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101.
We have investigated the effect of salt concentration and temperature on the average aggregation number and micro-polarity of the interior of micelles of sodium dodecyl sulfate (SDS). sodium tetradecyl sulfate (STDS) and lithium dodecyl sulfate (LiDS). The transient fluorescence decay of micelle-solubilized pyrene has been measured and analyzed. An exponent weighted average aggregation number <n>e was obtained by this technique. For SDS and STDS in NaCl solution, <n>e increases as the temperature is lowered or salt concentration is increased <n>e increased from ~ 50 to ~ 250 over [NaCl] = 0 to 0.8 M. Due to the strong counterion binding of lithium in the micellar solution, the LiDS micelle is much, smaller and does not increase appreciabily even at [LiCl] =0.8 M. From the fluorescence spectrum fine structure of pyrene and the fluorescence decay of the monomer and excimer, we can understand the local polarity and the water penetration to the interior of the micelle upon addition of salts and with changing temperature. The interior of the micelle becomes more nonpolar as the salt concentration is increased and the temperature is lowered. A complete kinetic analysis of the time–dependence of the fluorescence is given. The kinetic analysis is in agreement with the results reached by fluorescence spectral analysis. 相似文献
102.
[reaction: see text] Copper(I)-mediated C-N bond formation has been employed to prepare both N-acyl vinylogous carbamic acids and ureas. The novel N-acyl vinylogous carbamic acid antibiotic, CJ-15,801, was synthesized using this methodology. 相似文献
103.
Xiao WL Zhu HJ Shen YH Li RT Li SH Sun HD Zheng YT Wang RR Lu Y Wang C Zheng QT 《Organic letters》2005,7(11):2145-2148
[structure: see text]. Lancifodilactone G (1), a novel, highly oxygenated nortriterpenoid featuring a partial enol structure and a spirocyclic moiety, was isolated from the medicinal plant Schisandra lancifolia. Its structure and stereochemistry were determined from extensive one- and two-dimensional NMR and mass spectral data, coupled with single-crystal X-ray analysis. Compound 1 exerted minimal cytotoxicity against C8166 cells (CC50 > 200 microg/mL) and showed anti-HIV activity with EC50 = 95.47 +/- 14.19 microg/mL and a selectivity index in the range of 1.82-2.46. 相似文献
104.
Qiong Yu Lai Ji Zheng LuXiao Bo Su Xiao Yang Ji 《Journal of solid state chemistry》2002,165(2):312-316
Spinel compound LiNi1−xMnxVO4 (0≤x≤0.4) had been prepared by using the moist chemical method. X-ray diffraction spectra showed that the lattice constant increased with x in the LiNi1−xMnxVO4, XPS spectra indicating that Li1s had a chemical shift towards lesser binding energy, and manganese in LiNi1−xMnxVO4 existing as the mixed valence of Mn2+ and Mn3+. The electrochemical charge and discharge testing at a current density of 0.1 mA/cm2 between the potentials of 4.0 and 3.0 V vs Li/Li+ in 1 mol/dm3 LiPF6/EC+DEC (1:1 by volume) at 25°C showed that LiNi1−xMnxVO4 cell has a better rechargeability, but a lower cell voltage of 4.0 V vs Li/Li+ than that without the doping sample, and the capacity and the cycle efficiency of the Li/LiNi1−xMnxVO4 cells increased with x in the LiNi1−xMnxVO4. 相似文献
105.
介绍了锗在光纤通信中的作用,分析了世界光纤市场的变化及其对锗的市场结构的影响,预测近期国内锗的市场结构不会有大的变化。 相似文献
106.
