Chemical Research in Chinese Universities

Content of Chemical Research in Chinese Universities Vol.23 No.3(2007)

2007, 23(3): 0-0. doi:

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Synthesis of Coordination Polymers Using Different Maleic Acid Ligands under Hydrothermal Conditions

WANG Xiao-lan , WANG En-bo , XU Xin-xin

2007, 23(3): 245-249. doi:

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A novel coordination polymer, [Ni(mal)(1,10'-phen)(H₂O)]_n(1)(mal=malate, 1,10'-phen=1,10-phenanthroline) was synthesized using malic acid which was generated from maleic acid via hydrothermal reaction. Complex 1, which displays a two-dimensional supramolecular network, was formed by the addition reaction of Ni and maleic acid with water molecules. To our knowledge, several coordination polymers have been directly synthesized from malic acid, but these types of complexes have seldom been synthesized from maleic acid via hydrothermal reactions. When Ni(Ⅱ) ion was changed to Zn(Ⅱ) ion under the same condition, two-dimensional covalent complex 2[Zn₂(fma)₂(1,10'-phen)₂]_n(fma=fumatic acid) was formed. Furthermore, complex 2 exhibits intense photoluminescent property at room temperature.

Hydrothermal in situ Ligand Synthesis from 1,10-Phenanthroline-5,6-dione and Characterization of 1D Coordination Polymers [Co(bpdc)(H₂O)₃]·H₂O and [Cu(bpy)V₂O₆]

WANG Xiu-li, BI Yan-feng, LIN Hong-yan , LIU Guo-cheng

2007, 23(3): 250-253. doi:

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Hydrothermal treatment of MCl₂(M=Co or Cu), NH₄VO₃, and 1,10-phenanthroline-5,6-dione(pdon) resulted in the formation of a duplex coordination polymer [Co(bpdc)(H₂O)₃]·H₂O(bpdc=2,2'-bipyridine-3,3'-dicarboxylate) and a chain-like coordination polymer [Cu(bpy)V₂O₆](bpy=2,2'-bipyridine). X-ray single-crystal structural analysis shows that under hydrothermal conditions and in the presence of different transition metals, the organic reagent pdon was transformed in situ into bpdc and bpy, respectively. Mechanism of the in situ ligand synthesis reaction has been discussed.

Protein Adsorption onto Nanosized Hydroxyapatite Particles for Controlled Drug Release

WANG Bo , TENG Li-rong , WANG Chun-yan , MENG Qing-fan , ZHAO Ling-zhi , GAO Bo

2007, 23(3): 254-257. doi:

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Nanosized hydroxyapatite(nsHAp) was synthesized to examine its possibility as a controlled release carrier of protein. To achieve effective protein release from nanosized hydroxyapatite, the study of the adsorptive properties of protein on nsHAp and different influence parameters such as pH, calcium, and phosphate concentrations during the adsorption process is necessary. Ovalbumin(OVA) was selected as the model of growth factors. The results show that the amount of OVA adsorbed onto nsHAp in acetic buffer(pH=3.6) is more than that in acetic buffer(pH=5.6) because of the electric interaction. The amount of OVA adsorption in phosphate buffer solution(PBS) is smaller than that in acetic buffer because of surface complexation and surface hydroxylation. The presence of Ca²⁺ dramatically increases the adsorbed amount of OVA in acetic buffer on maintaining the same pH. Meanwhile, the release kinetics of OVA adsorbed onto nsHAp(nsHAp-OVA) was also examined. The amount of released OVA in PBS(pH=5.6) was significantly smaller than that released in solution of pH=7.0. All the results suggest that nanosized hydroxyapatite particles could be successfully used as controlled released carrier of protein.

