Revealing the Active Species for Aerobic Alcohol Oxidation by Using Uniform Supported Palladium Catalysts

The active species in supported metal catalysts are elusive to identify, and large quantities of inert species can cause significant waste. Herein, using a stoichiometrically precise synthetic method, we prepare atomically dispersed palladium–cerium oxide (Pd₁/CeO₂) and hexapalladium cluster–cerium oxide (Pd₆/CeO₂), as confirmed by spherical‐aberration‐corrected transmission electron microscopy and X‐ray absorption fine structure spectroscopy. For aerobic alcohol oxidation, Pd₁/CeO₂ shows extremely high catalytic activity with a TOF of 6739 h^?1 and satisfactory selectivity (almost 100 % for benzaldehyde), while Pd₆/CeO₂ is inactive, indicating that the true active species are single Pd atoms. Theoretical simulations reveal that the bulkier Pd₆ clusters hinder the interactions between hydroxy groups and the CeO₂ surface, thus suppressing synergy of Pd‐Ce perimeter.     

C−C Coupling of Benzyl Fluorides Catalyzed by an Electrophilic Phosphonium Cation

The activation and cleavage of benzyl fluorides by the electrophilic organofluorophosphonium catalyst, [(C₆F₅)₃PF][B(C₆F₅)₄], is reported and used for the preparation of 1,1‐diarylalkanes (37 examples) and substituted aryl homoallylic alkenes (14 examples). This procedure involves mild conditions, avoids harmful waste, and is compatible with a range of substituted arenes and allylic silanes.     

Kinetics of Heterogeneous Solvent‐free Liquid Phase Oxidation of Alcohol Using ZrO2 Catalyst with Molecular Oxygen

Clean liquid phase solvent‐free oxidation of alcohol to aldehyde/ketone using ZrO₂ catalyst with molecular oxygen has been studied. Monoclinic phase ZrO₂ has been synthesized and characterized by XRD, SEM, EDX and surface and pore size analyses. Oxidation of alcohol was carried out in a typical batch reactor at different speed of agitation (150–1200 r/min), temperature (373–413 K), catalyst loading (50–300 mg) and partial pressure of oxygen (12–101 kPa). These parameters influence alcohol conversion as well as selectivity. A handy touch of kinetics was given to the experimental data and apparent activation energy was calculated.     

槲皮素-3’-氨基酸酯盐酸盐的合成工艺研究

槲皮素(Quercetin,3,5,7,3,4,-pentahydroxy flavanone)是一种普遍存在于食用或药用植物中的具有广泛生理活性的生物黄酮类化合物,广泛分布于食用和药用植物如洋葱、茶叶、银杏等中[1].     

Novel biomimetic composite based on collagen and poly(γ‐benzyl L‐glutamate)‐co‐poly(glutamic acid)

Novel biomimetic composite was prepared by the reaction of collagen and poly(γ‐benzyl L ‐glutamate)‐co‐poly(glutamic acid) (PBLG‐co‐PGA), which were crosslinked by non‐toxic crosslinking reagents 1‐ethyl‐(dimethylaminopropyl) carbodiimide (EDC) and N‐hydroxysuccinimide (NHS). The composite was characterized by FTIR and DSC. FTIR results confirmed that the collagen in the composite was successfully crosslinked with PBLG‐co‐PGA. DSC results showed that the composites possessed higher shrinkage temperature and higher thermal stability than the collagen. The water absorption test showed that the water absorbency of the composites increased with the increase in PBLG‐co‐PGA content in the composite. The studies of collagenase degradation and the tensile strength showed that the biostability and the tensile strength of the composites were significantly improved in comparison with that of the collagen. According to the investigations of cell adherent ratio and cell proliferation in vitro, the composite possessed good biocompatibility. Copyright © 2007 John Wiley & Sons, Ltd.     

