低温加氢催化剂的设计: 理论与实践

简要总结了我们在C=C及C=O双键低温加氢双金属催化剂方面的最新研究成果. 首先, 我们以环己烯加氢为探针反应, 证明了平行使用多种研究手段的重要性, 包括单晶表面的基础研究与DFT计算, 多晶表面的合成与表征, 负载型催化剂的制备与性能测试等. 其次, 总结了双金属催化剂在其他加氢反应, 如丙烯醛C=O双键的选择性加氢, 苯的低温加氢, 以及乙炔的选择性加氢等反应中的应用. 最后, 讨论了利用金属碳化物代替贵金属Pt以减少双金属催化剂中Pt用量的可能性.     

Properties and analytical applications of the heteropolymolybdates of phosphorus, arsenic, silicon and germanium-IV Determination of phosphomolybdic and silicomolybdic acids via the molybdenum content, with phenylfluorone

Procedures are proposed for the determination of phosphorus and silicon in the ppM range, by extraction of phosphomolybdic and silicomolybdic acids with organic solvent, decomposition of the complex and spectrophotometric determination of its molybdenum content.     

Determination of association constants between enantiomers of orciprenaline and methyl-beta-cyclodextrin as chiral selector by capillary zone electrophoresis using a partial filling technique

The principles for the determination of conditional association constants of enantiomers by capillary zone electrophoresis employing a partial filling technique (PFT) using methyl-beta-cyclodextrin as chiral selector is presented. Orciprenaline was used as a model compound. Partial filling is a separation technique, where different lengths of the chiral selector solution are introduced into the capillary to a final zone length shorter than the effective length of the capillary, prior to application of the solutes. Lengthening of the separation zone results in improving enantioresolution in addition to decreasing electrophoretic mobility of the enantiomers, because of longer interaction time between the solute and chiral selector. The degree of the reduction in electromobility depends on the affinity of the solute to the chiral selector, i.e. strength of the complex formed between the solute and cyclodextrin. The decrease in the electrophoretic mobility with increasing length of the separation zone is used for determination of the association constant. The association constants of the enantiomers of orciprenaline and the chiral selector were evaluated from the slope of the plot, observed electrophoretic mobility versus the ratio between the length of the separation zone and the effective length of the capillary. It was found that the association constants were independent of the chiral selector concentration. The mean values were 110 M(-1) and 160 M(-1) for respective enantiomer. Constants obtained by a conventional CE technique were in good agreement with those from the PFT experiments. The highest enantioselectivityy was obtained when about 50% of the solute was distributed to the selector phase.     

Possible Role of the Iron Coordination Sphere in Hemoprotein Electron Transfer Self-Exchange: (1)H NMR Study of the Cytochrome c-PMe(3) Complex

The rates of self-exchange electron transfer in the trimethylphosphine complex of cytochrome c have been measured by an NMR technique over a large range of ionic strengths. The rate constant is 1.56 x 10(4) M(-)(1) s(-)(1) at 23 degrees C (&mgr; = 0.34 M) at pH 6.9. Dependence on ionic strength of the rate constant is treated by van Leeuwen theory. Extrapolation of the rate constant to infinite ionic strength gives a rate constant of 3.9 x 10(5) M(-)(1) s(-)(1). This rate constant is compared with others reported for myoglobin and cytochrome b(5)(). The values for these systems range over 2 orders of magnitude with myoglobin-PMe(3) < cytochrome b(5)() < cytochrome c-PMe(3) < cytochrome c. Analysis of the data in terms of Marcus theory gives a reorganization energy, lambda, for self-exchange of 0.75 eV mol(-)(1) for cytochrome c-PMe(3). Substitution of Met-80 by PMe(3) appears to influence only weakly the rearrangement barrier to electron transfer.     