Kim MS Seo KS Khang G Lee HB 《Langmuir : the ACS journal of surfaces and colloids》2005,21(9):4066-4070
A gradient polyethylene (PE) surface was created through corona treatment, in which the corona power increased along the 5 cm length of the PE. The gradient surface was treated with polyethyleneimine and then biotin. Fluorescein-conjugated streptavidin (SAV) caged within 5-carboxymethoxy-2-nitrobenzyl (CMNB) adsorbed onto the biotinylated gradient PE surface following molecular recognition principles. Photoirradiation decomposed the CMNB cage and allowed the fluorescein-conjugated SAV to fluoresce, the intensity of which increased gradually along the PE surface. 相似文献
107.
Effect of amphiphilic molecules upon the chromatic transitions of polymerized 10,12-pentacosadiynoic acid (PCDA) vesicles in aqueous solutions was reported. The colorimetric response of polymerized PCDA vesicles for 1-pentanol is higher than that for ethanol due to more hydrophobic property of 1-pentanol. The colorimetric response of polymerized PCDA vesicles for sodium dodecyl sulfate (SDS) and Triton X-100 is lower than that for cetyltrimethylammonium bromide (CTAB). The strong ability of CTAB to induce chromatic transition of the vesicles is related to the positively charged headgroups of CTAB, which favors approach of CTAB to the negatively charged carboxylate groups at the vesicle surface. The insertion of alkyl chain of CTAB into the hydrophobic domain perturbs the conformation of the conjugated polymer backbone and induces color change of polydiacetylene vesicles. For a series of alkylamine hydrochloric salts, the longer the alkyl chain, the stronger the ability of alkylamine to induce chromatic transition of polydiacetylene vesicles. 相似文献
108.
It is generally accepted that the compensation effect arises when a linear relation between InA andE is detected for a simple reaction taking place over different catalysts or for different reactions over one catalyst. For a perfect linear relation between InA andE representation of the reaction rate constant in an Arrhenius plot results in a series of straight lines which intersect in a single point. The importance is stressed of defining unambiguously what is meant by the compensation effect, and it is shown how the scatter in the values of InA is translated into Arrhenius plots. 相似文献
109.
Zhang YZ Gao S Sun HL Su G Wang ZM Zhang SW 《Chemical communications (Cambridge, England)》2004,(17):1906-1907
Cyano-bridged corrugated ladder-like chains are connected by mu(1,1)-N(3) (end-on, EO) bridges to form a layered coordination polymer, [Mn(N(3))(CH(3)OH)[Cr(phen)(CN)(4)].CH(3)OH (2), which is the first mixed cyano-azide bridged compound, and shows metamagnetism below 21.8 K, a temperature much higher than that (3.4 K) of the crossed double chain [Cr(phen)(CN)(4)](2) [Mn(H(2)O)(2)].4H(2)O (1) based on the same building block [Cr(phen)(CN)(4)](-). 相似文献
110.
Madhushaw RJ Li CL Su HL Hu CC Lush SF Liu RS 《The Journal of organic chemistry》2003,68(5):1872-1877
In the presence of BF3*Et2O, alkynyltungsten complexes underwent [3 + 2] cycloaddition with tethered epoxides to give bicyclic -lactones efficiently. Only one diastereomeric product was formed despite the presence of three stereogenic centers. A mechanism is proposed that involves formation of a tungsten-vinylidenium species via an SN2 attack of the epoxide carbon by an alkynyltungsten group to give a tungsten-enol ether species via counterattack at the central tungsten-vinylidenium carbon by the OBF3- terminus. Most of the tungsten enol ether species were too unstable for isolation and underwent hydrolysis to give only cis-fused -bicyclic lactones. This cyclization works for both cis- and trans-epoxides and tolerates various functional groups. In the case of trans-phenyl epoxide, the reaction led to an addition product via a 6-endo attack of epoxide by the tungsten fragment. This method provides a simple enantiospecific synthesis of complex bicyclic lactones if a chiral epoxide is used in the cyclization. It is also applicable to the one-pot synthesis of bicyclic unsaturated gamma-lactones if a suitable alkynyltungsten functionality is used. 相似文献