物理有机化学前沿领域两个主要方面--有机分子簇集和自由基化学研究

物理有机化学是现代有机化学的主要理论基础,是当今有机化学中最富有活力的领域之一,它是建立在现代物理学和物理化学的基础上,用物理化学的、定量的、数学的方法来研究有机化学.     

利用跟踪TPR—GC和XRD技术考察LaNiO3的还原机理

钙钛矿型复合氧化物对许多反应具有较高的催化活性,它们被广泛地用作CO氧化的催化剂.陈水华等对SmMeO_3(Me:V、Cr、Mn、Fe、Co)和Tascon等对LaMeO_3(Me:V、Cr、Mn、Fe、Co、Ni)上CO催化活性评价说明,LnMnO_3和LnCoO_3(Ln=La、Sm)活性最好,而LaNiO_3则表现和LaCoO_3相似活性,由此可推断这些氧化物具有相似的催化性能.本文用TPR-GC和XRD考察了在还原气氛下,LaNiO_3的还原机理,这对研究其电、磁特性具有一定的指导意义.     

pH值对聚四氨基酞菁钴膜电化学和紫外光谱性质的影响

用循环伏安法在导电玻璃(ITO)和玻碳电极(GC)上制备了聚氨基酞菁钴(CoTAPc)修饰电极(CoTAPc/GC)。探讨了pH值对CoTAPc膜的光谱和电化学性质的影响，发现其氧化还原电位与pH值有线性关系，电催化活性也随酸度的增加而增加。CoTAPc膜的紫外吸收带变化与溶液pH值及在溶液中浸泡时间有关。     

无液接裸露式Ag/AgCl参比电极的研制及应用

提出了一种无液接裸露式Ag/AgC l参比电极制备方法,测试了该参比电极的稳定性、重现性、可逆性、响应时间、温度影响等因素。实验结果表明,该电极电位稳定在49 mV,响应时间在30 s以内时,具有重现性、可逆性好,使用寿命长,温度影响小等特点,可替代饱和甘汞和Ag/AgC l参比电极。     

C NMR spectra of cyclomercurated ferrocenylimines: Substituent effects and conformations in the ferrocenes

Three series of cyclomercurated ferrocenylimines (2-chloromercurio-ferrocenylimines) have been studied using ¹³C NMR spectroscopy. Good to excellent linear relationships have been found to exist between the chemical shifts of the carbon atoms in the ferrocenyl moiety and normal Hammett substituent constants σ_m and σ_p. The δ values of the iminyl carbon atoms show excellent linear correlations with the σ values. In three series of the ferrocenes, the sensitivity of the carbon atoms to the substituent effect is different, which is discussed in terms of the twist angle between the N-phenyl ring and the C---C=N---C plane. The relative sensitivity of the chemical shifts on different positions in ferrocenyl moiety to the substituent effect has also been presented.     

Synthesis,crystal structures and magnetic properties of transition metal dicyanamide complexes coordinated with pyridyl nitronyl nitroxides

Two novel complexes Ni(NITpPy)₂[N(CN)₂]₂ · 2H₂O (I) and Zn(NITpPy)₂[N(CN)₂]₂ · 2H₂O (II) (NITpPy = 2-(p-pyridyl)-4,4,5,5- tetramethylimidazoline-1-oxyl-3-oxide) were synthesized and characterized by infrared spectra, elemental analyses, and UV-Vis techniques. The crystal structures of both complexes have been determined by X-ray diffraction analysis. Both complexes are of centrosymmetric distorted octahedral co-ordination geometry in which metal ions are bound to two dicyanamide anions, two water molecules, and two radicals through the nitrogen atom of pyridine rings and show one-dimensional chain structure via hydrogen bonds. The magnetic properties of complexes I and II were investigated in the temperature range 5–300 K and discussed in detail. The two compounds exhibit weak intermolecular antiferromagnetic interaction. In complex II, the diamagnetic metal zinc just plays the role of a bridge. The article was submitted by the authors in English.     