Synthesis and Characterization of Pr(DPM)₃ Served as Precursor for MOCVD

LIU Ming-fei, HU Yong-xing, JIANG Yin-zhu, GAO Jian-feng, WANG Yan-yan , MENG Guang-yao

2007, 23(3): 258-262. doi:

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Praseodymium β-diketone chelate, Pr(DPM)₃[DPM=2,2,6,6-tetramethyl-3,5-heptanedionato], was successfully synthesized from the inorganic salt praseodymium chloride and HDPM(2,2,6,6-tetramethyl-3,5-heptane-dione) in an ethanol/aqueous solution followed distillation at low pressure and recrystallization from toluene. The physical and thermal properties of the chelate, including volatility, stability, and thermal decomposition, were investigated by elemental analyses, ¹H NMR spectroscopy, XRD, TG/DTG/DTA analysis, infrared spectroscopy, and mass spectroscopy. The chelate with high purity prepared by the authors of this study also shows sufficient volatility and stability in inert gases, which could be used as the precursor for metal-organic chemical vapor deposition(MOCVD).

Hybrid Tungstocuprate [Cu(2,2'-bpy)₃]₂H₄[CuW₁₂O₄₀]·6H₂O Based on Keggin Polyoxoanion [CuW₁₂O₄₀]^6- with CuⅡas Heteroatom

WANG Jing-ping, MA Peng-tao, LI Jie , NIU Jing-yang

2007, 23(3): 263-267. doi:

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A novel hybrid tungstocuprate(Ⅱ) [Cu(2,2'-bpy)₃]₂H₄[CuW₁₂O₄₀]·6H₂O(2,2'-bpy=2,2'-bipyridine) was synthesized via hydrothermal method and characterized using elemental analyses, IR, UV, XPS, TG-DSC, EPR, and X-ray single crystal diffraction. The structural analysis shows that the complex consists of an unusual Keggin-type polyoxoanion [CuW₁₂O₄₀]^6- and a pair of chiral complex cations [Cu(2,2'-bpy)₃]⁺ together with four protons and six crystallization water molecules, and the Keggin polyoxoanion is connected with [Cu(2,2'-bpy)₃]⁺ via multiple C—H…O hydrogen bonds resulting in a dimer.

Rapid Determination of HAAs Formation Potential of the Reaction of Humic Acid with Chlorine or Chlorine Dioxide

ZHU Zhi-liang, GE Yuan-xin, ZHANG Rong-hua, MA Hong-mei , ZHAO Jian-fu

2007, 23(3): 268-272. doi:

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On the basis of gas chromatography(GC) coupled with a short capillary column and an electron capture detector(ECD), a simple and rapid method for the determination of five haloacetic acids(HAAs) in drinking water was developed by the optimization of derivation conditions and the modification of gas chromatographic program. HAAs formation potential(HAAFP) of the reaction of humic acid with chlorine was determined via this method. The major advantages of the method are the simplicity of chromatographic temperature program and the short run time of GC. Dichloroacetic acid(DCAA) and Trichloroacetic acid(TCAA), which were detected in the determination of HAAFP, were rapidly formed in the first 72 h of the reaction of humic acid with chlorine. HAAFP of the reaction of humic acid with chlorine increased with the increase in the concentrations of humic acid and chlorine. The average HAAFP of the reaction of humic acid with chlorine was 39.9 μg/mg TOC under the experimental conditions. When the concentration of humic acid was 4 mg/L, the concentration of HAAs, which were produced in the reaction of humic acid with chorine, may exceed MCL of 60 μg/L HAAs as the water quality standards for urban water supply of China and the first stage of US EPA disinfection/disinfection by-products(D/DBP) rule; when the concentration of humic acid was 2 mg/L, the concentration of HAAs may exceed MCL of 30 μg/L HAAs for the second stage of US EPA D/DBP rule. When humic acid was reacted with chlorine dioxide, only DCAA was detected with a maximum concentration of 3.3 μg/L at a humic acid content of 6 mg/L. It was demonstrated that the substitution of chlorine dioxide for chorine may entirely or partly control the formation of HAAs and effectively reduce the health risk associated with disinfected drinking water.

