含氟膦叶立德的^1^3C和^3^1P核磁共振研究

本文报道了三十一个含氟磷叶立德的^1^3C和^3^1P核磁共振研究结果, 含氟磷叶立德的通式为: (C6H5)3P=C(X)(CO)Rf, 其测定的核磁共振数据列于下表.     

2D NMR对Sarcophine所有^1H NMR和^1^3C NMR归属的指定

从中国南海软珊瑚Sarcophyton molle中分离得到大环二萜内酯Sarcophine(1)。本文利用^1H-^1H COSY，HMQC，HMBC等二维谱手段首次对Sarcophine所有^1H NMR、^1^3C NMR的信号归属进行了完全的指定。并第一次报道了其^1^3C NMR数据。     

乙酰苯胺衍生物的^1H和^1^3C NMR 谱的研究

本文测定了10个乙酰苯胺衍生物的^1H, ^1^3C NMR谱, 采用质子自旋去偶, 质子选择去偶, 质子偏共振去偶, 质子去偶的^1^3C DEPT和选择INEPT等技术对其谱线进行归属。系统地研究了围绕羰基碳氮键的受阻旋转, 确认了该类化合物在溶液中存在E和Z型构象体, 并探讨了各种取代基对形成异构体比例的影响。     

NMR位移试剂Eu(fod)~4^-对锍盐^1H和^1^3C NMR的影响

合成了八种新的四氟硼酸二甲基苯基锍，用元素分析和核磁共振对其结构进行了表征。研究了以CDCl~3为溶剂，NMR位移试剂Eu(fod)~4^-对所合成锍盐的^1H和^1^3C NMR的影响。结果表明，Eu(fod)~4^-是一个对锍盐非常有效的位移试剂，且Eu(fod)~4^-对二甲基苯基锍盐之甲基的^1H和^1^3C NMR的位移呈线性关系。     

有机磷化合物的NMR研究 III: 不对称取代1,3,2-二氮磷杂环戊烷的^1^3C NMR

本文报道了十个不对称取代1,3,2-二氮磷杂环戊烷的^1^3C核磁共振谱, 利用^1^3C自旋-晶格弛豫时间确定了用其它去偶技术难以确定的信号的归属, 讨论了偶合常数与构象的关系.     

^1^3C化学位移在达玛烷型皂甙结构研究中的应用

本文将迄今为止国内外文献报道的200余种达玛烷型皂甙类化合物的^1^3C化学位移按其结构特征分类整理，以原人参二(三)醇等为模型化合物，讨论了皂甙元结构变化引起的位移变化(△δC)规律。     

青蒿素及其一类物的结构和合成:XXIV,青蒿素转化为天然的△^1^1^(^1^3^)-脱氢青蒿素

本文研究了青蒿素及其一类物的结构和合成。青蒿素具有很高的稳定性, 本文即设想通过苯硒化合物的氧化消除反应, 将其转变为天然的△^1^1^(^1^3^)一脱氢青蒿素。     

青蒿素及其一类物的结构和合成:XXIV,青蒿素转化为天然的△^1^1^(^1^3^)-脱氢青蒿素

本文研究了青蒿素及其一类物的结构和合成。青蒿素具有很高的稳定性, 本文即设想通过苯硒化合物的氧化消除反应, 将其转变为天然的△^1^1^(^1^3^)一脱氢青蒿素。     

α-和β-K6H[GeW9V3O40].xH2O的合成及其^5^1V和^1^8^3W核磁共振研究

本文报道了α-和β-K6H[GeW9V3O40].xH2O的合成及其^5^1V和^1^8^3W NMR研究。^5^1V NMR谱只有一个单峰, ^1^8^3W NMR谱中有两个峰, 相对强度为2:1, 其^2J~w~-~o~-~-~w偶合常数分别为19.35和16.73Hz, 表明其阴离子分别为A型α-和β-Keggin结构, 即三个VO6八面体是角顶共用。     

1, 3-双磷(膦)酰基丙烯类化合物的^1H、^3^1P NMR研究

本文报道了标题类化合物中十个化合物的^1H和^3^1PNMR的研究结果。其中分别运用了2DJ分解谱以及异核COSY谱等多种技术,解析了它们的^1H和^3^1P图谱,从而证实了合成反应的区域选择性和立体选择性。文章中,讨论了手性中心或其它因素而表现出的不等性;讨论了影响δ~P和J~p~H数值的各种因素:还报道了比较少见的^3^1P-^3^1P之间的远程偶合。其中,顺式产物的^4J~P~P数值(约9Hz)大于反式产物的^4J~P~P(约7Hz)。     

