of the coordination environment of the metal ion has been identified by IR spectroscopy.     

Loading of g-C3N4 on Core-Shell Magnetic Mesoporous Silica Nanospheres as a Solid Base Catalyst for the Green Synthesis of some Chromene Derivatives under Different Conditions

Using heterogeneous basic catalysts has a great importance in chemical reactions because of their advantages (such as easy separation and thermal stability at harsh conditions) over homogeneous catalysts. In this study, magnetic mesoporous silica nanoparticles (mSiO₂) containing graphitic carbon nitride layers (mSiO₂/g-C₃N₄(x)) were fabricated through a facile process (x signifies the amount of melamine applied during synthesis). Graphitic carbon nitride layers were decorated on mSiO₂ by calcination of immobilized melamine (as graphitic carbon nitride precursor) on mSiO₂ in the last step of catalyst synthesis. The structure of the prepared catalysts was confirmed using XRD, BET, FESEM, EDX, elemental mapping and TEM methods. The catalytic efficiency of the so-obtained solid base composite was investigated for the synthesis of some dihydropyranochromenes and spiro-dihydropyranochromenes under thermal and microwave conditions. Using mSiO₂/g-C₃N₄(x) led to high yields under green conditions and in short reaction times and without a decrease in catalytic activity after four consecutive cycles.     

Effect of Synthesis Method on the Phase Composition and Ion-Exchange Properties of Titanium Phosphate

Relationships between synthesis conditions, phase composition, and ion-exchange properties have been analyzed on the basis of results of physicochemical study for reaction products in the (NH₄)₂TiO(SO₄)₂–H₃PO₄–H₂O system. Mechanisms have been suggested for the formation of final titanium phosphate phase in different synthesis methods.     

Synthesis of meso-tetraarylporphyrins using SeO2 as oxidant

The oxidative step of the two-step, one-flask synthesis of meso-tetraarylporphyrins is herein conducted with heterogeneous oxidant SeO₂ instead of the usual quinones DDQ or p-chloranil. Evaluation of BF₃O(Et)₂ or I₂ amount for the condensation of the first step combined with the excess of SeO₂ defined porphyrin synthesis conditions employing benzaldehydes and pyrrole (or 5-phenyldipyrromethane) as starting materials. The simplicity of the workup, allied with reaction mild conditions, makes this method a good option for the synthesis of this kind of compound.     

Synthesis of ceria nanosheets on the surface of Ce(NO3)3 solution by interaction with gaseous ammonia

The surfactant-free synthesis of a solid film of ceria was carried out at the air–water interface from an aqueous solution of Ce(NO₃)₃ and gaseous NH₃ as reactants. The synthesized CeO_2?x ? n H₂O film consists of 2D nanocrystals with a fluorite structure. The film can form a planar coating on the surface of a solid substrate or transform into curved fragments upon drying, depending on the synthesis conditions.     

Direct Electrochemical Synthesis of Diaziridines

The possibility of direct electrosynthesis of mono- and bicyclic diaziridines is studied using, respectively, 1,2-dimethyldiaziridine and 1,5-diazobicyclo[3,1,0]hexane as an example. In either case the process is realized in a galvanostatic electrolysis in the anodic space of a diaphragm cell and proceeds through intermediate formation of alkylchloramines; other electrosynthesis conditions depend on the structure of the source aminoalkane. In the synthesis of monocyclic diaziridines, for the electrolyte, a 4 M solution of NaCl in water was used, which contained high concentrations of 0.5 and 2.0 M of, respectively, CH₂O and MeNH₂, and the amine excess served, in particular, for binding protons in the reaction of diaziridine synthesis. The process occurs in a homogeneous phase, and the current efficiency for 1,2-dimethyldiaziridine amounted to 40–50% in optimum conditions. In the synthesis of bicyclic diaziridines, the electrolyte was a 4 M solution of NaCl in a 20-% aqueous methanol, containing a low—0.1 M concentration of H₂N(CH₂)₃NH₂ and an equimolar quantity of CH₂O, and additives of NaHCO₃ were used for binding protons in the reaction of diaziridine synthesis. The process occurs in a heterophase environment because of an incomplete dissolution in the conditions of experiment of NaCl and intermediately-formed chloraminoalkane. The current efficiency for 1,5-diazobicyclo[3,1,0]hexane reached 80–85% in optimum conditions, but the loads of the source aminoalkane were 20 times lower than in the synthesis of monocyclic diaziridines. Compared are the results of a direct and an earlier-described indirect method of electrosynthesis of mono- and bicyclic diaziridines.     

