Preparation and Curing of Poly (Perfluoroalkylene Oxides)†

Abstract

A series of functionally terminated poly(perfluoroalkylene oxides), a new class of curable, liquid, fluorinated polymers, has been prepared by the photopolymerization of perfluorooxydipropionyl fluoride, O(CF₂CF₂COF)₂, and related perfluoroacyl fluoride monomers. Polymerization proceeds by ultraviolet-induced scission of CF₂COF groups and coupling of the CF₂—radicals thus formed. Polymer molecular weight and functionality increase with photolysis time. The acid fluoride-terminated polymers (Mn 1000–5000, functionality 2–5) are liquids possessing low T_g (about ?60°C) and excellent, thermal stability. Other functional end groups (e.g., COOH, COOR, CH₂OH, etc.) have been prepared using standard reactions.     

A Concise and Convenient Synthesis of Stilbenes via Benzils and Arylmethyldiphenylphosphine Oxides

A new and convenient synthetic method has been developed for the construction of stilbenes bearing electron-withdrawing group（s） by using benzils and arylmethyldiphenylphosphine oxides via sequences involving Wittig-Horner reaction and a rearrangement in the presence of t-BuOK in toluene under mild conditions. This approach could be readily applied to a facile synthesis of biologically important natural products, resveratrol and its derivatives, such as trimethoxystilbenes 1 （Z） and 2 （E）.     

Nickel-Catalyzed Asymmetric Hydrogenation of α-Substituted Vinylphosphonates and Diarylvinylphosphine Oxides

Chiral α-substituted ethylphosphonate and ethylphosphine oxide compounds are widely used in drugs, pesticides, and ligands. However, their catalytic asymmetric synthesis is still rare. Of the only asymmetric hydrogenation methods available at present, all cases use rare metal catalysts. Herein, we report an efficient earth-abundant transition-metal nickel catalyzed asymmetric hydrogenation affording the corresponding chiral ethylphosphine products with up to 99 % yield, 96 % ee (enantiomeric excess) (99 % ee, after recrystallization) and 1000 S/C (substrate/catalyst); this is also the first study on the asymmetric hydrogenation of terminal olefins using a nickel catalyst under a hydrogen atmosphere. The catalytic mechanism was investigated via deuterium-labelling experiments and calculations which indicate that the two added hydrogen atoms of the products come from hydrogen gas. Additionally, it is believed that the reaction involves a Ni^II rather than Ni⁰ cyclic process based on the weak attractive interactions between the Ni catalyst and terminal olefin substrate.     

Mössbauer Spectroscopy of Iron Oxides and Related Compounds

The superparamagnetic iron oxide particles with a diameter of about 10 and 16 nm were obtained by the reaction of Fe²⁺ and Fe³⁺ ions in a water pool of reversed microemulsions. The obtained particles were ascribed to -Fe₂O₃ due to the oxidation of Fe₃O₄. Very fine particles of -Fe and Fe₃O₄ were also obtained by the thermal decomposition of FeC₂O₄2H₂O. The decomposition products and their particle size depended on the heat treatments.     

An XPS Study of Perovskite Oxides

An　XPS　Study　of　Perovskite　Oxides　...     

Surface and Catalytic Properties of TiO2–ZrO2 Mixed Oxides

This paper reviews acid–base bifunctional catalysis and surface properties (morphology, composition, specific area, acidity/basicity, site density) on TiO₂–ZrO₂ (abbreviated as TZ) mixed oxides. The phase change from crystalline single oxides (TiO₂ and ZrO₂) to amorphous TZ mixed oxide results in decreasing grain size and site density, increasing surface area, acid/base amount and strength, and better activity/selectivity. Different acid–base bifunctional mechanisms (concerted, go-together, stepwise) were proposed to interpret the reaction behavior of various reactions (esterification, dehydration, dehydrogenation, isomerization, dehydrocyclization) over the acid–base bifunctional TZ catalysts.     

Synthesis and Characterization of Organoboryl Germanium (Ⅱ) Oxides Containing Ge-O-B and Ge-O-B-O-Ge Cores

