New diphosphite ligands for enantioselective asymmetric hydroformylation

A series of new diphosphite ligands have been easily prepared from BINOL derivatives; moderate enantioselectivities (up to 80% ee) and excellent regioselectivities (b/l up to 98/2) have been achieved in the Rh-catalyzed asymmetric hydroformylation of vinyl acetate.     

Prediction of paper permanence by accelerated aging II. Comparison of the predictions with natural aging results

Accelerated aging tests are credible and useful to predict paper permanence only if such tests can be shown to correlate with natural aging. In the first part of this study, a kinetic model was developed based on the accelerated aging results. In this report, we have shown that this kinetic model can indeed predict the natural aging results of lignin-free sheets with a statistical confidence. This is the first quantitative comparison of accelerated aging with natural aging.     

On-column amperometric detection in capillary electrophoresis with an improved high-voltage electric field decoupler

The analysis of polyamide-6 oligomers and polymer is usually performed with expensive fluorinated alcohols like 2,2,2-trifluoroethanol (TFE) or 1,1,1,3,3,3-hexafluoroisopropanol (HFIP). Formic acid is well known as a mobile phase additive to adjust pH in reversed-phase high-performance liquid chromatography. However, formic acid is seldom used as a modifier to perform gradient elution chromatography on octadecyl-modified silica-based columns. Here we demonstrate the determination of cyclic and linear polyamide-6 oligomers using formic acid as a modifier on an octadecyl-modified silica-based column. This column was shown to be stable for more than 5000 column volumes, even when a mobile phase of 65-95% formic acid in water at a flow of 1 ml/min is applied. With formic acid under the conditions used (65-95% formic acid in water) the oligomers are retained on the column, while the polymer does not precipitate. In comparison, during adsorption and separation with a HFIP gradient, precipitation of the polymer occurs. The implications of the different separation mechanisms, i.e., adsorption vs. precipitation chromatography are discussed. Loadability is shown to be much better with the formic acid system. However, with formic acid as a modifier UV detection below 250 nm is not feasible. The less sensitive evaporative light scattering detector is used to detect the polyamide oligomers in the formic acid phase. In addition it is shown that capillary zone electrophoresis (CZE) with UV-absorbance detection using HFIP is an attractive combination as HFIP is UV-transparent and CZE allows low modifier consumption.     

Screening and analysis of bioactive compounds with biofingerprinting chromatogram analysis of traditional Chinese medicines targeting DNA by microdialysis/HPLC

Biofingerprinting chromatogram analysis, which is defined as the comparison of fingerprinting chromatograms of the extract of traditional Chinese medicines (TCMs) before and after the interaction with biological systems (DNA, protein, cell, etc.), was proposed for screening and analysis of the multiple bioactive compounds in TCMs. A method of microdialysis sampling combined with high performance liquid chromatography (HPLC) was applied to the study of DNA-binding property for the extracts of TCMs. Seven compounds were found to bind to calf thymus DNA (ct-DNA) from the TCMs of Coptis chinensis Franch (Coptis), but only three ones from Phellodendron amurense Rupr. (Phellodendron) and none from Sophoraflavescens Ait. (Sophora) to bind to ct-DNA, respectively. Three of them were identified as berberine, palmatine and jatrorrhizine and their association constants (K) to ct-DNA were determined by microdialysis/HPLC. Competitive binding behaviors of them to ct-DNA were also investigated.     

杨村烟煤与石油渣油共处理反应特性的研究

用共振搅拌反应器研究了山东兖州杨村的烟煤与北京燕山石化公司的石油渣油共处理液化的反应过程，考察了反应温度和反应时间对煤液化转化率及产物中前涸青烯，苯可溶组分的影响。     

酞菁化合物LB单分子膜的SERRS

酞菁类化合物具有优良的光电特性,选择适当的取代侧链可得到稳定的LB成膜材料,可望在微电子器件等方面获得重要的应用.本工作观测了四-4-(2,4-二特戊基苯氧基)酞菁铜(CuPc(Dt-PP)_4)在银岛膜上的LB单分子层的表面增强共振拉曼散射(SERRS)光谱。比较其固体粉末的共振拉曼散射(RRS)光谱,讨论了酞菁铜分子大环在载片表面的取向及其可能的原因。1 实验CuPc(Dt-PP)_4样品由陈文启等合成,经元素分析、IR、NMR、色谱等研究确认其结构如图1所示.银岛膜用真空蒸镀法制备在玻璃载片上。用同时蒸镀在铜网上的银膜的透射电     

