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991.
Yu. V. Tomilov I. V. Kostyuchenko E. V. Shulishov O. M. Nefedov 《Russian Chemical Bulletin》1997,46(3):511-518
The reaction of diazocyclopropane generatedin situ with acrylonitrile or methyl acrylate to give 1∶1, 1∶2, and 2∶1 cycloadducts was carried out. The products resulting from
1,3-dipolar cycloaddition and subsequent isomeriation,viz., 3-cyano- and 3-methoxycarbonylspiro(2-pyrazoline-5,1′-cyclopropanes), isolated in the first step in ∼70% yield, react in
an alkaline solution with the above acrylates or diazocyclopropane as C(3)-nucleophiles to give the corresponding 3-(2′-cyanoethyl)-,
3-(2′-methoxycarbonylethyl)-, or 3-(cyclopropylazo)-1-pyrazolines. The thermal deazotization of these pyrazolines to spiropentane
derivatives was investigated.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 532–539, March, 1997. 相似文献
992.
An electrochemical method for the simultaneous determinations of HgII concentration and total AsIII and AsV concentration has been developed. The method does not require the additional preliminary step of the chemical reduction of AsV to AsIII, or oxidation of AsIII to AsV before stripping analysis takes place. Also, the method for the simultaneous determination of HgII concentration and AsIII concentration is described. Measurements were performed in 0.1 M HCl using a gold-plated graphite electrode as sensor. Detection limits for both methods are below 0.4 ppb. Relative standard deviation did not exceed 15%. The possible interference by other trace metals was investigated. Analyses of natural water and industrial solutions were made using proposed methods and AAS. The t-test demonstrates that there was no significant difference between the results obtained with these methods. Proposed methods decrease the time of analysis because concentrations of the HgII and arsenic ions were measured simultaneously. Also, the removal of the additional step of chemical reduction of AsV to AsIII or oxidation of AsIII to AsV decreases analysis time, and also reduces the chance of contamination due to the use of additional reagents. 相似文献
993.
Benchmarking of ruthenium initiators for the ROMP of a norbornenedicarboxylic acid ester 总被引:1,自引:0,他引:1
Sandra Demel Wolfgang Schoefberger Christian Slugovc Franz Stelzer 《Journal of molecular catalysis. A, Chemical》2003,200(1-2):11-19
The kinetic study of ring-opening metathesis polymerization (ROMP) of a diester functionalised norbornene derivative, (±)-exo,endo-bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic acid diethyl ester, with a series of ruthenium benzylidene complexes revealed the applicability of these initiators for well defined polymerization reactions. Values for the rate of initiation as well as the rate of propagation of the initiators were determined and correlated to the molecular weight and polydispersity of the isolated polymers. As the only initiator providing an entry to virtually monodisperse polymers the classical “first generation Grubbs-catalyst” was identified, while N-heterocyclic carbene based initiators polymerized with a rate of propagation much higher than the rate of initiation yielding polymers with a broader molecular weight distribution. 相似文献
994.
Xiaoxia WangYongmin Zhang 《Tetrahedron》2003,59(23):4201-4207
N-Acylbenzotriazoles, when treated with samarium diiodide in THF, undergo self-coupling reaction to afford 1,2-diketones in good to excellent yields; while when treated with samarium diiodide in CH3CN, they undergo ring-opening reaction to afford 1-acylamido-2-alkyl (or aryl) benzimidazoles in reasonable to good yields. A plausible mechanism was suggested. 相似文献
995.
在自制的硅基纤维素-三(3,5-二甲基苯基氨基甲酸酯)高效液相色谱手性固定相上(HPLC-CSP),优化了1-(6'-甲氧基萘)乙醇氢酯基化反应产物-萘普生甲酯手性分离的条件,测定了相应的一系列不对称氢酯基化反应产物的对映体过剩值(e.e.值)。结果表明,在CDMPC-CSP手性柱上用HPLC测定此类不对称催化反应的光学产率,评价催化剂体系的手性选择是一种非常理想的方法。 相似文献
996.
997.
A novel hyperbranched polyester acrylate (HPEA) was synthesized based upon ethylenediamine tetraacetic acid as a “core” molecule, 5‐hydroxyisophthalic acid as an AB2 monomer, and 2‐hydroxyethyl acrylate as an endcapping reagent. The obtained oligomer has an unsaturation concentration of 4.10 mmolC?C g?1 measured by nuclear magnetic resonance and a wide molecular weight distribution of 1.64 measured by gel permeation chromatography. The two‐photon absorption (TPA) photopolymerization of HPEA under the exposure of a Ti : sapphire femtosecond laser with a wavelength of 800 nm was investigated through laser exposure dose‐dependant spatial resolutions of its resins. The TPA photopolymerization thresholds at the range 1.6–4.3 × 107 mJ cm?2, and exposure dose windows at the range 3.4–4.3 for three formulations were determined. A spatial resolution of 0.85 μm was obtained through the TPA photopolymerization of the formulation containing 1 wt% photoinitiator and 0.3 wt% photoinhibitor. A diffraction grating and real three‐dimensional coupled gear wheel created by TPA photopolymerization were described to demonstrate the unique capability of HPEA in microfabrications. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
998.
V. A. Dorokhov L. S. Vasil'ev N. Kyu Khoa N. Kong Hao V. S. Bogdanov 《Russian Chemical Bulletin》1997,46(11):1967-1969
A method for the synthesis of 2,2′-bipyridin-4-one from 4-amino-4-(2-pyridyl)-but-3-en-2-onevia its diphenylboron, chelates was proposed.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2071–2073, November, 1997. 相似文献
999.
The stability of hexacyanoferrate(II)-amine(methylamine, ethylenediamine, diethylenetriamine and tetraethylenepentamine) was determined potentiometrically. Species Fe(CN)6(A)H
j
(j–4)
(A=amine) are formed in all the systems investigated, with j=1...n+2 (n=number of aminogroups). Some other complexes Fe(CN)6(A)iHj (with i>1) were also found. The stability of these complexes is fairly high: the full protonated amine species, show for the reaction Fe(CN)6
4- + HnAn+ = Fe(CN)6(A)Hn
(n-4) an equilibrium constant given by logK=0.686+2.10n. Factors affecting the stability are discussed in comparison with similar systems, together with the importance of interferences. 相似文献
1000.
以交联聚乙烯醇为载体的离子交换剂对蛋白质的分离性能 总被引:2,自引:0,他引:2
本文对阴离子交换剂DEA—PVT常压液相离子交换色谱分离蛋白质的性能、分离条件进行了探讨。结果表明其对蛋白质的分离性能良好,容易洗脱。与载体交联聚乙烯醇相比,DEA—PVT对蛋白质的非特异性吸附明显降低。 相似文献