Performance of dodecyl dimethyl benzyl ammonium chloride as bactericide and corrosion inhibitor for 7B04 aluminum alloy in an aircraft fuel system

In this study, the broad-spectrum antimicrobial property of dodecyl dimethyl benzyl ammonium chloride (DDBAC) was investigated against three species of bacteria, Lysinibacillus sphaericus (L. sphaericus), Acinetobacter lwoffii (A. lwoffii), and Sediminibacterium salmoneum (S. salmoneum) isolated and purified from a naval aircraft fuel system. Through the inhibition zone method and minimum inhibitory concentration test, DDBAC was found to have a good antimicrobial performance with a minimum inhibitory concentration of 64 mg/L. The influence of DDBAC on the corrosion behavior of fuel tank material was evaluated by electrochemical measurements, such as polarization curve and electrochemical impedance spectroscopy (EIS). The polarization curve indicated that DDBAC suppressed anodic and cathodic reactions as a mixed-type corrosion inhibitor, and the inhibition efficiency was 68.38% at the concentration of 80 mg/L after 28 days of immersion. The EIS results showed that DDBAC inhibited the corrosion of 7B04 aluminum alloy in the concentration range of 40–120 mg/L. The DDBAC adsorption on the aluminum alloy surface was in agreement with the modified Langmuir adsorption isotherm model. The quantum chemical calculations proved that a lone pair of electrons of nitrogen atoms in DDBAC were able to form coordinate bonds with the empty orbital in aluminum, resulting in a tight chemisorption layer on the aluminum alloy surface and corrosion inhibition.     

Synthesis and Characterization of Benzylidene Bis-Dithiobenzoate

Benzal chloride reacts with sodium sulfide in alcoholic solution to yield three main products: benzyl disulfide, benzyl dithiobenzoate, and a new interesting compound 5 , C ₂₁ H ₁₆ S ₄ , which was isolated and characterized as benzylidene bis-dithiobenzoate. The intermediates obtained from the autoxidation-reduction of the unisolable thiobenzaldehyde are implied in subsequent nucleophilic addition and substitution processes. NMR spectra and X-Ray structure analysis of 5 are discussed.     

An Improved Synthesis and Isolation of Tribenzylbismuth

A much improved synthesis and isolation of tribenzylbismuth (Bn₃Bi where Bn = CH ₂ C ₆ H ₅ ) compared to the previous literature preparation is presented. Using the described method, a ≥ 3-fold increase in yield of analytically pure compound is obtained, providing Bn ₃ Bi in synthetically useful quantities. Additionally, full spectral characterization has been achieved ( ¹ H and ¹³ C NMR, IR) for the first time. Thermal analysis was performed via condensed phase pyrolysis and differential scanning calorimetry (DSC). The DSC data was used to estimate Δ H _f (Bn ₃ Bi) _liquid .     

Fluorescent,thermoresponsive copolymers via nitroxide‐mediated polymerization: Synthesis and effect of fluorescent groups on phase transitions in an ionic liquid

Synthesis of poly(benzyl methacrylate) (PBzMA) by nitroxide‐mediated polymerization with a small fraction of fluorescent, controlling comonomer, 9‐(4‐vinylbenzyl)‐9H‐carbazole (VBK, 2–11 mol % in the feed), was studied along with the resulting copolymers' LCST phase behavior in the ionic liquid (IL) 1‐ethyl‐3‐methylimidazolium bis(trifluoromethane sulfone)imide. The effectiveness of VBK as a controlling comonomer was demonstrated by a dramatic decrease in the product of average propagation rate constant and average equilibrium constant, <k_p><K>, compared to BzMA polymerizations with styrene as comonomer. Linear molecular weight increase with conversion (up to ～40% conversion), with polydispersities of about 1.34–1.42, and successful chain extensions indicated the copolymerizations were relatively well controlled. The incorporation of fluorescent and solvatophobic VBK units in the BzMA/VBK copolymers not only affected transition temperature and reversibility of the LCST‐type phase separation in the IL, but also led to about a fivefold phase separation‐triggered fluorescent enhancements, likely due to enhanced fluorescence resonance energy transfer from BzMA to VBK being in close proximity during aggregation. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4702–4715