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Study on the synthesis and performance of 3,3'-azobis (6-amino-1,2,4,5-tetrazine)
XU Songlin, YANG Shiqing, ZHANG Wei, ZHANG Xingao
Front. Chem. China. 2007, 2 (2): 113-117.
https://doi.org/10.1007/s11458-007-0023-7
The synthesis of high-nitrogen energetic material 3,3´-azobis (6-amino-1,2,4,5-tetrazine) (DAAT) from 3,6-bis (3,5-dimethylpyrazol-1-yl)-1,2,4,5-tetrazine by a four-step reaction is described. The thermal properties of DAAT
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Evaluation of antioxidants using oxidation reaction rate constants
SHI Yan, ZHAN Xiancheng, MA Lie, LI Linli, LI Chengrong
Front. Chem. China. 2007, 2 (2): 140-145.
https://doi.org/10.1007/s11458-007-0029-1
An evaluation method for the capacity of antioxidants to protect drugs against oxidation is presented. As a new viewpoint, to determine the priority of the competitive oxidations between the antioxidant and the protected drug, and to compare the drug-protection capacity of antioxidants, it is important to determine their oxidation rate constants using chemical kinetics instead of standard oxidation (or reduction) potentials. Sodium sulfite, sodium bisulfite and sodium pyrosulfite were used as models for the determination of oxidation reaction rate constants in aqueous solutions. In the experiments, sufficient air was continually infused into the solution to keep the concentration of dissolved oxygen constant. The residual concentrations of the antioxidants were determined by iodimetry, and the concentration of dissolved oxygen by oxygen electrode. The data were fitted by linear regressions to obtain the reaction rate constants. It was found that the degradation of sodium sulfite, sodium bisulfite or sodium pyrosulfite obeyed pseudo zero-order kinetics in the buffer solutions. Because of the ionization equilibrium, these three antioxidants have the same ion form in solutions at a definite pH value and therefore their apparent rate constants were essentially the same. The average apparent rate constants of the three antioxidants at 25?C are (1.34?0.03)?10-3 at pH 6.8, (1.20?0.02)?10-3 at pH 4.0 and (6.58?0.02)?10-3 mol °L-1° h-1 at pH 9.2, respectively.
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Highly sensitive choline biosensor based on carbon nanotube-modified Pt electrode combined with sol-gel immobilization
SONG Zhao, ZHAO Zixia, QIN Xia, HUANG Jiadong, SHI Haibin, WU Baoyan, CHEN Qiang
Front. Chem. China. 2007, 2 (2): 146-150.
https://doi.org/10.1007/s11458-007-0030-8
A novel amperometric choline biosensor has been fabricated with choline oxidase (ChOx) immobilized by the sol-gel method on the surface of multi-walled carbon nanotubes (MWCNT) modified platinum electrode to improve the sensitivity and the anti-interferential property of the sensor. By analyzing the electrocatalytic activity of the modified electrode by MWCNT, it was found that MWCNT could not only improve the current response to H2O2 but also decrease the electrocatalytic potential. The effects of experimental variables such as the buffer solutions, pH and the amount of loading enzyme were investigated for the optimum analytical performance. This sensor shows sensitive determination of choline with a linear range from 5.0×10-6 to 1.0×10-4 mol/L when the operating pH and potential are 7.2 and 0.15 V, respectively. The detection limit of choline was 5.0×10-7 mol/L. Selectivity for choline was 9.48 μA · (mmol/L)-1. The biosensor exhibits excellent anti-interferential property and good stability, retaining 85% of its original current value even after a month. It has been applied to the determination of choline in human serum.
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Investigation of ultraviolet curable waterborne polyurethane acrylate dispersion based on hydroxyl-terminated polybutadiene
NIU Zhenbin, ZHANG Xingyuan, DAI Jiabing, ZHANG Heping
Front. Chem. China. 2007, 2 (2): 151-155.
https://doi.org/10.1007/s11458-007-0031-7
A new kind of ultraviolet (UV) curable waterborne polyurethane acrylate dispersion was synthesized based on hydroxyl-terminated polybutadiene (HTPB), poly-(propylene glycol) (PPG), isophorene diisocyanate (IPDI), 2-hydroxy ethyl acrylate (HEA) and dimethylol propionic acid (DMPA) after neutralizing by triethylamine (TEA). 2-Hydroxy-1-[4-(2-hydroxyethoxy) phenyl]-2-methyl-lpropanone (Irgacure 2959) was used as a photoinitiator and deionized water as a diluent. Fourier transform infrared (FTIR) analysis was used to identify the chain structure of the UV-curable polyurethane prepolymer based on HTPB and the curing process. Effects of relative content of HTPB and PPG on emulsion stability, resistance to water and ethanol, thermal stability, compatibility of soft and hard segment, as well as the mechanical property of the cured film were investigated.
