Derivatization in Liquid Chromatography/Mass Spectrometric Analysis of Neurosteroids

1　Ｉｎｔｒｏｄｕｃｔｉｏｎ　Ｇａｓｃｈｒｏｍａｔｏｇｒａｐｈｙ/ｍａｓｓｓｐｅｃｔｒｏｍｅｔｒｙ (ＧＣ/ＭＳ)ａｎｄｌｉｑｕｉｄｃｈｒｏｍａｔｏｇｒａｐｈｙ/ｍａｓｓｓｐｅｃｔｒｏｍｅｔｒｙ (ＬＣ/ＭＳ) ,ｒｅｐｒｅｓｅｎｔａｔｉｖｅｓｏｆｔｈｅｈｙｐｈｅｎａｔｅｄｔｅｃｈｎｉｑｕｅｓ ,ａｒｅｓｏｍｅｏｆｔｈｅｍｏｓｔｒｅｌｉａｂｌｅａｎａｌｙｔｉｃａｌｍｅｔｈｏｄｓ ,ｗｈｉｃｈａｒｅｔｈｅｓｙｎｅｒｇｉｓｔｉｃｃｏｍｂｉｎａｔｉｏｎｏｆｔｗｏｐｏｗｅｒｆｕｌａｎａｌｙｔｉｃａｌｔｅｃｈｎｉｑｕｅｓ;…     

醋酸乙烯酯在硅橡胶上的辐射接枝研究

研究了不同溶剂中的醋酸乙烯酯在硅橡胶上的辐射接技状况及接枝后硅橡胶表面结构情况．结果表明：（１）在硅橡胶－乙酸乙酯－醋酸乙烯酯体系中，接枝有自加速效应；（２）适量加入对苯二酚，接枝诱导期延长，接枝速率下降，凝胶效应消失，辐射接技经验关联式为ＲＰ＝０．２７×［Ｄ］（－０．５６０）×［Ｉ］（０．４９０）×［Ｃ］（０．９２０），接核反应为扩散控制反应；（３）不同的溶剂对硅橡胶接枝有不同的影响，如甲醇发生敏化作用，提高接枝速率，而苯发生惰化作用，降低接枝速率；（４）在合适的甲醇和苯配比时，接枝反应几乎恒速进行，用扫描电镜（ＳＥＭ）观察断面，接枝区比较均一，出现微相分离．     

Influence of the heating rate on the temperature profiles and on the conversion rate of powdery cellulose and pine sawdust

An experimental study of the thermal decomposition of powdered cellulose and pine sawdust has been performed. The influence of the heating rate on the temperature profiles in the sample and on the solid conversion rate has been studied. A mathematical model without adjustable parameters has been used to calculate the temperature at different points in the solid bed and the average total solid conversion. The experimental results have been compared with those calculated by the model. A good agreement has been obtained for sawdust. Some differences are observed for cellulose at high heating rates, and the influence of the thermal conductivity and the reaction heat on the results has been analysed.     

Spectrothermal investigation of the decomposition course of lanthanum acetate hydrate

Thermogravimetry, differential thermal, X-ray diffraction and infrared spectroscopy analyses showed La(CH₃COO)₃·1.5H₂O to decompose completely at 700°C yielding La₂O₃. The results revealed that the compound dehydrates in two steps at 130 and 180°C, and recrystallizes at 210°C. Water thus produced hydrolyzes surface acetates (at 310°C), releasing acetic acid into the gas phase. At 334°C, the anhydrous acetate releases gas phase CH₃COCH₃ to give La₂(CO₃)₃ residue, which decomposes to La₂O₂(CO₃) via the intermediate La₂O(CO₃)₂. On further heating up to 700°C, La₂O₃ is formed. IR spectroscopy of the gaseous products indicated a chemical reactivity at gas/solid interfaces formed throughout the decomposition course. As a result, CH₃COCH₃ was involved in a surface-mediated, bimolecular reaction, releasing CH₄ and C₄H₈ (isobutene) into the gas phase. Non-isothermal kinetic parameters, the rate constantk, frequency factorA, and activation energy ΔE, were calculated on the basis of temperature shifts experienced in the thermal processes encountered, at various heating rates (2–20 deg·min^?1).     