Degradation of Organic Pollutants in Water by Catalytic Ozonation

LI Xin , YAO Jun-hai , QI Jing-yao

2007, 23(3): 273-275. doi:

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Different series of transition metal catalysts supported on Al₂O₃ were prepared by the impregnation method. The catalytic activity was measured in a batch reactor with ozone as the oxidizing reagent. The experimental results indicate that Cu/Al₂O₃ has a very effective catalytic activity during the ozonation of organic pollutants in water. The optimum conditions for preparing Cu/Al₂O₃ were systematically investigated with the orthogonal testing method. Furthermore, the results also show that the surface properties of catalyst are not compulsory for effective oxidation.

Efficient Synthesis of Octalone

ZHANG Chen, CHEN Jin-chun, ZHENG Guo-jun , LI Yu-lin

2007, 23(3): 276-279. doi:

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A highly efficient and convergent approach for the synthesis of octalone 1, the focal intermediate for the synthesis of several sesquiterpenoids, was developed based on the cationic cyclization strategy of the functionalized oxabicyclic template 5.

Syntheses and Biological Activities of Ethyl N-Hydroxy-N-(substituted)phenyloxamates as KARI Inhibitors

WANG Bao-lei, LI Zheng-ming, LI Yong-hong , WANG Su-hua

2007, 23(3): 280-283. doi:

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Nine ethyl N-hydroxy-N-(substituted)phenyloxamates(2a—2i), based on the structure of the KARI inhibitor IpOHA, were synthesized. Their structures were established on the bases of ¹H NMR, IR, ESI-MS and elemental analyses. Among the nine compounds, four show in vitro inhibitory activity on rice KARI, with 2c and 2g[K_i values of (35.2±4.9) and (49.4±6.3) μmol/L] having similar activity to the precursor of IpOHA(A, K_i=34.1±6.7 μmol/L). The results will be helpful to further molecular design of more potent KARI inhibitors.

Syntheses and Bioactivities of 4-Ar-2-oxo-glutaric Acids

CHEN Qiu-yun , ZHANG Rong-xian , LIU Qing-shan , Schofield Christopher

2007, 23(3): 284-288. doi:

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Fourteen novel compounds were synthesized and characterized by using NMR and ESI-MS methods. The bioactivities of the four novel 4-Ar-2-oxo-glutaric acids were studied by using the LC-MS method. The experimental results show that 3-nitrobenzyl-2-oxo-glutaric acid is a mild inhibitor for the hydroxylation reaction catalyzed by PHD2. The decarboxylated peak for 3-fluorobenzyl-2-oxo-glutaric acid was observed by using the negative LC-MS method, indicating that it can be used as a mild cosubstrate to replace 2-OG, but this is possible only in the presence of the prime peptide CODD 19 mer.

Expression and Characterization of Catalytic Domain of T Cell Protein Tyrosine Phosphatase(ΔTC-PTP)Immunohistochemical Study of ΔTC-PTP Expression in Non-small Cell Lung Carcinomas

ZHU Zhi-cheng , SUN Mei , ZHANG Xing-yi , LIU Ke-xiang , SHI Dong-lei , LI Jin-dong , SU Ji-quan , XU Yue-chi , FU Xue-qi

2007, 23(3): 289-296. doi:

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This study objective was to express and characterize the catalytic domain of the human T cell protein tyrosine phosphatase(ΔTC-PTP) and to study immunohistochemically the expression of ΔTC-PTP in human non-small cell lung cancers. ΔTC-PTP gene was PCR amplified with the cDNA of human TC-PTP as template, and cloned into the pT7 expression vector. The recombinant pT7-ΔTC-PTP was expressed in E.coli Rosetta(DE3) host cells and purified. The enzymatic characteristics of ΔTC-PTP including enzyme activity and kinetics assay were measured. The antiserum was prepared by immunizing rabbit with the purified recombinant ΔTC-PTP. Rabbit polyclonal antibody against ΔTC-PTP was purified by PVDF immobilized antigen affinity chromatography. Immunohistochemical staining of lung cancer tissues was performed with antibody against ΔTC-PTP protein. ΔTC-PTP gene was correctly cloned, expressed, and purified. The recombinant ΔTC-PTP had a highly catalytic activity of PTPase. Squamous cell lung carcinoma showed a significantly higher expression rate of ΔTC-PTP(76.92%, 10/13) than adenocarcinoma(57.14%, 4/7) and normal lung tissue(20%, 1/5). This study represents the first demonstration that ΔTC-PTP is highly expressed in human squamous cell lung carcinomas. In addition, this study provides an important basis for further studying the biological function of TC-PTP and its relationship with lung carcinomas and other diseases.

Reduced Bone Mineral Density and Bone Metabolism in Aquaporin-1 Knockout Mice

WU Qing-tian, , MA Qing-jie , HE Cheng-yan , WANG Cai-xia , GAO Shi , HOU Xia , MA Tong-hui

2007, 23(3): 297-299. doi:

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An overt phenotype of aquaporin-1 knockout(AQP1 ko) mice is growth retardation, suggesting possible defects in bone development and metabolism. In the present study, we analyzed the bone mineral density(BMD), bone calcium and phosphorus contents, and bone metabolism in an AQP1 ko mouse model. The BMD of femurs in AQP1 ko mice was significantly lower than that of litter-matched wildtype mice as measured by dual energy X-ray absorptiometry. Consistently, the contents of bone total calcium and phosphorus were also significantly lower in AQP1 ko mice. The reduced BMD caused by AQP1 deficiency mainly affect male mice. Bone metabolic activity, as indicated by ⁹⁹mTc-MDP absorption measurements, was remarkably reduced in AQP1 ko mice. These results provide the first evidence that AQP1 play an important role in bone structure and metabolism.

Design and Synthesis of Glycosylated Aromatic Nitrogen Mustard Derivatives

LIU Tie-mei , WANG Shu-sheng , ZHU Guang-ze , LI Ming-yang , ZHANG Li-ping

2007, 23(3): 300-302. doi:

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Antibody-directed enzyme prodrug therapy(ADEPT) is a new strategy for the treatment of cancer that has arisen in recent twenty years, the main merits of which are that it can improve the selectivity of anticancer drugs and reduce the side effects in remote tissue. In the present study, two prodrugs-glycosylated aromatic nitrogen mustard derivatives were synthesized. Glucose and lactose were converted into glycosyl donors-trichloroacetimidate; the obtained glycosyl donors were glycosylated with p-nitrophenol(glycosyl donors) to form β-glucosyl p-nitrobenzene and β-lactosyl p-nitrobenzene that were protected by acetyl in a stereoselective manner; the two products were reduced by zinc dust and then treated with ethylene oxide, afforded two glycosylated nitrogen mustard derivatives that were protected by acetyl; the last step was to deacetylate and then afforded the two target compounds that could be used as prodrugs of ADEPT for further Anti-tumor research.

Modification of Sugar Chains in Glycoalkaloids and Variation of Anticancer Activity

LI Sheng-yu, HE Da-jun, ZHANG Xu, NI Wei-hua, ZHOU Yi-fa , ZHANG Li-ping

2007, 23(3): 303-309. doi:

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To study the effect of the sugar chains in glycoalkaloids against cancer cells, 6-O-sulfated solamargine and acid-catalyzed hydrolytic products of α-solamargine and α-solasonine were prepared. The sulfation at O-6 of solamargine was proceeded in five steps. The 6-OH group was first selectively protected with DMT-Cl, and then the secondary hydroxyl groups on the sugar ring were acetylated. After the protective group DMTr was removed, the free 6-OH group was sulfated. Finally, the acetyl groups were removed to give 6-O-sulfated solamargine in a good yield. The hydrolyses of solamargine and solasonine were performed in diluted hydrogen chlorede. Three and two hydrolyzed products were obtained from solamargine and solasonine, respectively. The antiproliferative activities against HCT-8 tumor cells of two glycoalkaloids and their derivaties were examined via a MTT assay. The results show that α-solamargine and α-solasonine exhibit strong cytotoxic activities with an IC₅₀ of 10.63 and 11.97 μmol/L, respectively, wheras their derivaties seem to be less activities.

