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991.
Roli Saxena L. D. Kandpal G. N. Mathur 《Journal of polymer science. Part A, Polymer chemistry》2002,40(22):3959-3966
Poly(benzobisthiazole)s containing tetrafluorophenyl and bromophenyl moieties were synthesized via the polycondensation of 2,5‐diamino‐1,4‐benzenedithiol dihydrochloride with tetrafluorophthalic acid and 4‐bromoisophthalic acid under a nitrogen atmosphere. The polymers were characterized by X‐ray diffraction, spectroscopy (infrared and solid‐state 13C NMR), and thermal analysis, including differential scanning calorimetry and thermogravimetric analysis. The thermogravimetric analysis showed that the thermal stability of the polymers was 490–515 °C under a nitrogen atmosphere. The synthesized polymers showed good solubility in organic solvents. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3959–3966, 2002 相似文献
992.
N. Nassif A. Coiffier T. Coradin C. Roux J. Livage O. Bouvet 《Journal of Sol-Gel Science and Technology》2003,26(1-3):1141-1144
Whole E. coli bacteria have been trapped within silica gels obtained via the acidification of sodium silicate and silica nanoparticles solutions. Their -galactosidase enzymatic activity increases with time, suggesting that their membrane is partially lysed during the encapsulation process. Such a lysis can be greatly reduced when encapsulation is performed in the presence of gelatin. The biocatalytic activity of trapped bacteria remains almost constant for more than a week. Moreover bacteria trapped in such gels remain able to incorporate glucose, showing that their viability has been preserved. 相似文献
993.
994.
Miho Katoh 《Tetrahedron letters》2005,46(31):5161-5163
A stereoselective synthetic route to Nuphar quinolizidine alkaloid, (−)-deoxynupharidine, was established by employing reductive carbon-nitrogen bond cleavage, followed by simultaneous recyclization of a proline derivative with samarium diiodide, and an intramolecular ring-closing metathesis, as the key steps. 相似文献
995.
1-Alkyl imidazoles react smoothly with dialkyl acetylenedicarboxylates in the presence of pyridine carboxaldehydes to diastereoselectively produce 1,8a-dihydro-7H-imidazo[2,1-b][1,3]oxazine derivatives in excellent yields. 相似文献
996.
Silke Schmetzer Paulette Greenidge Karl-Artur Kovar Meike Schulze-Alexandru Gerd Folkers 《Journal of computer-aided molecular design》1997,11(3):278-292
A cannabinoid pseudoreceptor model for the CB1-receptor has been constructed for 31 cannabinoids using the molecular modelling software YAK. Additionally, two CoMFA studies were performed on these ligands, the first of which was conducted prior to the building of the pseudoreceptor. Its pharmacophore is identical with the initial superposition of ligands used for pseudoreceptor construction. In contrast, the ligand alignment for the second CoMFA study was taken directly from the final cannabinoid pseudoreceptor model. This altered alignment gives markedly improved cross-validated r2 values as compared to those obtained from the original alignment with
values of 0.79 and 0.63, respectively, for five components. However, the pharmacophore alignment has the better predictive ability. Both the CoMFA and pseudoreceptor methods predict the free energy of binding of test ligands well. 相似文献
997.
If, in volumetric analysis, the solution, as well as the reagent, is measured by means of a burette (replacing the usual pipette), we are able, after reaching the first end-point, to add a small quantity of either solution, substance or reagent, to titrate for a second end-point and to repeat these operations as many times as are necessary to obtain an average value with the desired accuracy, which 'can be very high. The economy, both in tbc amount of solution required and time, is considerable. The procedure is very useful in theoretical .studies on controversial volumetric reactions and in calibrating burettes. 相似文献
998.
Characterization of sixty alkenes in a cat-cracked gasoline naphtha by gas chromatography 总被引:3,自引:0,他引:3
Summary The alkene-rich petrol fraction from refinery fluid catalytic cracking (FCC) has been characterized by GC and GC-MS. Quantitative proportions and retention data of 52 acyclic and 11 cyclic C5–C7 alkenes are given. Relative retentions are reported for methylsilicone and aluminium oxide stationary phases as methylene units (MU). Applications of mass spectra, single-ion GC-MS monitoring and retention data for identifications are demonstrated. 相似文献
999.
The Crystal Structure of Me3SiI · β-Picoline and Me3SiI · γ-Picoline A Comparison between the Lewis-Bases Pyridine, β-Picoline, and γ-Picoline The reaction of Iodinetrimethylsilane with β- und γ-Picoline (Pic) leads to solid 1 : 1 compounds Me3SiI · β-Picoline 1 , Me3SiI · γ-Picoline 2. The reaction was performed at room temperature. Yellow single crystals were obtained by sublimation. Single crystal X-ray investigations confirm that both compounds are ionic [Me3SiPic]+I?. The comparison of β-Picoline with γ-Picoline and Pyridine (Py) demonstrates that the presence of a methyl group and also its position has no significant influence on the Si? N bond length in compound 1, 2 and on the adduct Me3SiI · Py. 相似文献
1000.
邻硝基苯基荧光酮化学发光性能和机理研究 总被引:7,自引:1,他引:7
研究了在碱性介质中金属离子催化邻硝基苯基荧光酮(o-NPF)-H2O2体系的化学发光行为。结果表明,在研究的20多种金属离子中,只有Co2+离子对o-NPF-H2O2体系有较强的催化发光作用,Co2+的浓度与发光强度在2.5×10-9~3.0×10-6g/mL范围内呈良好的线性关系。通过对化学发光光谱、荧光光谱的研究以及用Huckel分子轨道法(HMO)计算了o-NPF的π电子分布和键级,提出了o-NPF可能的化学发光机理. 相似文献