Palladium-catalyzed addition of nitrogen pronucleophiles to alkylidenecyclopropanes

The inter- and intramolecular additions of cyclic amides (nitrogen pronucleophiles) to methylenecyclopropanes proceeded smoothly in the presence of catalytic amounts of Pd(PPh(3))(4), affording the corresponding hydroamination products in good to high yields with high regioselectivities. The ring opening of methylenecyclopropanes occurred at the distal position of the cyclopropane ring.     

Light-induced isotopic exchange between O2 and semiconductor oxides, a characterization method that deserves not to be overlooked

This article first indicates the various types of temperature-induced oxygen isotopic exchange (OIE) that can occur between labeled gaseous O₂ and solid oxides. Earlier main results of light-induced OIE with semiconductor oxides are then briefly reviewed. The core of the article reports new results about the use of light-induced OIE to assess (i) the lability of TiO₂ surface O atoms, as altered by calcination or Se deposits, via the comparison of OIE with the photocatalytic removal of methanol in air and (ii) the accessibility of TiO₂ affixed on a fiberglass material by means of a silica binder. Both this overview and these novel results illustrate the interest of OIE in heterogeneous photocatalysis.     

Paramagnetic charge-transfer guest–host coordination polymers. Thiophene compounds encapsulated within the channels of the three-dimensional coordination polymers [(R3Sn)3Fe(CN)6] n,R = Me,n-Bu or Ph

Various thiophene compounds have been shown to be encapsulated and partly oxidized within the channels of the three-dimensional (3D) host coordination polymers [(R₃Sn)₃Fe(CN)₆] _n (R = Me, n-Bu or Ph) to give guest–host encapsulated systems. The structure and physical properties of these systems were studied by X-ray powder diffraction, i.r., u.v.–vis., e.p.r. spectra and magnetic measurements. Thiophene compounds do not polymerize within the channels of the host, but rather give paramagnetic charge-transfer guest–host systems.     

基于氨基酸的Cu(Ⅱ)-色氨酸MOF催化剂上环氧化物与CO2环加成反应

由天然的/生物单元(氨基酸)构成的金属有机框架材料(MOFs)具有自然属性和丰富的酸/碱位和官能团,因而可用于CO2化学中.本文报道了氨基酸系含铜MOF(CuTrp,Trp = L-色氨酸)的催化效率.以甲醇为溶剂,在室温采用直接混合法合成了CuTrp催化剂,该方法具有很高的能量效率.采用X射线衍射、红外光谱、热重分析、电感耦合等离子体发射光谱法、扫描电镜和BET分析等手段对该催化剂进行了表征.采用环氧化物与CO2环加成制备环状碳酸酯反应评价了CuTrp催化剂活性.结果表明,在无溶剂条件下,CuTrp 催化剂可与四丁基溴化铵助催化剂发生协同作用.通过条件实验确定了优化的反应条件,并基于该实验结果和前期的密度泛函理论计算结果提出了反应机理.另外,CuTrp 催化剂在水中也表现出令人满意的稳定性,可重复使用三次以上而活性无明显下降.     

Indium doped zinc oxide nanopowders for transparent conducting coatings on glass substrates

Crystalline indium doped zinc oxide (IZO) nanopowders were synthesized using hydrothermal treatment processing. Increasing the doping ratio of indium in the zinc oxide significantly influences the phase structure and shape of the nanopowders resulting in nanorod to nanoparticulate morphologies. As the doping profile increases, the crystallite size decreases, the band gap energy blue shifts and the specific surface area increases (measured by BET method). Additionally Raman spectroscopy exhibited shifts of several peaks, as well as revealed new peaks, confirming the substitution of indium ions within the zinc oxide lattice sites. An IZO suspension made of IZO nanoparticles (In/Zn = 3 atm.%) with a zeta potential greater than 30 mV at pH = 6 was successfully spin-coated on glass substrates for to make transparent conductive coatings evincing sheet resistances as low as 35 kΩ_□ (ρ = 4.9 × 10^?3 Ω m,) with transmission in the visible range as high as 90 %.     

Synthesis of 5-azaindolizine derivatives by the palladium-catalyzed intermolecular formal [3+2] cycloaddition of alkylidenecyclopropanes with 1,2-diazines

The palladium-catalyzed formal [3+2] cycloaddition reaction of alkylidenecyclopropanes with 1,2-diazines proceeded smoothly to give the corresponding 5-azaindolizine derivatives in good to allowable yields. For example, in the presence of 5 mol % of Pd(PPh(3))(4), the reaction of 1-propylhexylidenecyclopropane with phthalazine or with pyridazine proceeded at 120 degrees C without solvent, and the corresponding 2-(1-butylpentyl)pyrrolo[2,1-a]phthalazine or 6-(1-butylpentyl)pyrrolo[1,2-b]pyridazine was obtained in 61% or 49% yield, respectively.     