Construction and Characterization of a cDNA Expression Libraryfor the North American Ginseng Root Tissues

WANG Ying , WANG Kun , BAO Yong-li , WU Yin , MENG Xiang-ying , LI Yu-xin

2007, 23(3): 310-313. doi:

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The root of Panax ginseng plant undergoes a specific developmental process to become a biosynthesis and accumulation tissue for ginsenosides. To identify and analyze genes involved in the biosynthesis of ginsenoside, we constructed and characterized a full-length cDNA library for 6-year-old North American ginseng. The titer of primary cDNA library is 1.2×10⁶ pfu/mL, the titer of amplified library is 2.6×10¹⁰ pfu/mL and the rate of recombinant is above 86%. The insert size ranges from 0.3 to 2.0 kb. Sequencing results show that 18 of 58 genes are high homologous to the genes(GBR5, GBR3 and GBR1) known in GenBank, which are involved in biosynthesis of ginsenoside in North American ginseng plant; 16 of 58 genes are novel genes. The full-length cDNA library of North American ginseng root tissues is essential for the cloning of genes known and it is also an initial key for the screening and cloning of new genes.

Immunogenicity and Efficacy of Liposome-encapsulated Influenza Split Vaccine in BALB/c Mice

QI Feng-chun , WANG Chun-yi , WANG Ya-jun , ZHANG Xue-mei , ZHANG Yan , SUI Bo , LI Xiao-bo , SHENG Jun

2007, 23(3): 314-318. doi:

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The cellular immunity of current influenza split vaccine is relatively low. It is necessary to develop a novel vaccine to improve the cellular immunity. The authors of this study prepared liposome-encapsulated influenza split vaccine and tested it in BALB/c mice. The mice were immunized once with 4 μg of haemagglutinin of monovalent A/New Caledonia/20/99(H1N1) encapsulated with liposomes or the split virus vaccine only through intrastomach injection. In a comparative study, it was observed that the liposome-encapsulated vaccine elicited a higher neutralizing antibody response, more effectively stimulated spleen cell proliferation, increased cell subsets like CD4⁺ and CD4⁺/CD8⁺, and triggered IL-4 and IFN-γ production.

High-throughput Screening of the Enantioselectivity of Hyperthermophilic Mutant Esterases from Archaeon Aeropyrum pernix K1 for Resolution of (R,S)-2-Octanol Acetate

ZHANG Gui-rong, GAO Ren-jun, ZHANG Ai-jun, RAO Lang , CAO Shu-gui

2007, 23(3): 319-324. doi:

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To identify the desired hyperthermophilic variants within a mutant esterase library for the resolution of (R,S)-2-octanol acetate, a simple, reliable, and versatile method was developed in this study. We built a screening strategy including two steps, first we selected agar plate with substrate to screen the enzymatic activity; secondly we used a pH indicator to screen the enantioselectivity. This method could rapidly detect favorable mutants with high activity and enantioselectivity. A total of 96.2% of tedious screening work can be precluded using this screening strategy. It is an effective screening for alkyl ester and can be applied to relative screening researches. The four improved mutants were screened from the mutant esterase library. Their enantioselectivities, activities, and structures were investigated at different temperatures.

