Table of Content

24 January 1997, Volume 13 Issue 1

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Articles

Surface Acidic Properties of Loaded Heteropoly Acid and Preparation of Dimethylether by Catalyzed Dehydration of Methyl Alcohol

HUA Rui-nian, WANG Yuan-hong, GONG Jian, ZU Wei, QU Lun-yu

1997, 13(1):  1-6. 

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The acidity and surface properties of H₄SiW₁₂ O₄₀ -Ti(SO₄)₂- La₂O₃ HZSM-5(HTLH) were investigated by means of TEM, TPD and IR spectra. The activity and selectivity of the product as a catalyst for methanol to dimethylether were studied. The results show that there are Brnsted and Lewis acid sites in HTLH and that the total acidity is concerned with the conversion of methanol and the yield of dimethylether. The catalytic capacity of the acid at 453 K is the best. Keggin unit [SiW₁₂ O₄₀]^4- deposits on the external HZSM-5 surface only, and it can not permeate through the HZSM-5 pore system.

Studies on the Electron Transfer Centers of Amino Oxidase Immobilized on Self Assembly Monolayer Using Electrochemical Methods

LI Jing-hong, CHENG Guang-jin, DONG Shao-jun

1997, 13(1):  7-13. 

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The direct electron transfer of amino oxidase on electrode surface based on self assembly technique occurs at 505 mV( vs . Ag/AgCl), indicating that copper atoms are the electron transfer centers and catalytic centers of amino oxidase.

Determination of Amino Acids as Their N-Hydroxy succinimidyl-3-indolylacetate Derivatives by Reversed phase HPLC

QIU Pei-hong, ZHANG Hua-shan, XU Guo-liang, CHENG Jie-ke

1997, 13(1):  14-20. 

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The present paper covers the reversed phase HPLC separation and determination of fourteen derivatized amino acids with a new reagent N- hydroxy-succinimidyl-3-indolylacetate(SIIA). The derivatives of the amino acids were eluted by a mobile phase of methanol water containing 10 mmol/L H₃cit Na₂HPO₄ buffer of pH 3.5 and 1.2 mmol/L tetrabutylammonium bromide on an ODS column. The detection limits were pmol level or so, respectively, when a signal to noise ratio was 3. The method was applied to the determination of amino acids in tea sample with satisfactory results.

Stereoselective Syntheses of Some β-D-1 Thioglycopyranosides and Bis( β-D-glycopyranosyl) Sulfides by Phase Transition Catalysis

YU Jian-xin, LIU Fang-min, SUN Wan-fu, LIU Yu-ting

1997, 13(1):  21-26. 

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The present paper covers the stereoselective syntheses of four 1 thiogalactopyranosides 1—4 and three thio disaccharides 5—7 through the PTC methods and their structures confirmed by means of elementary analysis, IR and NMR spectral data.

Studies on Thiosemicarbazides and Related Heterocycles(ⅩⅩⅤⅠ) ——Synthesis of 3-[5'-amino-1'-(4" chlorophenyl)-1', 2', 3'-triazol-4 yl]-4-aryl-1, 2, 4-triazoline-5-thiones

ZHANG Zi-yi, DONG Heng-shan, GUAN Zuo-wu

1997, 13(1):  27-33. 

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The treatment of 5-amino-1-(4'-chlorophenyl)-1, 2, 3-triazol-4-carbohydrazide with equimolecular aryl isothiocyanate gave new derivatives 1 _a—l . Twelve title compounds were obtained in 42% to 87% yields when compounds 1_a—l were respectively treated with sodium hydroxide aqueous solution(2 mol/L). The products of Dimroth rearrangement were not observed in the experiment. The structures of all the compounds were confirmed by means of IR, ¹H NMR, MS and elementary analysis.

Chemical Studies on the Glycosides in the Leaves of Oplopanax Elatus Nakai(Ⅳ)

WANG Guang-shu, XU Jing-da, MA Xiu-li, SUN Yun-xiu, LIU Ju-zheng

1997, 13(1):  34-38. 

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The further investigation of the chemical constituents of the leaves of Oplopanax elatus Nakai led to the isolation of two new triterpenoid saponins, named Cirensenosides M(1) and N(2). The structures of the two saponins were elucidated as 3α-hydroxyolean-9(11), 12-diene-28-oic acid 28-O-α-L-rhamnopyranosyl-(1→4)-β-D-glucopyranosyl-(1→6)-β-D-glucopyranoside(1) and 3-α-hydroxyolean 11, 13(18)-diene-28-oic acid 28-O-α-L-r hamnopyranosyl -(1→4) -β -D -glucopyranosyl(1→6) -β -D -glucopyranoside(2), respectively.

Effect of Steam on the Oxidative Coupling of Methane over La Ba System Catalysts

PIAO Hong, BI Ying-Li, ZHEN Kai-ji

1997, 13(1):  39-43. 