甲壳素-壳聚糖对皂土悬浮液的絮凝

研究了三种摩尔质量大体相同而脱乙酰度分别为93%、78%和62%的甲壳素-壳聚糖在pH=3～6范围内对皂土悬浮液的絮凝性质, 并与非离子型絮凝剂聚丙烯酰胺作了比较, 证明含自由氨基的甲壳素-壳聚糖在酸性溶液中形成阳离子聚电解质后. 对带负电的皂土悬浮颗粒有很好的絮凝能力. 通过对上述三种聚合物的絮凝能力、在皂土颗粒表面的吸附量等测定, 认为絮凝中桥连机制起了主导作用, 但聚合物所带正电荷则有利于被皂土颗粒所吸附, 电中和还降低了颗粒间的静电排斥, 这都对桥连絮凝起了促进作用. 聚丙烯酰胺分子在水中不带电, 故当介质pH升高使皂土颗粒双电层变厚时, 絮凝能力迅速下降.     

Efficient dehalogenation of polyhalomethanes and production of strong acids in aqueous environments: water-catalyzed O--H-insertion and HI-elimination reactions of isodiiodomethane (CH2I-I) with water

A combined experimental and theoretical study of the ultraviolet photolysis of CH2I2 in water is reported. Ultraviolet photolysis of low concentrations of CH2I2 in water was experimentally observed to lead to almost complete conversion into CH2(OH)2 and 2HI products. Picosecond time-resolved resonance Raman spectroscopy experiments in mixed water/acetonitrile solvents (25%-75% water) showed that appreciable amounts of isodiiodomethane (CH2I-I) were formed within several picoseconds and the decay of the CH2I-I species became substantially shorter with increasing water concentration, suggesting that CH2I-I may be reacting with water. Ab initio calculations demonstrate the CH2I-I species is able to react readily with water via a water-catalyzed O--H-insertion and HI-elimination reaction followed by its CH2I(OH) product undergoing a further water-catalyzed HI-elimination reaction to make a H2C=O product. These HI-elimination reactions produce the two HI leaving groups observed experimentally and the H2C=O product further reacts with water to produce the other final CH2(OH)2 product observed in the photochemistry experiments. These results suggest that CH2I-I is the species that reacts with water to produce the CH2(OH)2 and 2HI products seen in the photochemistry experiments. The present study demonstrates that ultraviolet photolysis of CH2I2 at low concentration leads to efficient dehalogenation and release of multiple strong acid (HI) leaving groups. Some possible ramifications for the decomposition of polyhalomethanes and halomethanols in aqueous environments as well as the photochemistry of polyhalomethanes in the natural environment are briefly discussed.     

Calycilactone A, a novel hexacyclic alkaloid from Daphniphyllum calycillum

A novel Daphniphyllum alkaloid with a rearranged fused-hexacyclic ring system, calycilactone A, was isolated from the leaves of Daphniphyllum calycillum (Daphniphyllaceae), and the structure and relative stereochemistry of the new compound were elucidated on the basis of spectroscopic data.     

EFFECT OF MOLECULAR WEIGHT OF PDMS ON MORPHOLOGY AND MECHANICAL PROPERTIES OF PP/PDMS BLENDS

 A series of polydimethylsiloxane (PDMS) with varied molecular weights (Mw = 3  106, 1  106 and 0.5  106) were melt blended with PP to investigate the effect of PDMS molecular weight (MW) on the morphology and mechanical properties of PP/PDMS blends. Scanning electron microscopic (SEM) examination showed that the size of PDMS domains was dependent on the MW of PDMS. It was found that the lower the value of PDMS MW, the better dispersion of the PDMS domains in the PP matrix. Tensile and Izod impact tests revealed that the addition of PDMS with lower MW would lead to a more significant increase in impact strength of the blends compared with the blends with higher MW ones, while the influence of the molecular weight on tensile strengths of the blends was relatively small in the MW range studied. Differential scanning calorimetry (DSC) results also showed that the crystallization temperature of PP was increased with decreasing PDMS MW, indicating a better nucleation capability of lower MW of PDMS. Melting flow rate (MFR) measurements indicated that the processibility of PP could be enhanced by adding PDMS, and again the lower MW PDMS resulted in better data. Our work demonstrates that not only the processibility but also the mechanical properties of PP could be enhanced to a more significant degree by using low MW PDMS than the higher ones.