Preparation and Kinetics of a Novel Glutathione Peroxidase MimicSelenium-modified Hyaluronic Acid

CHEN Jia, HONG Shui-sheng, AN Yang, JIANG Guang-zhi, ZHANG Bo-xun, FANG Xiang-yang, LIU Lan-ying , TENG Li-rong

2007, 23(3): 325-328. doi:

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A selenium-modified hyaluronic acid(HA) compound(SeHA) was synthesized as a mimic of glutathione peroxidase(GPX). IR and NMR spectra of SeHA predict that the —CH₂OH group of the N-acetyl-D-glucosamine in HA was modified by group —SeH. There are averagely 152 —SeH groups in one SeHA molecule. The GPX activities are 103.88, 32.15 and 152.71 U/μmol, respectively, when the substrates were H₂O₂, BuOOH and CuOOH. Ping-pong mechanism was observed in the steady-state kinetic studies of the reactive oxygen species(ROS) consuming reaction. Result of reactions of SeHA with free radical capturer 2,6-di-tert-butyl-4-methylphenol(BHT) shows that the catalysis is based on a non-free radical-mechanism and the SeHA can not be inhibited by iodoacetate, an enzyme inhibitor.

Immunogenicity of Lyophilized MVA Vaccine for HIV-1 in Mice Model

ZHANG Yi-zhe, JIANG Chun-lai, YU Xiang-hui, LOU Chao-ping, ZHAO Dong-hai, WU Yong-ge, JIN Ying-hua, LIU Cheng-shan , KONG Wei

2007, 23(3): 329-332. doi:

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Highly attenuated modified vaccinia Ankara(MVA) is sensitive to repeat freeze-thaw cycle and easy to lose activity. In order to make the activity of MVA vaccine remain stable during its manufacturing, storage, and administration, the lyophilization as a good option could be resorted to; through screening, the right stabilizer composition and its production procedure were obtained. The final moisture content of freezing-dried recombinant MVA-HIV vaccine was lower than 3%. It can be reconstituted quickly and shows regular physical appearance and stable potency. In vivo functional experiment, mice were divided randomly into the liquid vaccination group, the lyophilized vaccination group, and the control group. Having been DNA vaccine priming, the mice were boosted with a dose of 10⁷ pfu MVA-HIV vaccine, which produced indistinguishable antibody titer and cytotoxic T-lymphocyte(CTL) level compared with those of liquid vaccination group(P>0.05). These results demonstrate that lyophilized MVA vaccine can induce high immunogenicity in mice.

Kinetics and Mechanism of Iridium(Ⅲ)-Catalyzed Oxidation of Ethanol Amine by Cerium(Ⅳ) in Sulfuric Acid Media

ZHAI Yong-qing, LIU Hong-mei, YANG Lin, YANG Guo-zhong, SONG Wen-yu , LIU Yu-kai

2007, 23(3): 333-338. doi:

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In this study, the kinetics and mechanism of the iridium(Ⅲ)-catalyzed oxidation of ethanol amine(EAN) by cerium(Ⅳ) in a sulfuric acid medium was investigated using titrimetric technique of redox in a temperature range of 298—313 K. It was found that the reaction is of first order with respect to Ce(Ⅳ) and Ir(Ⅲ), and a positive fractional order with respect to EAN. It was also found that the pseudo-first-order([EAN][Ce(Ⅳ)]) rate constant k_obs decreases with the increase of [H⁺] and [HSO₄^-]. Under the protection of nitrogen gas, the reaction system can initiate the polymerization of acrylonitrile, indicating the generation of free radicals. On the basis of the experimental results, a suitable mechanism was proposed. From the dependence of k_obs on the concentration of hydrogen sulfate, Ce(SO₄)₂ was found to be the kinetically active species. The rate constants of the rate-determining step together with the activation parameters were evaluated.

Interaction of Biologically Active Molecules with Sulfur-modified Gold Surface

DING Xue-feng , YANG Gui-fu , WANG Xiao , WANG Zi-chen , LIN Hai-bo

2007, 23(3): 339-342. doi:

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The immobilization of cytochrome c or horseradish peroxidase at the sulfur-modified gold electrode exhibits a ra-pid electron transfer behavior because of its specific orientation on the electrode surface and the interaction between cytochrome c or horseradish peroxidase and sulfur-modified on the surface of the Au electrode.