超声波对亲核加成反应的影响：氰乙基醚香料的合成

超声波在实践中已被多方面采用,近年在化学领域中用于有机合成,已成为热门课题。由于在超声波作用下,体系中产生空穴作用,局部产生高温高压,所释放出的能量,足以使有机分子发生反应,从而促进了反应进行。如用于取     

Analysis of free fatty acids and fatty acid phenacyl esters in vegetable oils and margarine by capillary electrochromatography

Capillary electrochromatography (CEC) has been utilized to analyze free fatty acids (FFAs) and fatty acid phenacyl esters (FAPEs) originating from vegetable oils and margarine. The analyses were performed on capillaries 25 and 40 cm long, 100 microm ID, and packed with 3 microm Hypersil ODS. Isocratic elution was achieved with the mobile phase acetonitrile/50 mM 2-(N-morpholino)ethane sulfonic acid (MES), pH 6, at a ratio of 9:1. For quantitative analysis, the formation of FAPE derivatives is preferred. Moreover, the number of double bonds in the FAPEs can be elucidated by measuring the UV absorbance ratio of 240:210 nm. For the determination of the oleate/elaidate ratio in margarines, the FFAs are analyzed because of overlap of elaidate/palmitate in FAPE analysis. Data obtained with CEC and micro liquid chromatography (LC) were compared and CEC was found to be far superior in terms of efficiency and speed of analysis. Important selectivity differences were noted between micro LC on highly endcapped ODS and CEC on the silanol-rich Hypersil ODS.     

Measuring the work of adhesion between a soft confined film and a flexible plate

We present a theoretical and experimental study of a method for the determination of the adhesion strength between a thin elastomeric film bonded to a rigid substrate and a flexible plate in a geometry common in the peel test. In particular, we characterize the work of adhesion in terms of the length of an equilibrium crack, generated by a spacer of known thickness wedged between the flexible plate and adhesive film, and the elastic and geometric properties of the film and the plate. We treat both the limit of perfect bonding and that of perfect slippage at the interface of the adhesive film and the flexible plate. A series of experiments allow us to verify the theory quantitatively and thus validate our method, which ought to be of value in many technological situations.     

Efficient flow injection and sequential injection methods for spectrophotometric determination of oxybenzone in sunscreens based on reaction with Ni(II)

Spectrophotometric determination of a widely used UV-filter, such as oxybenzone, is proposed. The method is based on the complexation reaction between oxybenzone and Ni(II) in ammoniacal medium. The stoichiometry of the reaction, established by the Job method, was 1:1. Reaction conditions were studied and the experimental parameters were optimized, for both flow injection (FI) and sequential injection (SI) determinations, with comparative purposes. Sunscreen formulations containing oxybenzone were analyzed by the proposed methods and results compared with those obtained by HPLC. Data show that both FI and SI procedures provide accurate and precise results. The ruggedness, sensitivity and LOD are adequate to the analysis requirements. The sample frequency obtained by FI is three-fold higher than that of SI analysis. SI is less reagent-consuming than FI.     

A fibrous hypercrosslinked sorbent prepared on PP-ST-DVB matrix via post-crosslinking reaction

A fibrous sorbent possessing abundant micropore structure was firstly prepared via post-crosslinking reaction on the PP-ST-DVB original fiber. Its micromorphology and sorptive properties were investigated, and the results demonstrated that the novel fibrous hypererosslinked sorbent has narrow pore-size distribution, small average porous radius （1.90 nm）, high specific surface area （362.31 m^2/g）, and fine sorptive properties for small organic molecules.     

Novel acyl alpha-pyronoids, dictyopyrone A, B, and C, from Dictyostelium cellular slime molds

For the elucidation of the diversity of secondary metabolites of Dictyostelium cellular slime molds, we investigate the constituent of three species of slime molds. From the methanol extract of their fruit bodies, we obtained three novel compounds, dictyopyrone A (1) and B (2) from D. discoideum and D. rhizoposium and dictyopyrone C (3) from D. longosporum. They possess a unique alpha-pyrone moiety with a side chain at the C-3 position. Their relative structures were elucidated by spectral means, and the absolute configuration was confirmed by asymmetric synthesis of 1. Since these compounds were obtained from different species of Dictyostelium slime molds, they may be a type of compound common to this genus.