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31.
Anionic water-soluble siloxanes modified with different amounts of alkyl chains have been used as pseudostationary phases in electrokinetic chromatography. Ionic siloxane polymers with attached alkyl chains of C8 and C12 and having different alkyl chain densities have been employed previously to achieve selective and efficient separations with a range of electrophoretic mobilities and methylene selectivities. In this study, the performance of three alkyl-modified siloxanes is examined in different organic-modified buffers and at differing amounts of organic modifier. The organic modifiers used are acetonitrile and methanol. The siloxanes are stable in these organic solvents and show good mobility and good methylene selectivities even at high concentration of organic solvent. Siloxanes have also been used to separate a mixture of 14 polynuclear aromatic hydrocarbons in an acetonitrile-modified buffer. 相似文献
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Haas P Hempstead M Jensen T Kagan H Kass R Behrends S Gentile T Guida JM Guida JA Morrow F Poling R Rosenfeld C Thorndike EH Tipton P Besson D Green J Namjoshi R Sannes F Skubic P Stone R Bortoletto D Chen A Goldberg M Horwitz N Jawahery A Lubrano P Moneti GC Trahern CG van Hecke H Csorna SE Garren L Mestayer MD Panvini RS Word GB Yi X Alam MS Bean A Ferguson T Avery P Bebek C Berkelman K Blucher E Cassel DG Copie T DeSalvo R DeWire JW Ehrlich R Galik RS Gilchriese MG Gittelman B Gray SW 《Physical review letters》1985,55(12):1248-1251
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Frampton MJ Akdas H Cowley AR Rogers JE Slagle JE Fleitz PA Drobizhev M Rebane A Anderson HL 《Organic letters》2005,7(24):5365-5368
[structure: see text] A vinylene-linked porphyrin dimer, with no substituents at the beta-positions, has been synthesized by CuI/CsF promoted Stille coupling. In the crystal structure of this dimer, the C(2)H(2) bridge is twisted by 45 degrees relative to the plane of the porphyrins. The absorption, emission spectra, and electrochemistry reveal substantial porphyrin-porphyrin pi-conjugation. The triplet excited-state absorption spectrum of this dimer makes it suitable for reverse saturable absorption at 710-900 nm. 相似文献
37.
Carter DL Draper MC Peterson RN Shah DO 《Langmuir : the ACS journal of surfaces and colloids》2005,21(22):10106-10111
At the end of the final spin cycle of the laundry process, the residual moisture content (RMC) of fabric is directly related to the dynamic surface tension of the residual water in the fabric. The LaPlace equation for capillary rise predicts that the capillary rise of solutions in a capillary is proportional to the surface tension at the air-liquid interface. If fabric can be considered to be a large ensemble of capillaries due to interfiber spacing, then the RMC of fabrics will be directly related to the surface tension of residual solution in the fabric. The use of a tailored rinse additive has the potential to decrease the surface tension of solution significantly, thus leading to a decrease in the residual water content of the fabric. It is expected that as the surfactant concentration increases the surface tension decreases. Hence, the RMC of fabrics must decrease with increasing surfactant concentration. However, a peak is observed in the RMC of fabrics before the critical micelle concentration (CMC) is reached. Prior to the CMC, it is proposed that a sudden adsorption of surfactant is occurring on the fabric surface leading to a decrease in bulk monomer concentration. The decrease in free monomer concentration should result in an increase in the equilibrium surface tension of the residual solution leading to a concomitant increase in RMC. Because the dynamic surface tension is measured on a short time scale (on the order of milliseconds), there will be less adsorption of monomer onto the newly created air-liquid interface of the bubbles during the measurement process. This decrease in adsorption should lead to a pronounced increase in the dynamic surface tension. This indeed was observed. The RMC correlates very well with the dynamic surface tension of the residual solution. 相似文献
38.
Paul E. Peterson 《Tetrahedron letters》1981,22(14):1295-1298
Electronegativities may be used to rationalize the observation that the equilibrium, CH3(CH2)3I + (CH3)3SiCH2Cl ? CH3(CH2)3Cl + (CH3)3SiCH2I, lies to the right. 相似文献
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The first example of a twenty-four membered mixed p-/s-block macrocycle, cyclo-[(3-Me-1,2-C6H3O2)2SbNa(THF)2]6 1 has been synthesised and structurally characterised from the reaction between 3-Me-1,2-C6H3(OH)(ONa) and (Me2N)2Sb(CH2)3Sb(NMe2)2. 相似文献
40.
Crystal engineering of novel cocrystals of a triazole drug with 1,4-dicarboxylic acids 总被引:4,自引:0,他引:4
Remenar JF Morissette SL Peterson ML Moulton B MacPhee JM Guzmán HR Almarsson O 《Journal of the American Chemical Society》2003,125(28):8456-8457
Cocrystals of the poorly soluble antifungal drug cis-itraconazole (1) with 1,4-dicarboxylic acids have been prepared. The crystal structure of the succinic acid cocrystal with 1 was determined to be a trimer by single-crystal X-ray. The trimer is comprised of two molecules of 1 oriented in antiparallel fashion to form a pocket with a triazole at either end. The extended succinic acid molecule fills the pocket, bridging the triazole groups through hydrogen-bonding interactions rather than interacting with the more basic piperazine nitrogens. The solubility and dissolution rate of some of the cocrystals are approximately the same as those of the amorphous drug in the commercial formulation and are much higher than those for the crystalline free base. The results suggest that cocrystals of drug molecules have the possibility of achieving the higher oral bioavailability common for amorphous forms of water-insoluble drugs while maintaining the long-term chemical and physical stability that crystal forms provide. 相似文献