Abstract Red phosphorus reacts with 4-methoxystyrene in the KOH-DMSO superbase system (130 °C, 3 h, Ar) in the presence of a small quantity of H2O to give tris[2-(4-methoxyphenyl)ethyl]phosphane oxide as the main product in 30% yield. Microwave activation of the reaction (600 W, 6 min) affords basically a mixture of the phosphane oxide and tris[2-(4-methoxyphenyl)ethyl]phosphane (in a ratio of 1:1). When the mixture is exposed to air (r.t., 24 h), the phosphane oxide is formed in 85% yield. GRAPHICAL ABSTRACT 相似文献
Abstract The interaction of the complexes (Et4 N)[Pt(R2 SO)X3] (R = Me, Et, CH2 Ph, X [dbnd] C1; R [dbnd] Me, X [dbnd] Br) and cis-[Pt(Me2 SO)2 Cl2] with concentrated HX (X [dbnd] Cl. Br) results in the reduction of the coordinated sulfoxides and oxidation of Pt(II) to Pt(IV). As a result [Pt(R2 S)X5 and [Pt(R2S)2 X4] are formed. Ligands R2 S can be removed from the complexes and isolated in a free state. 相似文献
Using the thermochemical approach to interpret the kinetics of heterogeneous reactions and the mechanism of congruent dissociative decomposition of solids developed in the 1980s and (re)analyzing the experimental data available in the literature over the last 90 years, a novel mechanism for the catalytic oxidation of H2 by PtO2 is proposed. In place of the conventional Langmuir–Hinshelwood and Eley–Rideal adsorption reaction mechanisms, our model is based on the reactions: PtO2(s) + 2H2 ? Pt(g) + 2H2O and Pt(g) + O2 ? PtO2(g) → PtO2(s). The first reaction determines the kinetics of H2 oxidation and the second determines the kinetics of restoration of the PtO2 layer. Thermochemical consideration of kinetic features of this model enables (for first time in the history of this reaction) the enthalpy and equilibrium constants for H2 oxidation on platinum to be calculated. The results are in good agreement with experimental data. In addition, the proposed mechanism explains the origin of the surface-retexturing effect, the impact of autocatalysis, the influence of H2O vapor on oxidation rate, and the three-fold variation of the Arrhenius E parameter with temperature. This all convincingly demonstrates the value of the thermochemical approach in interpreting heterogeneous reactions. 相似文献
Herein we describe the preparation and structure‐activity relationship studies on range of stilbene based compounds and their antibacterial activity. Two related compounds, each bearing carboxylic acid moieties, exhibit good activity against several bacterial strains, including methicillin‐resistant Staphylococcus aureus MRSA (ATCC 33592 and NCTC 10442). Compound 10 was most active against Moraxella catarrhalis with minimum inhibitory concentrations (MICs) of 0.12–0.25 μg mL?1 and against Staphylococcus spp. with MICs ranging from 2–4 μg mL?1. The derivative 17 showed increased activity with MICs of 0.06–0.25 μg mL?1 against M. catarrhalis and 0.12–1 against Staphylococcus spp. This level of activity is similar to that reported for S. aureus for antibiotics, such as vancomycin, with MICs of ≤2.0 μg mL?1 and clindamycin with MICs of ≤0.5 μg mL?1. As an indicator of toxicity, 17 was tested for its ability to lyse sheep erythrocytes, and showed low haemolytic activity. Such results highlight the value of tris(stilbene) compounds as antibacterial agents providing suitable properties for further development. 相似文献
3-Thia(selena)pentane-1,5-diones react with Lewis acids by heteroatom. In these reactions soft Lewis acids such as tin tetrachloride and antimony pentachloride form adducts but hard Lewis acid such as phosphorus pentachloride oxidizes chalcogen atom of 3-thia(selena)-pentane-1,5-dione. Carbon analogues of these diketones form pyrylium salts in the reactions with these Lewis acids. 相似文献
The 12CO2/13CO2 isotope ratio is a well-known marker in breath for a variety of biochemical processes and enables monitoring, e.g., of the glucose metabolism during sepsis. Using animal models—here, at a mouse intensive care unit—the simultaneous determination of 12CO2 and 13CO2 within small volumes of mouse breath was enabled by coupling a novel low-volume hollow waveguide gas cell to a compact Fourier transform infrared spectrometer combined with multivariate data evaluation based on partial least squares regression along with optimized data preprocessing routines. 相似文献
Secondary phosphine chalcogenides react with diacetone‐d‐glucose (DAG) in the system CCl4/Et3N (70°C, 4–24 h) to afford DAG chalcogenophosphinates in up to 79% yield, thus paving a short way to optically active chalcogenophosphinates with glucose moieties. As an example, a mild regioselective hydrolysis (70°C, aqueous MeCOOH) of DAG bis(2‐phenylethyl)selenophosphinate) obtained leads to monoacetone‐d‐glucose bis(2‐phenylethyl)selenophosphinate. 相似文献
Recently, metasurfaces have received increasing attention due to their ability to locally manipulate the amplitude, phase and polarization of light with high spatial resolution. Transmissive metasurfaces based on high‐index dielectric materials are particularly interesting due to the low intrinsic losses and compatibility with standard industrial processes. Here, it is demonstrated numerically and experimentally that a uniform array of silicon nanodisks can exhibit close‐to‐unity transmission at resonance in the visible spectrum. A single‐layer gradient metasurface utilizing this concept is shown to achieve around 45% transmission into the desired order. These values represent an improvement over existing state‐of‐the‐art, and are the result of simultaneous excitation and mutual interference of magnetic and electric‐dipole resonances in the nanodisks, which enables directional forward scattering with a broad bandwidth. Due to CMOS compatibility and the relative ease of fabrication, this approach is promising for creation of novel flat optical devices.
We describe a method for the synthesis of gold nanoparticles in a stainless steel continuous flow tubular reactor using tetrachloroauric acid as a precursor but without using a classical reducing agent. Gold(III) ion is reduced by stainless steel to form gold nanoparticles which are collected at the end of the coil. A single-phase system is introduced that generates dispersed nanoparticles in the absence of reducing agents on their surface. By controlling flow rates and temperature, the size of the nanoparticles can be tuned in the range from 24 nm to 36 nm. The reproducibility of the preparation was investigated, relative standard deviation of both the wavelength of the peak and the intensity of the plasmonic absorption band were determined and found to vary by 0.15 % and 6.5 %, respectively. Flow synthesis is found to be an excellent alternative to chemical methods to produce stable gold nanoparticles of varying size in an efficiently way. The particles obtained also perform very well when used as a substrate in surface enhanced Raman scattering as shown by the characterization of carboxylated single walled carbon nanotubes.
Figure
Bare gold nanoparticles have been synthesized in a single-phase stainless steel continuous flow tubular reactor using tetrachloroauric acid as a precursor 相似文献