Heavy reflux PSA cycles for CO2 recovery from flue gas: Part I. Performance evaluation

This study evaluated nine stripping PSA cycle configurations, all with a heavy reflux (HR) step, some with a light reflux (LR) step, and some with a recovery (REC) or feed plus recycle (F+R) step, for concentrating CO₂ from stack and flue gas at high temperature (575 K) using a K-promoted HTlc. Under the process conditions studied, the addition of the LR step always resulted in a better process performance; and in all cases, the addition of a REC or F+R step surprisingly did not affect the process performance except at low feed throughputs, where either cycle step resulted in a similar diminished performance. The best cycle based on overall performance was a 5-bed 5-step stripping PSA cycle with LR and HR from countercurrent depressurization (CnD) (98.7% CO₂ purity, 98.7% CO₂ recovery and 5.8 L STP/hr/kg feed throughput). The next best cycle was a 5-bed 5-step stripping PSA cycle with LR and HR from LR purge (96.5% CO₂ purity, 71.1% CO₂ recovery and 57.6 L STP/hr/kg feed throughput). These improved performances were caused mainly by the use of a very small purge to feed ratio (γ=0.02) for the former cycle and a larger one (γ=0.50) for the latter cycle. The former cycle was good for producing CO₂ at high purities and recoveries but at lower feed throughputs, and the latter cycle was useful for obtaining CO₂ at high purities and feed throughputs but at lower recoveries. The best performance of a 4-bed 4-step stripping PSA cycle with HR from CnD was disappointing because of low CO₂ recoveries (99.2% CO₂ purity, 15.2% CO₂ recovery and 72.0 L STP/hr/kg feed throughput). This last result revealed that the recoveries of this cycle would always be much lower than the corresponding cycles with a LR step, no matter the process conditions, and that the LR step was very important to the performance of these HR cycles for this application and process conditions studied.     

Simultaneous determination of uric acid,xanthine, hypoxanthine and caffeine in human blood serum and urine samples using electrochemically reduced graphene oxide modified electrode

This paper describes the fabrication of graphene on glassy carbon electrode (GCE) by electrochemical reduction of graphene oxide (GO) attached through 1,6-hexadiamine on GCE and the simultaneous determination of structurally similar four purine derivatives using the resultant electrochemically reduced GO (ERGO) modified electrode. The electrocatalytic activity of ERGO was investigated toward the oxidation of four important purine derivatives, uric acid (UA), xanthine (XN), hypoxanthine (HXN) and caffeine (CAF) at physiological pH. The modified electrode not only enhanced the oxidation currents of the four purine derivatives but also shifted their oxidation potentials toward less positive potentials in contrast to bare GCE. Further, it successfully separates the voltammetric signals of the four purine derivatives in a mixture and hence used for the simultaneous determination of them. Selective determination of one purine derivative in the presence of low concentrations other three purine derivatives was also realized at the present modified electrode. Using differential pulse voltammetry, detection limits of 8.8 × 10⁻⁸ M, 1.1 × 10⁻⁷ M, 3.2 × 10⁻⁷ M and 4.3 × 10⁻⁷ M were obtained for UA, XN, HXN and CAF, respectively. The practical application of the modified electrode was demonstrated by simultaneously determining the concentrations of UA, XN, HXN and CAF in human blood plasma and urine samples.     

Carbon black and propylene oxidation over Ru/CoxMgyAl2Oz catalysts

The effects of Co_xMg_yAl₂O_z mixed oxides composition and ruthenium addition on the oxidation of propylene and carbon black (CB) were investigated. Different reactive cobalt and ruthenium oxide species were formed following calcination at 600 °C. The addition of ruthenium was beneficial for the CB oxidation under “loose contact” conditions and for propylene oxidation when the cobalt content was intermediate to low. The calculated activation energy for CB oxidation was decreased from 151 kJ mol⁻¹ for the uncatalyzed reaction to 111 kJ mol⁻¹ over the best catalyst.     

Preparation and Evaluation of Some Terpolymers as Lube Oil Additives

In the present work, some polymeric additives were prepared to use as viscosity index improvers and pour point depressants for lube oil via copolymerization of hexadecylacrylate and dodecylacrylate with styrene. Structure of the prepared compounds was confirmed by infrared spectroscopy and nuclear magnetic resonance. The molecular weights of the prepared copolymers were determined by using gel permeation chromatograph. The efficiency of the prepared terpolymers as viscosity index improvers and pour point depressants for lube oil was investigation. It was found that all the prepared terpolymers are effective as viscosity index improvers and pour point depressants. The viscosity index of the prepared terpolymers increases with increasing the concentration of the additives and increases by increasing the percentage of hexadecylacrylate until 70%. The best result for viscosity index of the prepared terpolymers is when the percentage of styrene is 10%. The pour point of the prepared compound decreases with decreasing concentration of additive used.