Comparative use of solvent‐free KF‐A12O3 and K2CO3 in acetone in the synthesis of quinoxaline 1,4‐dioxide derivatives designed as antimalarial drug candidates

In this paper we describe two new basic conditions for the synthesis of quinoxaline 1,4‐dioxide derivatives in moderate to good yields. These conditions, exemplified by the use of K₂C0₃ in acetone or KF/A1₂0₃ in the absence of an organic solvent, were reproducible and applicable to the synthesis of 2‐(carboethoxy)‐3‐phenylquinoxaline 1,4‐dioxide derivatives substituted in position 4 with electron‐donating or electron‐withdrawing groups.     

Solid-phase synthesis of sodium-bismuth tungstate NaBi(WO<Subscript>4</Subscript>)<Subscript>2</Subscript>

Results of a solid-phase synthesis of polycrystalline sodium-bismuth tungstate NaBi(WO₄)₂ from NaNO₃, Na₂WO₄, Bi₂O₃, and WO₃ are presented. The optimal synthesis conditions are determined and a technological flow chart for synthesis of a single-phase product is suggested.     

Study of the interaction in the ZnS (ZnO)-Dy2S3 system

The exchange reactions of the impurity ZnO in zinc sulfide produced by self-propagating high-temperature synthesis with the additive Dy₂S₃ were studied by IR spectroscopy and diffuse reflectance electron spectroscopy. It was found that the main products of the interaction in the ZnS (ZnO)-Dy₂S₃ system are ZnS and Dy₂O₂S. The exchange character of the interaction was modeled by the systems ZnO-Dy₂S₃ (2: 1) and Dy₂S₃-Dy₂O₃ (1: 2). The possibility of estimating the ZnO impurity content of zinc sulfide was demonstrated, which allows one to optimize the zinc sulfide synthesis conditions.     

Synthetic studies directed toward the total synthesis of dolabriferol

Herein we report our results towards the total synthesis of (−)-dolabriferol, describing the synthesis of fragments C1-C9 and C10-C21. This convergent asymmetric approach relies on the use of a common Weinreb amide precursor for the preparation of both fragments, an efficient anti-aldol reaction followed by Zn(BH₄)₂ reduction to give a 1,3-syn diol, a selective oxidation of a triol under Swern conditions with concomitant lactol formation, and a diastereoselective epoxidation of an allylic alcohol with m-CPBA followed by an efficient epoxide opening with Me₂CuCNLi₂.     

Influence of the conditions of the sulfate method on the characteristics of nanosized anatase-type samples

The nanosized anatase modification of titanium dioxide was prepared from two forms of solvated titanyl sulfate (TiOSO₄·2H₂O and TiOSO₄·xH₂SO₄·yH₂O) at different initial concentrations of the reagent under different conditions of the hydrolysis and coagulation. The sample characteristics (the sizes of aggregates, microparticles, nanoparticles, and coherent scattering regions, the specific surface area, the nano- and ultrananopore volumes) were deter-mined by scanning electron microscopy, small-angle and wide-angle X-ray diffraction, and physical adsorption of nitrogen at ?196 °C. The relationship between these characteristics and the conditions of the sample preparation was established. The optimal processing conditions were found for the synthesis of samples with a high practical yield of the anatase-type phase.     