Organoboryl germanium(Ⅱ) oxides were synthesized from the 1,4-addition reaction of L'Ge(L'=HC[C(CH_2)N(Ar)]C(Me)N(Ar),Ar=2,6-iPr_2C_6H_3) with selected monosubstituted arylboronic acids RB(OH)_2(R=2,6-Me_2C_6H_3,2,4,6-Me_3C_6H_2,1-Naph) at the molar ratios of 1:1 and 2:1.The mononuclear products RB(OH)OGeL(L=CH[C(Me)N(Ar)]_2,Ar=2,6-iPr_2C_6H_3;R=2,6-Me_2C_6H_3(1),2,4,6-Me_3C_6H_2(2),1-Naph(3)) containing the Ge-O-B core were obtained smoothly through the 1:1 reaction.However,the reaction of L'Ge with 2,6-Me_2C_6H_3B(OH)_2 in a 2:1 ratio gave only the mononuclear product(1) instead of the expected binuclear one.What's more,a new borate compound [(2,6-Me_2C_6H_3)_4B_5O_6]~-[H:C]~+(4)(:C=C[N(iPr)C(Me)]_2) was concomitantly formed when the in situ prepared L'Ge was used as the precursor.In contrast,the use of 2,4,6-Me_3C_6H_2B(OH)_2 or1-NaphB(OH)_2 as the organoboryl source in the similar reaction led to the formation and isolation of the binuclear products RB(OGeL)2(R=2,4,6-Me_3C_6H_2(5),1-Naph(6)) containing the Ge-O-B-O-Ge core in a straight way.Compounds 1~6 were determined by single-crystal X-ray diffraction analysis.     

The Electronic Structures and Catalytic Activities of Triruthenium Ketenylidene Clusters Supported on Oxides

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Electrosynthesis of Zirconium Boride from Cryolite–Alumina Melts Containing Zirconium and Boron Oxides

Electrosynthesis of zirconium boride from cryolite–alumina melts containing zirconium and boron oxides is studied. A thermodynamic estimate of the synthesis feasibility and cyclic voltammetry data prove that the synthesis involves one stage. Electrolytic ZrB₂coatings on nickel are obtained.     

Structural Modulation of Manganese Oxides for Zinc-ion Batteries

1 PROSPECTS FOR MnO2-BASED AQUEOUS Zn-ION BATTERY Aqueous rechargeable zinc-ion batteries(AZIBs)have been considered as promising alternatives to lithium-ion batteries for electrochemical energy storage.There are two typical overwhelming advantages that make AZIBs stand out among the various electrochemical energy storage systems(organic alkaline ion batteries,e.g.,Na^+and K^+,and aqueous batteries,e.g.,Na^+,K^+,Mg^2+,and Al^3+).Firstly,some advantages come from the utilization of aqueous electrolyte.The aqueous electrolytes could deliver 2 orders of magnitude higher ionic conductivities(~1 S cm^-1)than the non-aqueous electrolytes(~1-10 mS cm^-1)[1].Moreover,aqueous electrolyte reduces the fabrication cost comparing with the usage of organic solvents.In addition,it is an important point that the high operational safety and environmental friendliness derived from aqueous electrolyte endows AZIBs with strong competitiveness.Secondly,zinc metal can directly be used as the anode in the AZIBs,which makes the AZIBs more promising than other aqueous batteries(Al^3+,Mg^2+,Na^+,K^+).Zn anode features the low oxidation-reduction potential of Zn^2+/Zn(-0.76 V vs.standard 2H^+/H2 potential),which can deliver higher energy density[2].Moreover,the low-cost Zn metal can decrease the manufacturing cost.     

Surface Charge of Silver Iodide and Several Metal Oxides. Are All Surfaces Nernstian?

Charge titration data for silver iodide, titanium dioxide, aluminum oxide, silica dioxide and ferric hydroxide are analyzed using a generic site binding model that has the Nernst equation as a limiting form. Both the hypernetted chain and the nonlinear Poisson-Boltzmann approximations are used to relate the diffuse double-layer potential to the surface charge, and a zeroth-order Stern layer is used to give the surface potential. In all cases it is shown that in the vicinity of the point of zero charge the Nernst equation accurately gives the surface charge. Copyright 2000 Academic Press.     

Properties of NiO–ThO2 Mixed Oxides From Hydroxides and Their Hydrogen Reducibility Behaviour

Some physico-chemical properties of NiO–ThO₂ mixed oxides of various compositions have been investigated. The presence of strongly bound constitutional water in the hydrogel of reactive forms of thorium dioxide, determined by their origin (thermal decomposition of mixed hydroxides) caused the different reduction behaviour as compared with other mixed oxide systems containing the only, thermodynamically less stabile reducible component. The significant effects of the thermal treatment in oxygen atmosphere, pre-irradiation by the gamma rays or accelerated electrons under various conditions (in air or in water suspension) as well as of surface chemical activation with a platinum complex on the reactivity of mixed oxides or reoxidized samples during their hydrogen reduction have been also proved. This revised version was published online in August 2006 with corrections to the Cover Date.     

Catalytic Dehydration of α-Phenylethanol on the Surface of Aluminum Oxides

The relationship between the acid–base properties of commercial and test samples of aluminum oxides and their catalytic activity in the dehydration of -phenylethanol was studied. It was found that, in the dehydration of -phenylethanol, the conversion of the alcohol and the yield of styrene on a catalyst depend on the concentrations of both Brønsted and Lewis acid sites. A hypothetical mechanism of the dehydration with the participation of coordinatively unsaturated aluminum atoms and bridging oxygen ions on the alumina surface was proposed.     