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Studies on solid state synthesis and the oxygenation property of cobalt (II) Schiff base (vanilline polyamine) complexes
XIAO Furong, CHEN Lu, WANG Jide, WU Ronglan, YUE Fan, LI Jing
Front. Chem. China. 2007, 2 (2): 169-173.
https://doi.org/10.1007/s11458-007-0034-4
Three new cobalt complexes were synthesized by solid-state reaction at room temperature and the resultant Co complexes reacted with two equivalent oxygen molecules at room temperature to produce the oxygenated complexes [Co° (L1)2 °(O2)2](NO3)2 °2H2O (L1 = N, N´-bis(4-hydroxyl-3-methoxy-benzyl)-diethylenetriamine), [Co ° (L2)2° (O2)2] (NO3)2 ° 2H2O (L2 = N, N´-bis(4-hydroxyl-3-methoxybenzyl)-triethylenetetramine), and [Co ° (L3)2 ° (O2)2](NO3)2 °2H2O (L3 = N, N´-bis(4-hydroxyl-3-methoxy-benzyltetraethylenepentamine). The oxygenated complexes were characterized by elemental analysis, IR (Infrared), 1H-NMR (Nuclear Magnetic Resonance), and UV-Vis (Ultraviolet Visual) spectrometry, and TG/DTA (Thermogravimetry/Differential Thermal Analysis) analysis, and molar conductance. The coordinated oxygen contents in the oxygenated com plexes were also determined by weight method. It was supposed that only one O2 molecule coordinated to the Co ion forming a superoxo type oxygenated complex.
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Synthesis and characterization of inexpensive 3-Nε-benzyloxycarbonyl-L-lysyl-morpholine-2,5-dione
YAO Junyan, YANG Qingfang, FAN Xiaodong, WANG Ning, GUO Baohui
Front. Chem. China. 2007, 2 (2): 183-187.
https://doi.org/10.1007/s11458-007-0037-1
In this paper, we call 3-Nε-benzyloxycarbonyl-L-lysyl-morpholine-2,5-dione Compound A . The starting material used abroad is expensive and the yield is low (16% 28%); furthermore, to our best knowledge, no characterization of Compound A is available in the open literature. We now use low-cost L-lysine as starting material, succeed in raising the yield of Compound A to about 66%, and characterize it. In the synthesis of Compound A, the reactive processes used by us included the protection of amino group of lysine, acetylation, and intramolecular cyclizative condensation reaction. Benzoxycarbonyl chloride was selected as amino group protection agent, and the yield was elevated by replacing sodium bicarbonate with triethyl amide as the acid s neutralizer. The resulting material or Compound A was cyclizative; its structure and properties were characterized by infrared (IR), Differential Scanning Calorimetry (DSC), Nuclear Magnetic Resonance (NMR) and elemental analysis. The results of characterization show that: (1) Compound A has a chiral carbon next to the carbonyl group, so the formation of the ring structure is not stereospecific; (2) the melting point is about 254.5?C. The homopolymer and copolymers of Compound A with lactide or caprolactone have reaction-active groups and excellent biocompatibility and biodegradability; so they can be used in tissue engineering and as controlled-drug-release carriers.
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Volumetric properties of glucose in aqueous HCl solutions at temperatures from 278.15 to 318.15 K
ZHUO Kelei, XUAN Xiaopeng, ZHANG Hucheng, WANG Jianji, ZHANG Qiufen
Front. Chem. China. 2007, 2 (2): 193-198.
https://doi.org/10.1007/s11458-007-0039-z
Densities have been measured for Glucose+HCl+Water at 10-degree intervals from 278.15 to 318.15 K. The apparent molar volumes (Vε,G) and standard partial molar volumes (Vε,G0 ) for Glucose in aqueous solution of 0.2, 0.4, 0.7, 1.1, 1.6, 2.1 mol° kg-1 HCl have been calculated as well as volumetric interaction parameters (VEG) for Glucose-HCl in water and standard partial molar expansion coefficients (aVε,G0/aT)p. Results show that (1) the apparent molar volume for Glucose in aqueous HCl solutions increases lineally with increasing molality of Glucose and HCl; (2) Vε,G0 for Glucose in aqueous HCl solutions increases lineally with increasing molality of HCl; (3) the volumetric interaction parameters for Glucose-HCl pair in water are small positive and vary slightly with temperature; (4) the relation between Vε,G0 and temperature exists as Vε,G0 = ?0+?1(T-273.15 K)2/3; (5) values of (aVε,G0/aT)p are positive and increase as temperatures rise, and at given temperatures decrease slightly with increasing molalities of HCl, indicating that the hydration of glucose decreases with increasing temperature and molality of HCl. These phenomena are interpreted successfully by the structure interaction model.
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A study of using luminophore-doped silica nanoparticles as fluorescent probe in protein microarray assay
LIU Haibo, CHEN Chengxiang, TAN Fang, ZHUANG Zhixia, WANG Xiaoru, YANG Huanghao, YAN Qingpi
Front. Chem. China. 2007, 2 (2): 199-203.
https://doi.org/10.1007/s11458-007-0040-6
A convenient method for the synthesis of tris-(2,2´-bipyridyl) dichlororuthenium(II) hexahydrate-doped amino-modified double-layer silica nanoparticles is presented in this paper. The synthesized nanoparticles are uniform and photostable, and can be well dispersed in a water solution. Proteins could be directly immobilized onto these nanoparticles by a simple coupling process without losing their biological activities. These nanoparticles were further used as fluorescent probes in protein microarray assay for the quantitative detection of protein. The results obtained by these nanoparticles, with the detection limit of as low as 3.5 μg/mL, were much better than those involving the use of conven tional FITC probe.