Crystal Structure and DFT Studies of a Triazole Derivative: 4-(2-Hydrobenzylideneamino)-3-(1,2,4-triazol-4-yl-methyl)1H-1,2,4-triazole-5(4H)-thione

LI Wei-hua , ZHANG Shu-fang , LIU Fa-qian , HOU Bao-rong

2007, 23(3): 343-348. doi:

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A novel triazole derivative 4-(2-hydrobenzylideneamino)-3-(1,2,4-triazol-4-ylmethyl)-1H-1,2,4-triazole-5(4H)-thione(1) was synthesized and characterized using elemental analysis, FTIR, and ¹H NMR, and its crystal structure was determined via X-ray single crystal diffraction analysis. Crystal data: monoclinic, P2(1)/c, a=0.83335(9) nm, b=1.49777(16) nm, c=1.14724(12) nm, β=107.990(2)°, D=1.470 Mg/m³, and Z=4. The geometries and the vibrational frequencies were determined using the density functional theory(DFT) method at the B3LYP/ 6-31G* level. To demonstrate the accuracy of the reaction route of compound 1, one of the important intermediates was also tested using the same method. The structural parameters of the two compounds calculated using the DFT study are close to those of the crystals, and the harmonic vibrations of the two compounds computed via the DFT method are in good agreement with those in the observed IR spectral data. The thermodynamic properties of the title compound were calculated, and the compound shows a good structural stability at normal temperature. The test results of biological activities show that it has a certain bactericidal ability.

Preparation and Catalytic Application of Novel Water Tolerant Solid Acid Catalysts of Zirconium Sulfate/HZSM-5

JIANG Ya-jie , JUAN Joon Ching , MENG Xiu-juan , CAO Wei-liang , YARMO Mohd Ambar , ZHANG Jing-chang

2007, 23(3): 349-354. doi:

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Esterification of acrylic acid(AA) to produce AA esters has widespread application in the chemical industry. A series of water tolerant solid acid catalysts was prepared, and characterized by XRD, nitrogen adsorption, TGA-DTA, XPS, and ammonia adsorption FTIR. The effects of Si/Al ratio, zirconium sulfate(ZS) loading on HZSM-5 and calcination temperature on the esterification were investigated. When 20%(mass fraction) ZS is loaded on HZSM-5, the conversion of AA reaches 100%. XRD analysis indicates that ZS is highly dispersed on HZSM-5 because no crystalline structure assigned to ZS is found. Catalytic activity and hydrophobicity of ZS supported on HZSM-5 are higher compared with those of parent ZS or HZSM-5. Results show that this kind of novel catalysts is an efficient water tolerant solid acid catalyst for esterification reactions.

Ab Initio Calculations on Halogen Bond Between N—Br and Electron-donating Groups

WANG Yan-hua , CHEN Xue-song , ZOU Jian-wei , YU Qing-sen

2007, 23(3): 355-359. doi:

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Ab initio calculations of complexes formed between N-bromosuccinimide and a series of electron-donating groups were performed at the level of MP2/Lanl2DZ* to gain a deeper insight into the nature of the N—Br halogen bonding. For the small complexes, H₃C—Br…NH₃ and H₂N—Br…NH₃, the primary calculation has demonstrated that the N—Br in H₂N—Br…NH₃ can form a much stronger halogen-bonding complex than the C—Br. A comparison of neutral hydrogen bond complex series reveals that the electron-donating capacities of the atoms decrease in the order, N>O>S; O(sp³)>O(sp²), which is adequate for the C—Br halogen bonding. Interaction energies, in conjunction with the geometrical parameters show that the affinitive capacity of trihalide anions X₃^- with N-bromosuccinimide are markedly lower than that of the corresponding X^-with N-bromosuccinimide, even lower than those of neutral molecules with N-bromosuccinimide. AIM analyses further confirmed the above results.