Aerobic Oxidation of Benzyl Alcohol Catalyzed by Cu-Mn Mixed Oxides and 2,2,6,6-Tetramethyl-piperidyl-1-oxyl

Heterogeneous Cu-Mn mixed oxides can mediate TEMPO-catalyzed selective oxidation of benzyl alcohol by molecular oxygen under neutral condition, and is recyclable. In the case of the molar ratio of Cu and Mn over 1, the highly-dispersed CuO inside the Cu-Mn mixed oxides is responsible for the good performances in catalytic oxidation.     

Synthesis and Solvolysis of [(ω-(Dimethylphenoxysilyl)alkyl]-diphenylphosphines,Phosphine Oxides and Phosphine Sulfides

Abstract

Kinetics of base catalysed solvolytic cleavage of phenoxy group from compounds of general structure X (CH₂)nSiMe₂OPh, where n=1,2,3 and X=Me,Ph₂P, Ph₂P (p), Ph₂P(s) has been investigated. The main purpose was to study the effect of phosphorus groups on the reactivity in substitution reaction at silicon. We wanted to answer the question whether there is any direct interaction of the phosphorus groups with silicon moiety, modifying this reactivity. Complementary NMR studies have also been performed for this purpose.     

Effect of Amines on the Surface Charge Properties of Iron Oxides

Specific studies detailing the effects of amines, used as pH control agents for corrosion inhibition in power plants, on the surface charge of iron oxides provide data to assess the mechanism of how these amines impact deposition rate. The current study was undertaken in order to determine accurately the dissociation constants of the relevant amines at Pressurized Water Reactor (PWR) operating conditions and to investigate the effect of sorption of two of these amines (morpholine and dimethylamine) by magnetite. The acid-dissociation equilibria of morpholine (MOR), dimethylamine (DMA) and ethanolamine (ETA) were measured potentiometrically with a hydrogen-electrode concentration cell (HECC) from 0 to 290 °C in sodium trifluoromethanesulfonate (NaTr) solutions at ionic strengths up to 1 mol⋅kg⁻¹. Magnetite surface titrations were performed at an ionic strength of 0.03 mol⋅kg⁻¹ (NaTr medium) in the presence or absence of morpholine and dimethylamine buffers over a wide range of pH and total amine concentrations at 150–250 °C. D.A. Palmer is retired.     

Aerobic Oxidation of Benzyl Alcohol Catalyzed by Cu-Mn Mixed Oxides and 2,2,6,6-Tetramethyl-piperidyl- 1-oxy1

Heterogeneous Cu-Mn mixed oxides can mediate TEMPO-catalyzed selective oxidation of benzyl alcohol by molecular oxygen under neutral condition, and is recyclable. In the case of the molar ratio of Cu and Mn over 1, the highly-dispersed CuO inside the Cu-Mn mixed oxides is responsible for the good performances in catalytic oxidation.     

The Reaction of α-Amino-Substituted Diphenylphosphine Oxides with Elemental Sulfur and Selenium. A New Route to Thio- and Selenoamides

Abstract

Lithiated α-amino-substituted diphenylphosphine oxides 1 showed an interesting reactivity towards sulfur and selenium, leading to the formation of thioamides 2 and selenoamides 3, which could be isolated in good yields. Two equivalents of the chalcogene were found to be needed for complete conversion of the phosphine oxide anions. In the case of sulfur, diphenylphosphinothioic acid 4 was isolated as a side product, thus explaining the stoichiometry of the reaction (Scheme 1).     

Studies on Oxidative Coupling of Methane Catalysed by Li-Ce-Sr Oxides

The conditions for catalyst preparation and coupling reaction of methane were investigated. The experimental results showed that under the catalysts the selectivity for C2 formation may reach 98.5% and the yield 28.2% (the average within the first 30 minutes). A stale selectivity and yield for C2 formation obtained after reaction for 2h were 48.4% and 20.6%, respectively. Some kinetic parameters were also determined, including activation energy and the partial pressure dependence of the catalytic reaction rates. Finally a preliminary explanation of the reaction mechanism is suggested.     

Hypervalent Iodine–Catalyzed Cycloaddition of Nitrile Oxides to Alkenes

A new and convenient method for preparation of isoxazolines was developed by a catalytic cycloaddition of nitrile oxides generated in situ from aldoximes to alkenes in the presence of a catalytic amount of iodobenzene. In this protocol, iodobenzene was first oxidized into the hypervalent iodine intermediate by m-chloroperbenzoic acid, which then transformed aldoximes into nitrile oxides, and a 1,3-dipolar cycloaddition of nitrile oxides to alkenes to provide the isoxazolines in moderate to good yields.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.]