Ethylene production by the oxidative condensation of methane in the presence of MnMW/SiO<Subscript>2</Subscript> catalysts (M = Na,K, and Rb)

The samples of MnMW/SiO₂ (M = Na, K, and Rb) were synthesized using various synthesis methods under varied heat treatment conditions and their physicochemical properties and activity in the reaction of the oxidative condensation of methane (OCM) were studied for the development of an effective catalyst for the resource-saving process of natural gas conversion into ethylene. It was found that the preparation method exerts an effect on the textural characteristics of the samples and the reducing properties of the cations of manganese and tungsten. It was determined that the composition of a W-containing phase depends on the alkali metal, and a ratio between the polymorphous modifications of SiO₂ is controlled by the method of synthesis and the conditions of catalyst heat treatment. It was established that the yield of C₂ hydrocarbons in the OCM reaction increased with the use of incipient wetness impregnation instead of the method of mixing with a suspension for catalyst preparation and with an increase in the catalyst heat treatment temperature from 700 to 1000°C. The optimum composition of the catalyst and the condition of its synthesis were found: 2Mn_0.8Na₃W/SiO₂ obtained by the impregnation method and calcined at 1000°C ensured the yield of target products of ~20% with a CH₄ conversion of ~35% at a reaction temperature of 850°C.     

Synthesis of highly branched perfluoroethers by direct fluorination,promising new materials based on the hexafluoroacetone–ethylene copolymer

Direct fluorination of the hexafluoroacetone-ethylene copolymer, [CH₂CH₂OC(CF₃)₂]_n, under conditions designed to promote fragmentation of the polymer chain has led to the synthesis of a number of structurally unusual branched perfluoropolyethers [? CF₂? CF₂? O-C(CF₃)₂? ]_n. These new perfluoropolyethers have been characterized by ¹⁹F-NMR, and their physical properties are reported. Direct fluorination under milder conditions yields a high-molecular-weight perfluoropolyether.     

Calculation of partial molar volume of components in supercritical ammonia synthesis system

The partial molar volumes of components in supercritical ammonia synthesis system are calculated in detail by the calculation formula of partial molar volume derived from the R-K equation of state under different conditions. The objectives are to comprehend phase behavior of components and to provide the theoretic explanation and guidance for probing novel processes of ammonia synthesis under supercritical conditions. The conditions of calculation are H₂/N₂ = 3, at a concentration of NH₃ in synthesis gas ranging from 2% to 15%, concentration of medium in supercritical ammonia synthesis system ranging from 20% to 50%, temperature ranging from 243 K to 699 K and pressure ranging from 0.1 MPa to 187 MPa. The results show that the ammonia synthesis system can reach supercritical state by adding a suitable supercritical medium and then controlling the reaction conditions. It is helpful for the supercritical ammonia synthesis that medium reaches supercritical state under the conditions of the corresponding total pressure and components near the normal temperature or near the critical temperature of medium or in the range of temperature of industrialized ammonia synthesis. __________ Translated from Journal of Chemical Industry and Engineering, 57(7):1503–1507 [译自: 化工学报]     

Synthesis of peroxy-radical condensates from mixtures of H<Subscript>2</Subscript>+O<Subscript>2</Subscript>

One of the methods for the synthesis of peroxy-radical condensates is the condensation at liquid nitrogen temperature of an H₂+O₂ mixture dissociated in an electrical discharge at low pressure. Peroxy-radical condensates are thought to contain substantial quantities of higher hydrogen peroxides H₂O₃ and H₂O₄. The present work investigates the influence of experimental parameters on the synthesis of peroxy-radical condensates from an H₂+O₂ mixture, analyses the relevant literature, and recommends the optimal experimental conditions for the synthesis. The synthesis is carried out in a U-tube electrical discharge reactor (inner diameter ∼15 mm), immersed in liquid nitrogen, at rather low pressure (0.5–1 Torr). The maximum conversion of initial O₂ into higher hydrogen peroxides was observed at a composition of initial gas mixture of 66.7% H₂ + 33.3% O₂.     

1,1-Dihydroperoxycyclododecane as a new, crystalline non-hygroscopic oxidizer for the chemical synthesis of oligodeoxyribonucleotides

A new oxidation method for DNA synthesis was developed by the use of 1,1-dihydroperoxycyclododecane in CH₂Cl₂-EtOAc under anhydrous conditions. This new oxidizer was successfully applied to the synthesis of oligodeoxyribonucleotides that involves an oxidation step for conversion of phosphite intermediates to phosphate derivatives.     