Crystalline Morphology and Crystallization Characteristics of In-situ Blends of Anionic Polyamide 6 with Noncrystallizable Semiaromatic Polyamide Copolymer

WANG Xiao-chun , ZHENG Qiang , YANG Gui-sheng

2007, 23(3): 360-365. doi:

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A noncrystallizable semiaromatic polyamide copolymer(NSAP) was dissolved in molten caprolactam, and PA6/NSAP blends were produced in-situ via the anionic ring-opening polymerization of caprolactam. The presence of a single loss tangent(tanδ) peak measured by means of dynamic mechanical analysis(DMA) proves the miscibility between PA6 and NSAP in the blends. It was found that there existed drastic changes in the crystallographic form and crystallization kinetics for the in-situ blends, e.g., when 20% NSAP was added, nearly all crystallites existed in the γ form and the crystallization could hardly occur upon cooling even at a rate of 2.5 ℃/min. Moreover, cold crystallization appears during the subsequent heating, and its melting point is 40 ℃ lower than that of the virgin system. On the other hand, the size of the spherulites only decreases modestly. It is suggested that the introduction of irregular stiff segments originated from NSAP into PA6 macromolecule chain, which resulted from transamidation during the polymerization play a dominant role in the drastic change of crystallization kinetics and the resultant morphology of the in-situ blends.

Formation of Ultrafine Apatite Fibers by Sol-gel/Electrospinning

DING Ya-mei, YUAN Xiao-yan, ZHAO Jin, GUO Wan-chun , WANG Xiu-kui

2007, 23(3): 366-369. doi:

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Ultrafine apatite fibers were prepared by electrospinning of sol-gel precursor/poly(vinyl pyrrolidone)(PVP) solutions followed by subsequent calcination. The as-electrospun and calcinated fibers were observed under a scanning electron microscope and an optical polarizing microscope. Results show that the morphology and the diameter of as-electrospun fibers strongly depend on the viscosity and the surface tension of sol-gel precursor/PVP solutions. After calcination, the smooth as-electrospun fibers shrink and the fiber diameter decreases because of the removal of the polymer. The chemical evolution upon the transformation of the precursor from a gel to the final apatite fibers was investigated by thermogravimetric-differential thermal analysis, X-ray diffraction, and Fourier transform infrared spectroscopy. It is thus suggested that the crystalline structure of the calcined fibers is largely influenced by the calcination temperature. After being calcined at 600 ℃, the apatite fibers with a diameter of about 280 nm containing β-tricalcium phosphate were obtained.

Crystallization Kinetics and Melting Behavior of PA1010/Ether-based TPU Blends

ZHANG Shu-ling, ZHAO Yan, SUN Xiao-bo, JIANG Zhen-hua, WU Zhong-wen , WANG Gui-Bin

2007, 23(3): 370-373. doi:

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Polyamide 1010(PA1010)/thermoplastic poly(ether urethane) elastomer(ether-based TPU) blends were prepared via melt extrusion. The crystallization kinetics and melting behavior of PA1010/ether-based TPU blends were systematically investigated using differential scanning calorimetry. The crystallization kinetics results show that the addition of ether-based TPU hinders the crystallization of PA1010, and the hindrance effect increases with the increase of the concentration of ether-based TPU. Both pure PA1010 and PA1010/ether-based TPU blends exhibit double melting peaks in the process of nonisothermal crystallization. The double melting peaks change differently with the variation of cooling rate and blend composition. The cooling rate only influences the lower melting peak; however, the blend composition influences not only the lower melting peak but also the higher melting peak. The reason for the phenomenon must be the interaction between the two compositions.

Synthesis of Dimethyl Carbonate from CO₂, Methanol, and Epoxides Using Re(CO)₅Cl/K₂CO₃ as Catalyst System

JIANG Jia-li , HUA Rui-mao

2007, 23(3): 374-376. doi:

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