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Synthesis of high surface area nanometer magnesia by solid-state chemical reaction
GUAN Hongbo, WANG Pei, ZHAO Biying, ZHU Yuexiang, XIE Youchang
Front. Chem. China. 2007, 2 (2): 204-208.
https://doi.org/10.1007/s11458-007-0041-5
Nanometer MgO samples with high surface area, small crystal size and mesoporous texture were synthesized by thermal decomposition of MgC2O4·2H2O prepared from solid-state chemical reaction between H2C2O4·2H2O and Mg (CH3COO)2·H2O. Steam produced during the decomposition process accelerated the sintering of MgO, and MgO with surface area as high as 412 m2·g-1 was obtained through calcining its precursor in flowing dry nitrogen at 520°C for 4 h. The samples were characterized by X-ray diffraction, N2 adsorption, transmission electron microscopy, thermogravimetry, and differential thermal analysis. The as-prepared MgO was composed of nanocrystals with a size of about 4-5 nm and formed a wormhole-like porous structure. The MgO also had good thermal stability, and its surface areas remained at 357 and 153 m2·g-1 after calcination at 600 and 800°C for 2 h, respectively. Compared with the MgO sample prepared by the precipitation method, MgO prepared by solid-state chemical reaction has uniform pore size distribution, surface area, and crystal size. The solid-state chemical method has the advantages of low cost, low pollution, and high yield, therefore it appears to be a promising method in the industrial manufacture of nanometer MgO.
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Comparison of antibacterial ability of copper and stainless steel
GENG Ping, ZHANG Wen, TANG Hui, ZHANG Xinai, JIN Litong, FENG Zhen, WU Zirong
Front. Chem. China. 2007, 2 (2): 209-212.
https://doi.org/10.1007/s11458-007-0042-4
In this paper, the electro-analysis and spectrophotometric analysis methods were used to study the antibacterial ability of copper and stainless steel materials. When Escherichia coli (E. coli) and photo-bacteria were used as samples, the antibacterial effect of stainless steel was very weak, while the percentage of bacteria dying from exposure to metallic copper for 30 min was over 90%. The antibacterial ability of copper has a potential application in the field of disinfection, food packaging and piping of drinking water.
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Synthesis, crystal structure and catalytic activity of a Waugh type polyoxometalate H12[MnMo9O32(KO)6]
WU Dan, XU Meixian, LIN Shen
Front. Chem. China. 2007, 2 (2): 213-217.
https://doi.org/10.1007/s11458-007-0043-3
A Waugh type polyoxometalate H12[Mn-Mo9O32(KO)6] has been synthesized and characterized by single crystal X-ray diffraction, IR, XRD and TG. The compound was crystallized in the trigonal system, space group R3 with a = 15.5380(6) nm, b = 15.5380(6) nm, c = 12.3777(5) nm, α = 90°, β = 90°, γ = 120°, V = 2587.98(18) nm3, Z = 3, R1 = 0.0134, ωR2 = 0.0308. The catalytic activity of the title compound for the dehydration of cyclohexanol was determined. The conversion of C6H11OH reached 69.56% and the selectivity of C6H10 was 96% when the amount of catalyst, temperature range and reaction time were 6.59%, 170°C?180°C, 30 min, respectively.
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An efficient method for the synthesis of 9-β-D-2′-deoxyribofuranosyl-6-methylpurine
LI Shuxin, ZHAO Yanjin, GUO Jinhua, WANG Zhiqing, JIANG Falong
Front. Chem. China. 2007, 2 (2): 218-221.
https://doi.org/10.1007/s11458-007-0044-2
A new method for the preparation of 9-β-D-2´-deoxyribofuranosyl-6-methylpurine from inosine (1) is described. Inosine was converted to 6-chloropurinenucleoside (4) via acetylation, chlorination, and deacetylation. Compound 4 was transformed to the key intermediate 6-methylpurinenucleoside (7) via protection of the 2´,3´,5´-hydroxy groups of 4 with 3,4-dihydropyran to give compound 5, then methylation at the 6-position of 5 with dimethyl copper lithium gave compound 6; depyranylation of 6 led to the subsequent selective protection of the 3´,5´-hydroxy groups of 7 with O[Si(I-Pr)2Cl]2 followed by reaction with phenyl chlorothionoformate to give compound 9. Compound 9 was then converted to the target compound 11 via 2´-deoxidation and 3´, 5´-desilylation. The structures of these products were identified by Mass Spectrum (MS), 1H-NMR (Nuclear Magnetic Resonance) spectra and elemental analysis.
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