Toward the total synthesis of elisapterosin B: A Hg(OTf)(2)-promoted diastereoselective intramolecular Friedel-Crafts alkylation reaction

As part of an approach to the synthesis of the antitubercular agent elisapterosin B, we prepared two different chiral, non-racemic olefinic substrates and examined their diastereoselective ring closure using mercury salts. The effort yielded potential precursors to elisapterosin B in good yield with good to excellent diastereocontrol.     

Study on the toughening mechanism of PP/EVA dynamically crosslinked blend

The toughening mechanism of polypropylene (PP)/ethylene-co-vinyl acetate (EVA) dynamically crosslinked blend was investigated. The results indicated that dynamical crosslinking technology not only improved the interfacial adhesion between PP and EVA, but also increased the mechanical properties of PP/EVA blend. The quantitative and qualitative analysis of scanning electron microscopy (SEM) micrographs demonstrated that dynamical crosslinking technology could refine EVA particles in PP/EVA blend and promote the size distribution of EVA particles. The critical matrix ligament thickness of dynamically crosslinked and uncrosslinked blend was about 0.55 μm and 0.6 μm, respectively, indicating that the brittle-ductile transition occurred. Dynamic mechanical analysis (DMA) results illustrated that the tan δ peak of PP component in the dynamically crosslinked blend moved toward lower temperature compared with that of pure PP and the PP component in uncrosslinked blend; and the tan δ value of the dynamically crosslinked blend was higher than that of the uncrosslinked blend, which interpreted the toughening mechanism of dynamical crosslinking technology from the dynamic mechanical property of the blend.     

Poly(N,N′-dibromo-N-ethyl-benzene-1,3-disulfonamide), N,N,N′,N′-tetrabromobenzene-1,3-disulfonamide and novel poly(N,N′-dibromo-N-phenylbenzene-1,3-disulfonamide) as powerful reagents for benzylic bromination

N,N,N′,N′-Tetrabromobenzene-1,3-disulfonamide [TBBDA], poly(N,N′-dibromo-N-ethyl-benzene-1,3-disulfonamide) [PBBS], and novel poly(N,N′-dibromo-N-phenylbenzene-1,3-disulfonamide) [PBPS] can be used for bromination of benzylic positions in solvent.     

Oxidative interactions of propene with acetic acid on a Pd-zeolite catalyst

The interactions between C₃H₆, AcOH and O₂ were investigated on 1.5 % Pd/TsVM catalysts prepared with and without addition of 15 % AcOK. Three states for surface oxygen on the promoted catalyst were distinguished. Two of them are involved in the oxidation of AcOH and C₃H₆ to CO₂ and H₂O, whereas the adsorbed species of the third type participates in the formation of allyl acetate. The O/Pd ratios for the promoted catalyst fall in the range from 3 to 4, the nonpromoted system is characterized by an O/Pd value of 0.5. IR-spectral data are used to discuss the reaction scheme for the formation of allyl acetate. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1721–1726, October, 1993.     

Biological production of ethanol from coal synthesis gas

The anaerobic bacteriaClostridium ljungdahlii produces ethanol and acetate from CO, CO₂, and H₂ in synthesis gas. Early studies with the bacterium showed that relatively high concentrations of ethanol could be produced by lowering the fermentation pH and eliminating yeast extract from the medium in favor of a defined medium. This article presents the results from a medium development study based on the aerobic bacteriumEscherichia coli. The results of continuous-reactor studies in a continuously stirred tank reactor (CSTR) with and without cell recycle are shown to demonstrate the utility of this improved medium.     

Natural Cellulose Substance Based Energy Materials

Natural cellulose substances have been proven to be ideal structural templates and scaffolds for the fabrication of artificial functional materials with designed structures, psychochemical properties and functionalities. They possess unique hierarchically porous network structures with flexible, biocompatible, and environmental characteristics, exhibiting great potentials in the preparation of energy-related materials. This minireview summarizes natural cellulose-based materials that are used in batteries, supercapacitors, photocatalytic hydrogen generation, photoelectrochemical cells, and solar cells. When natural cellulose substances are employed as the structural template or carbon sources of energy materials, the three-dimensional porous interwoven structures are perfectly replicated, leading to the enhanced performances of the resultant materials. Benefiting from the mechanical strengths of natural cellulose substances, wearable, portable, free-standing, and flexible materials for energy storage and conversion are easily obtained by using natural cellulose substances as the substrates.