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121.
Katarina Leko Marko Hanževački Dr. Zlatko Brkljača Dr. Katarina Pičuljan Dr. Rosana Ribić Dr. Josip Požar 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(23):5208-5219
The effects of solvent and temperature on the complexation of adamantyl mannoside with β-cyclodextrin and 6-O-monotosyl-6-deoxy-β-cyclodextrin were explored experimentally and by means of molecular dynamics simulations. Efficient binding was observed only in hydrogen-bonded solvents, which indicated solvophobically driven complexation. The stability of the inclusion complex was considerably higher in aqueous media. A pronounced temperature dependence of ΔrH○ and ΔrS○, resulting in perfect enthalpy–entropy compensation, was observed in water. The complexation thermodynamics was in line with classical rationale for the hydrophobic effect at lower temperatures and the nonclassical explanation at higher temperatures. This finding linked cyclodextrin complexation thermodynamics with insights regarding the effect of temperature on the hydration water structure. The complexation enthalpies and entropies were weakly dependent on temperature in organic media. The signs of ΔrH○ and ΔrS○ were in accordance with the nonclassical hydrophobic (solvophobic) effect. The structures of the optimized product corresponded to those deduced spectroscopically, and the calculated and experimentally obtained values of ΔrG○ were in very good agreement. This investigation clearly demonstrated that solvophobically driven formation of cyclodextrin complexes could be anticipated in structured solvents in general. However, unlike in water, adamantane and the host cavity behaved solely as structure breakers in the organic media explored so far. 相似文献
122.
123.
124.
A. Dobrak B. Verrecht H. Van den Dungen A. Buekenhoudt I.F.J. Vankelecom B. Van der Bruggen 《Journal of membrane science》2010
This paper describes solvent flux and rejection behavior of different hydrophilic TiO2 membranes and a hydrophobic ZrO2 membrane. Solvents and solutes used range from polar to non-polar. Additionally, the temperature effect on permeability and rejection of solutes through these membranes was examined. 相似文献
125.
Yoshitaka Nakano Yoshihiro Irokawa Yasunobu Sumida Shuichi Yagi Hiroji Kawai 《固体物理学:研究快报》2010,4(12):374-376
We have investigated electronic deep levels in two AlGaN/GaN hetero‐structures with different current collapses grown at 1150 and 1100 °C by a photo‐capacitance spectroscopy technique, using Schottky barrier diodes. Three specific deep levels located at ~2.07, ~2.80, and ~3.23 eV below the conduction band were found to be significantly enhanced for severe current collapse, being in reasonable agreement with photoluminescence and capacitance–voltage characteristics. These levels probably originate in Ga vacancies and residual C impurities and are probably responsible for the current collapse phenomena of the AlGaN/GaN hetero‐structures. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
126.
Summary A high-performance liquid chromatographic method for the simultaneous determination of urinary organic acids and creatinine for following the metabolism of aromatic solvents is reported. After extraction of acidified, filtered urine with diethylether followed by evaporation, the dried residue is dissolved in mobile phase. Hydroxybenzoic acid is used as internal standard. A column of Nucleosil C18 is used with a precolumn of the same material. The mobile phase is acetonitrilephosphate buffer, pH 3.3 (1783). For determination of creatinine the sample is simply diluted 10-fold and the eluate monitored at 215 nm (UV). This technique gives highly reproducible results and is simple, reliable and useful for biological monitoring. 相似文献
127.
On the structure formation of hydrophobed particles in the boundary layer of water and octane phases
Two-dimensional aggregation of the surface modified glass beads was carried out in the boundary layer of water and octane phases. The effect of particles' hydrophobicity was investigated on the structure of forming aggregates and the growth process. The structure of the aggregates and their growth were characterized by a density function which demonstrates the change of mean particle density as a function of aggregate size. The growth yielded fractal or nonfractal structures in the investigated systems. The fractal structure of the aggregates was observed to be dependent on restructuring processes controlled by the surface properties of the beads.The experimental results are compared with earlier findings for aggregation of hydrophobic beads in the boundary layer of water and air phases.On leave from Loránd Eötvös University, Budapest, Hungary 相似文献
128.
S. Sawamura M. Tsuchiya T. Ishigami Y. Taniguchi K. Suzuki 《Journal of solution chemistry》1993,22(8):727-732
Solubility of naphthalene in water was measured at 25°C and pressures up to 200 MPa. The solubility decreased with increasing pressure. From the pressure coefficient of the solubility, the volume change V accompanying the dissolution was estimated as 13.8±0.4 cm
3
-mol
–1
. Further we estimated the volume change V
CH
accompanying hydrophobic hydration as –0.1±0.6 cm
3
-mol
–1
using the V value, the molar volume of crystalline naphthalene, and the partial molar volume of naphthalene in n-heptane. This V
CH
is much larger (i.e., less negative) than that for hydrophobic hydration of alkyl-chain compounds and suggests that the hydration structure of naphthalene differs from that of alkyl-chain compounds. 相似文献
129.
Dafna Knani Arie L. Gutman David H. Kohn 《Journal of polymer science. Part A, Polymer chemistry》1993,31(5):1221-1232
With the object to synthesize polyesters by enzymatic catalysis in organic media, two directions have been investigated: (1) the condensation polymerization of linear ω-hydroxyesters and (2) the ring-opening polymerization of lactones. The commercially-available crude porcine pancreatic lipase (PPL), suspended in organic solvents, was the preferred enzyme for the reactions. In order to determine the optimal conditions for the condensation polymerization, the bifunctional methyl 6-hydroxyhexanoate was used as a model compound to study the influence of the following parameters: type of the enzymecatalyst, kind of solvent, concentration, temperature, duration, size of the reaction mixture, and stirring. Film-forming polyesters with a degree of polymerization (DP) up to about 100 were obtained from linear aliphatic hydroxyesters in n-hexane at reflux temperature (69°C). Yet concurrently with the intermolecular condensation polymerization, macrolactones were also formed by intramolecular reaction. Two aromatic hydroxyesters did not react under these conditions. For the ring-opening polymerization of lactones the reaction of ?-caprolactone with methanol as the preferred nucleophile, was studied. Polyesters with a DP of up to 35 were obtained in n-hexane at temperatures between 25 and 40°C. The degrees of polymerization of the polyesters were determined by comparative analyses of the end groups in the 1H-NMR spectra and by determination of molecular weights either by vapor phase osmometry, gel permeation chromatography, or intrinsic viscosity. © 1993 John Wiley & Sons, Inc. 相似文献
130.
Single-drop microextraction (SDME) has been recognized as one of the simple miniaturized sample preparation tools for the isolation and preconcentration of several analytes from a complex sample matrix. In this review, we explored the applications of SDME coupled with various analytical techniques (spectroscopy, chromatography, and mass spectrometry) for the analysis of organic molecules, inorganic ions, and biomolecules from various sample matrices including food, environmental, clinical, pharmaceutical, and industrial samples. Also, it summarizes the use of nanoparticles in SDME combined with various analytical tools for the rapid analysis of several trace-level target analytes. An overview of ionic liquids, deep eutectic solvents, and SUPRAS, which improved the selectivity and sensitivity of various analytical techniques toward several analytes, as promising extracting solvent systems in SDME is also included. Finally, discussed the impressive analytical features and future perspectives of SDME in this review article. 相似文献