Solution structure and thermolysis of Cobeta-5'-deoxyadenosylimidazolylcobamide, a coenzyme B12 analogue with an imidazole axial nucleoside

The solution structure of Cobeta-5'-deoxyadenosylimidazolylcobamide, Ado(Im)Cbl, the coenzyme B(12) analogue in which the axial 5,6-dimethylbenzimidazole (Bzm) ligand is replaced by imidazole, has been determined by NMR-restrained molecular modeling. A two-state model, in which a conformation with the adenosyl moiety over the southern quadrant of the corrin and a conformation with the adenosyl ligand over the eastern quadrant of the corrin are both populated at room temperature, was required by the nOe data. A rotation profile and molecular dynamics simulations suggest that the eastern conformation is the more stable, in contrast to AdoCbl itself in which the southern conformation is preferred. Consensus structures of the two conformers show that the axial Co-N bond is slightly shorter and the corrin ring is less folded in Ado(Im)Cbl than in AdoCbl. A study of the thermolysis of Ado(Im)Cbl in aqueous solution (50-125 degrees C) revealed competing homolytic and heterolytic pathways as for AdoCbl but with heterolysis being 9-fold faster and homolysis being 3-fold slower at 100 degrees C than for AdoCbl. Determination of the pK(a)'s for the Ado(Im)Cbl base-on/base-off reaction and for the detached imidazole ribonucleoside as a function of temperature permitted correction of the homolysis and heterolysis rate constants for the temperature-dependent presence of the base-off species of Ado(Im)Cbl. Activation analysis of the resulting rate constants for the base-on species show that the entropy of activation for Ado(Im)Cbl homolysis (13.7 +/- 0.9 cal mol(-1) K(-1)) is identical with that of AdoCbl (13.5 +/- 0.7 cal mol(-1) K(-1)) but that the enthalpy of activation (34.8 kcal mol(-1)) is 1.0 +/- 0.4 kcal mol(-1) larger. The opposite effect is seen for heterolysis, where the enthalpies of activation are identical but the entropy of activation is 5 +/- 1 cal mol(-1) K(-1) less negative for Ado(Im)Cbl. Extrapolation to 37 degrees C provides a rate constant for Ado(Im)Cbl homolysis of 2.1 x 10(-9) s(-1), 4.3-fold smaller than for AdoCbl. Combined with earlier results for the enzyme-induced homolysis of Ado(Im)Cbl by the ribonucleoside triphosphate reductase from Lactobacillus leichmannii, the catalytic efficiency of the enzyme for homolysis of Ado(Im)Cbl at 37 degrees C can be calculated to be 4.0 x 10(8), 3.8-fold, or 0.8 kcal mol(-1), smaller than for AdoCbl. Thus, the bulky Bzm ligand makes at best a <1 kcal mol(-1) contribution to the enzymatic activation of coenzyme B(12).     

Large third-order nonlinear optical properties of C70 fullerene in the infrared regime

The nonlinear third-order optical susceptibility of C₇₀ in a toluene solution is measured for the first time by the method of degenerate four-wave mixing using 10 ns laser pulses at 1.06 m. The third-order susceptibility X _in ⁽³⁾ is 5.6×10^–12 esu for a C₇₀ toluene solution at a concentration of 0.476 g/l. The correspondent magnitude of the hyperpolarizability ₁₁₁₁ of the C₇₀ molecule is 1.2×10^–30 esu which is in a good agreement with the prediction given by the model of a free electron in a spherical box.     

硬脂酸晶体压力效应的FT-IR光谱研究

 本文在0~4 GPa范围内研究了预压力对硬脂酸晶体的相关场劈裂和固态-熔融态相变过程的影响。通过γCH₂面内摇摆振动模和γ'CH₂相关场模的强度和频率变化,发现预压力对晶体内的相关场合分子链取向有明显的影响。预压力对硬脂酸的熔点虽然没有影响,但对γ'CH₂模有“硬化”作用。并且由此出发,对硬脂酸的预熔过程作了讨论。