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The influence of steam on catalytic performance for the oxidative coupling of methane(OCM) over Ba²⁺ promoted La₂ O₃ catalysts was studied. It was shown that the presence of a suitable amount of steam led to a significant increase of the yield and selectivity to C₂ hydrocarbons, a decrease of selectivity to carbon monoxide and some increase of selectivity to carbon dioxide with increasing the amount of water in the feed was also observed. The activity and selectivity of the catalysts are more sensitive to the effect of steam with the variation of Ba²⁺ content in the catalysts at a relatively low temperature(650℃). The comparative experiments for OCM with methane-oxygen mixture diluted with nitrogen or steam were carried out in order to investigate the role of steam.

Ab initio Studies on Boron Clusters and Their Corresponding Boranes with T_d, O_h and I h Symmetries

YU Wei-zhou, ZHANG Ming-yu, SUN Chia-chung

1997, 13(1):  44-48. 

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The thermal stability and bonding characteristics of the larger boron clusters B n and their corresponding boranes with T_{d, Oh or Ih symmetries were studied by means of ab initio method. The results obtained from the calculation show that the clusters and boranes are all thermally stable to a different extent. The number of the skeletal bonding orbitals of Bn H^2-n satisfies the Wade's rule, but this kind of clusters need not be a complete triangular face polyhedron. The results also indicate that the larger neutral boranes Bn Hn may exist.}

A Theoretical Study of Nonlinear Second Order Optical Properties of Substituted Silanes

FENG Ji-kang, WANG Hai-chuan, WEI Jia-you, XIAO Chang-yong, XU Wen-guo, SUN Chia-chung

1997, 13(1):  49-58. 

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On the basis of ZINDO method and according to the sum-over-states(SOS) expression, the program is devised for the calculation of nonlinear second-order optical susceptibilites β_ijk and studying how different substituents on the phenyl ring attached to the atom silicon influence on the nonlinear second order optical properties of substituted silane series of molecules. The properties of (CH₃)₃Si——has been studied particularly. The effect of the length of silica chains on the calculated values has been studied too. The regularity summarized from the calculated results has been explained micromechanically.

Kinetic Analysis of an Enzyme-containing Polymer Modified Electrode

ZHU Kan, WU Hui-huang

1997, 13(1):  59-69. 

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A theoretical model for enzyme-entrapped conducting polymer modified electrodes is proposed and appropriate expressions are derived for the steady-state current response of the enzyme electrode. More attention has been paid to the role of conducting polymer in electron transfer and the effect of mass transport. On the basis of kinetic analysis, the performance and optimum design of the second and third generation enzyme electrodes are discussed.

Electron Ionization Mass Spectrometry of Some Ferrocenyl Thia-crown Ethers

SU Jing-zhe, JU Ying, WANG Tsong-Hui, LUO Zhao-fu, HU ANG Zai-fu

1997, 13(1):  70-76. 

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A new type of ferrocenyl thia crown ethers used as selective ligands to some poisonous metals was synthesized, and the features of their mass spectra in electron ionization mode were summarized as: (1) the strong molecular ion peaks; (2) a characteristic homologous ion series with sequential loss of C₂H₄S or C₂H₄O from M C₅H₅; (3) a new rearrangement reaction of Fe migration; (4) the uncommon loss of alcohol or thiol from the fragments of Fe rearrangement. Some typical fragmentation patterns were discussed in detail with the aid of exact mass measurement and MS/MS technique.

The Synthesis of Poly( ethylene oxide )-Block-Polybutylacrylate

LANG Mei-dong, ZHANG Guo, FENG Na, CHEN Xin-fang

1997, 13(1):  77-82. 

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Poly(ethylene oxide) containing azogroups(pre-PEO) was prepared by reacting azoisobutyronitrile (AIBN) with poly( ethylene glycol ) (PEG). The molecular weight of pre-PEO was depended on the reaction time, the ratio of PEG to AIBN and the molecular weight of PEG. Pre-PEO decomposed in the presence of butylacrylate (BA) monomer to form poly ethylene oxide block butylacrylate copolymers(PEO-b-PBA). The molecular weights of PEO-b-PBA and the homopolymer of PBA were proportional to the ratio of BA to pre-PEO. The purified block copolymers were charactherized using IR, ¹H NMR and GPC.

Coke Resistant Ni based Catayst for Partial Oxidation and CO₂-Reforming of Methane to Syngas

CHEN Ping, ZHANG Hong-bin, LIN Guo-dong, GUO Zhong-ping, TSAI Khi-rui

1997, 13(1):  83-85. 

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A Novel Thixotropic Phenomenon ——Complex Thixotropic Behavior

HOU Wan-guo, SUN De-jun, HAN Shu-hua, ZHANG Chun-guang, WANG Guo-ting

1997, 13(1):  86-88. 

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An Improved Preparation of 2, 5-Dimethoxy-tetrahydrofuran

LI Xiao-li, CHEN Qing-qi

1997, 13(1):  89-90. 

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The Active Oxygen Species for Oxidative Coupling of Methane over CeO₂/BaF₂ Catalyst by in Situ Confocal Microprobe Raman Spectroscopy

LONG Rui-qiang, WAN Hui-lin

1997, 13(1):  91-93. 

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