Acid hydrolysis of carboxymethylcellulose of low degree of substitution

Cotton cellulose was swollen in a sodium hydroxide solution and carboxymethylated by a two-bath method for different periods of time for each process. The kinetics of acid hydrolysis and the crystallinity of the swollen and carboxymethylated samples were measured. The proportion of broken bonds, rate constants for hydrolysis, and permeability of cellulose to hydrolyzing agents were calculated. The susceptibility of glycosidic linkages to acid hydrolysis was improved by carboxymethylation more than by swelling in alkali. The increased accessibility of carboxymethylcellulose to acid was regarded as a consequence of increased intra-and intercrystalline swelling and of the glycosidic bonds' weakness caused by the electron-attracting carboxymethyl group on the C-6 position.     

Effects of reprocessing of oxobiodegradable and non-degradable polyethylene on the durability of recycled materials

The use of plastics is steadily increasing in our daily lives, and plastics are the fastest-growing component of the waste stream. Although the efficiency of plastic recycling is increasing, plastics are often seen as a permanent environmental problem because of littering. The introduction of oxobiodegradable polyolefins (OBDs), containing prodegradant additives, is considered to be a way to reduce this problem by enabling the fast degradation of plastics in the environment. The prodegradant additives form radicals that attack the polymer chains, causing chain scissions and generation of low molecular mass oxidation products that can be consumed by microorganisms. There is, however, a concern that the prodegradant additives will present a problem if OBD materials end up in the conventional plastic recycling streams. The present study therefore highlights the impact of mixing OBD materials with conventional polyolefins to evaluate the impact on the remaining service life of the recyclates.The study included the use of two different OBDs, mixed in different proportions (10% and 20%) in a conventional polyethylene. The remaining service life of the mixtures was evaluated by monitoring the reduction in tensile strain after exposure to thermo-oxidative degradation at 70 °C, compared with a pure polyethylene. The impact of stabilizer content in the mixtures was also evaluated together with the effect of mixing partially degraded OBDs into the recyclate.The results show that the incorporation of minor fractions of OBD materials in the existing recycling streams will not create a severe effect on the service life of the recyclates as long as the polymer mixture possesses a reasonable degree of stabilization.     

纳米碳管的电化学贮锂性能

用透射电镜、高分辩透射电镜、X射线衍射和拉曼光谱表征了用催化热解法制备的纳米碳管的结构,研究了纳米碳管的电化学嵌脱锂性能.以纳米级铁粉为催化剂热解乙炔气得到的纳米碳管石墨化程度较低,结构中存在褶皱的石墨层、乱层石墨和微孔等缺陷,具有较高的贮锂容量,初始容量为640mAh/g,但循环稳定性较差.而以纳米级氧化铁粉为催化剂热解乙烯得到的纳米碳管结构比较规则,循环稳定性较好,但贮锂容量较低,初始容量为282 mAh/g.讨论了纳米碳管的结构对其温度特性和不同电流密度下的充放电容量的影响.     

Heats of Mixing of Mixed Solvent Solutions of Alkali Metal Salts of Substituted Benzenesulfonic Acids

The enthalpy change on mixing solutions of methyl-substituted benzenesulfonic acids and their salts, with salts having a common cation or anion, at constant ionic strength in mixtures of 1,4-dioxane with water, were measured at 25°C. The heat effects of mixing solutions having a common anion increase almost linearly with the reciprocal value of the dielectric constant of the solvent. The heat effects of mixing solutions having a common cation, which are all negative in water-rich solutions, become endothermic after a certain value of the dielectric constant is passed. The results are discussed in terms of the solute-solvent structural properties. This revised version was published online in July 2006 with corrections to the Cover Date.     

New Algorithm of Spectral Analysis of Elements in Presence of Matrix Interferences

Abstract

This work suggests a new algorithm for the elemental analysis, which permits taking into account both the multiplicative and additive matrix effects, a matrix composition being unknown. The use of this algorithm in the development of analysis techniques at any set of objects may appear to be successful at arbitrarily selected measurement conditions. The basis of the algorithm consists of a combination of pattern recognition and standard addition technique (PRSA). The main concept of PRSA is to predict a function approximating satisfactorily a calibration dependence for a specific object and then to determine an unknown concentration using a nonlinear addition technique, all the aforementioned being based on easily obtained information on an analyzed object and measurement conditions. The abilities of the proposed algorithm were demonstrated by the example of strontium determination by the flame atomic absorption spectrometry in superconducting systems.     