Zeolite Synthesis in the Presence of Metallosiloxanes for the Quantitative Encapsulation of Metal Species for the Selective Catalytic Reduction (SCR) of NOx

Metal encapsulation in zeolitic materials through one-pot hydrothermal synthesis (HTS) is an attractive technique to prepare zeolites with a high metal dispersion. Due to its simplicity and the excellent catalytic performance observed for several catalytic systems, this method has gained a great deal of attention over the last few years. While most studies apply synthetic methods involving different organic ligands to stabilize the metal under synthesis conditions, here we report the use of metallosiloxanes as an alternative metal precursor. Metallosiloxanes can be synthesized from simple and cost-affordable chemicals and, when used in combination with zeolite building blocks under standard synthesis conditions, lead to quantitative metal loading and high dispersion. Thanks to the structural analogy of siloxane with TEOS, the synthesis gel stabilizes by forming siloxane bridges that prevent metal precipitation and clustering. When focusing on Fe-encapsulation, we demonstrate that Fe-MFI zeolites obtained by this method exhibit high catalytic activity in the NH₃-mediated selective catalytic reduction (SCR) of NO_x along with a good H₂O/SO₂ tolerance. This synthetic approach opens a new synthetic route for the encapsulation of transition metals within zeolite structures.     

Effects of the Brookite Phase on the Properties of Different Nanostructured TiO2 Phases Photocatalytically Active Towards the Degradation of N-Phenylurea

Different sol-gel synthesis methods were used to obtain four nanostructured mesoporous TiO₂ samples for an efficient photocatalytic degradation of the emerging contaminant N-phenylurea under either simulated solar light (1 Sun) or UV light. Particularly, two TiO₂ samples were obtained by means of as many template-assisted syntheses, whereas other two TiO₂ samples were obtained by a greener template-free procedure, implying acidic conditions and, then, calcination at either 200 °C or 600 °C. In one case, anatase was obtained, whereas in the other three cases mixed crystalline phases were obtained. The four TiO₂ samples were characterized by X-ray powder diffraction (followed by Rietveld analysis); Transmission Electron Microscopy; N₂ adsorption/desorption at −196 °C; Diffuse Reflectance UV/Vis spectroscopy and ζ-potential measurements. A commercial TiO₂ powder (i. e., Degussa P25) was used for comparison. Differences among the synthesized samples were observed not only in their quantitative phase composition, but also in their nanoparticles morphology (shape and size), specific surface area, pore size distribution and pH_IEP (pH at isoelectric point), whereas the samples band-gap did not vary sizably. The samples showed different photocatalytic behavior in terms of N-phenylurea degradation, which are ascribed to their different physico-chemical properties and, especially, to their phase composition, stemming from the different synthesis conditions.     

Synthesis of Silica Aerogels: Influence of the Supercritical CO2 on the Sol-Gel Process

The synthesis of silica aerogels was modified by addition of supercritical CO₂ during the sol-gel process. It was shown, that CO₂ acts as a catalyst and accelerates the gelation significantly. This effect was studied under a multitude of experimental conditions. The influence of the precursor concentration, temperature and the nature of the catalysts and solvent on the gel formation in presence of CO₂ was studied. Several gels obtained by this method were dried and transparent silica aerogels were produced.     

Sequestration of supercritical CO2 by mercury oxide

HgCO₃·2HgO (mercury oxide carbonate), along with partly unreacted reactants, was obtained by exploring the behaviour of the Hg₂Cl₂/HgO binary system in supercritical CO₂ (scCO₂) at 200°C, 22000 kPa in the presence and absence of water, using a self-made laboratory-scale system. The reaction of pure HgO with scCO₂ aimed at the synthesis of HgCO₃ (mercury carbonate), also yielded the same product. Meanwhile, with a small amount of water present in the Hg₂Cl₂/HgO-scCO₂ system, at 200°C, 22000 kPa, the mineral terlinguaite (Hg₄O₂Cl₂) was obtained instead of mercury oxide carbonate. Repeating this reaction under the same conditions, but in the absence of CO₂, again resulted in the synthesis of terlinguaite, leading to the assumption that the scCO₂ had no influence on the synthesis of terlinguaite. This study reveals a new moisture-free laboratory method and conditions for the permanent fixation of CO₂ by HgO. This method bears two benefits: 1) it can be introduced to reduce the Hg content in flue gas and fly ash emitted from coal-burning power plants and municipal waste incinerators; 2) it can contribute to CO₂ mineralisation in montroydite (HgO) geological formations as mercury oxide carbonate.