Performance comparison of three types of high-speed counter-current chromatographs for the separation of components of hydrophilic and hydrophobic color additives

The performance of three types of high-speed counter-current chromatography (HSCCC) instruments was assessed for their use in separating components in hydrophilic and hydrophobic dye mixtures. The HSCCC instruments compared were: (i) a J-type coil planet centrifuge (CPC) system with a conventional multilayer-coil column, (ii) a J-type CPC system with a spiral-tube assembly-coil column, and (iii) a cross-axis CPC system with a multilayer-coil column. The hydrophilic dye mixture consisted of a sample of FD&C Blue No. 2 that contained mainly two isomeric components, 5,5'- and 5,7'-disulfonated indigo, in the ratio of ～7:1. The hydrophobic dye mixture consisted of a sample of D&C Red No. 17 (mainly Sudan III) and Sudan II in the ratio of ～4:1. The two-phase solvent systems used for these separations were 1-butanol/1.3M HCl and hexane/acetonitrile. Each of the three instruments was used in two experiments for the hydrophilic dye mixture and two for the hydrophobic dye mixture, for a total of 12 experiments. In one set of experiments, the lower phase was used as the mobile phase, and in the second set of experiments, the upper phase was used as the mobile phase. The results suggest that: (a) use of a J-type instrument with either a multilayer-coil column or a spiral-tube assembly column, applying the lower phase as the mobile phase, is preferable for separating the hydrophilic components of FD&C Blue No. 2; and (b) use of a J-type instrument with multilayer-coil column, while applying either the upper phase or the lower phase as the mobile phase, is preferable for separating the hydrophobic dye mixture of D&C Red No. 17 and Sudan II.     

An expedient synthesis of the repeating unit of the acidic polysaccharide of the bacteriolytic complex of lysoamidase

The first synthesis of the trisaccharide repeating unit of the acidic polysaccharide of the bacteriolytic complex of lysoamidase is presented. The construction is based on a linear glycosylation strategy that starts from the reducing end and employs thio- and selenoglycosides in a highly stereoselective manner by a single set of activation conditions. The thus-formed trisaccharide is selectively deprotected and oxidised, after which a final deprotection step furnishes the desired repeating unit.     

Determination of Kinetic Equations of Alkaline Activation of Blast Furnace Slag by Means of Calorimetric Data

The alkaline activation of blast furnace slag promotes the formation of new cement materials. These materials have many advantages over ordinary Portland cement, including high strength, low production cost and good durability. However, many aspects of the chemistry of alkaline activated slags are not yet very well understood. Some authors consider that these processes occur through a heterogeneous reaction, and that they can be governed by three mechanisms: a) nucleation and growth of the hydrated phase; b) phase boundary interactions and c) any diffusion process though the layer of hydration products. The aim of this paper was to determine the mechanism explaining the early reaction of alkaline activation of a blast furnace slag through the use of calorimetric data. A granulated blast furnace slag from Avilés (Spain) with a specific surface of 4450 cm²> g^-1 was used. The alkaline activators used were NaOH, Na₂CO₃ and a mix of waterglass (Na₂SiO₃·nH₂O and NaOH. The solution concentrations were constant (4% Na₂O with respect to the slag mass). The solutions were basic (pH 11-13). The mixes had a constant solution/slag ratio of 0.4. The thermal evolution of the mixes was monitored by conduction calorimetry. The test time was variable, until a rate of heat evolution equal to or less than 0.3 kJ kg^-1 h^-1 was attained. The working temperature was 25°C. The degree of hydration (α) was determined by means of the heat of hydration after the induction period. The law governing the course of the reaction changes at a certain degree of hydration. From a generally accepted equation, the values of α at which the changes are produced were determined. These values of α depend on the nature of the alkaline activator. Nevertheless, for high values of α, the alkaline activation of slag occurs by a diffusion process. This revised version was published online in July 2006 with corrections to the Cover Date.     

Micromechanical modeling of the tensile behavior of oriented polyethylene

The stacked lamellar morphology commonly found in extruded semicrystalline materials has a strong influence on the flow direction, with respect to the loading direction, and on the stability and localization phenomena in tensile experiments. A multiscale numerical model was used to simulate the effect on the macroscopic behavior of a stacked lamellar microstructure. The model established a link between the microscopic, the mesoscopic, and the macroscopic levels. The constitutive properties of the material were identified for the crystallographic and amorphous domains. The average fields of an aggregate of individual phases, having preferential orientations, formed the constitutive behavior of the extruded material. The microscopic morphology of the extruded high‐density polyethylene is based on wide‐angle X‐ray diffraction experiments. The macrostructure was described by a finite element model. The microstructure‐induced deformation hardening in the extrusion direction was found to stabilize the macrostructure when it was loaded in the flow direction. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2983–2994, 2004