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401.
Nonpolar protic reaction media such as t-amyl alcohol allow the aliphatic, nucleophilic fluorination reaction of primary haloalkane systems to fluoroalkanes, using tetrabutylammonium fluoride (TBAF), to proceed chemo-selectively at a reasonable reaction rate under mild conditions to afford the fluoro-product in high yield. As an example, the nucleophilic fluorination of 2-(3-iodopropoxy)naphthalene (1a) as the primary haloalkane model compound, with TBAF in acetonitrile as a polar aprotic solvent, CsF in t-amyl alcohol as a nonpolar protic solvent, and TBAF in t-amyl alcohol for 1 h provided 2-(3-fluoropropoxy)naphthalene (2a) in 38, 5, and 76% yields, respectively. 相似文献
402.
403.
H. N. Lee S. H. Kang S. D. Yang S. C. Sohn 《Journal of Radioanalytical and Nuclear Chemistry》2010,284(3):513-517
Phosphorous containing radioisotope waste was separated and determined by liquid–liquid extraction method through liquid scintillation
counter (LSC). In this process, ammonium phosphate was converted to phosphomolybdate (PMo) by the reaction of ammonium molybdate
(Mo) in HCl solution (0.02 M) and maximum UV/VIS absorbance (λmax) 218 nm was observed. The PMo solution was extracted with TOA (Tri-n-Octylamine)/xylene mixture and λmax 290 nm was found for this organic layer. Absorbance of aqueous and organic layer was linear through concentration. The impurities
such as Co, Cr, Gd, etc. remain in aqueous layer by treating with Mo which was determined by ICP-AES and AAS. The quenching
correction curve for 32P was calculated using LSC results. No counting change was observed as the volume of quenchers increased. The recovery was
98% and 81% for the extraction and separation process from the test using H332PO4 as standard tracer. 相似文献
404.
Sung-Ik Sohn 《Communications in Nonlinear Science & Numerical Simulation》2012,17(11):4017-4022
We examine the multiple harmonic model for the single-mode Rayleigh–Taylor instability, and present a new class of the asymptotic solution for the bubble evolution. Previously reported solutions for the bubble curvature and velocity from the model were quantitatively different from other theoretical models and numerical results, for small density jumps. The discrepancy between the theoretical models is resolved by our new approach to the model. Our solution agrees with the Layzer–Goncharov model, and gives the independence of the bubble curvature on the density ratio. 相似文献
405.
The surfactant effect on the lower critical solution temperature (LCST) of thermosensitive poly(organophosphazenes) with
methoxy-poly(ethylene glycol) and amino acid esters as side groups was examined in terms of molecular interactions between
the polyphosphazenes and surfactants including various anionic, cationic, and nonionic surfactants in aqueous solution. Most
of the anionic and cationic surfactants increased the LCST of the polymers: the LCST increased more sharply with increasing
length and hydrophobicity of the hydrophobic part of the surfactant molecule. The ΔLCSTs (T
0.03M − T
0M), the change in the LCST by addition of 0 and 0.03 M sodium dodecyl sulfate (SDS), were found to be 7.0 and 14.5 °C for the
polymers bearing ethyl esters of glycine and aspartic acid, respectively. The LCST increase of poly(organophosphazene) having
a more hydrophobic aspartic acid ethyl ester was 2 times larger compared with that of the polymer having glycine ethyl ester
as a side group. The binding behavior of SDS to the polymer bearing glycine ethyl ester as a hydrophobic group was explained
from the results of titration of the polymer solutions containing SDS with tetrapropylammonium bromide. Graphic models for
the molecular interactions of polymer/surfactant and polymer/surfactant/salt in aqueous solutions were proposed.
Received: 17 February 2000/Accepted: 25 April 2000 相似文献
406.
Rita Song Kwan Mook Kim Youn Soo Sohn 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(10):e447-e447
The title compound, catena‐poly[[[triaqua‐2κ3O‐(2,2‐dimethyl‐1,3‐propanediamine)‐1κ2N,N′‐μ‐isonicotinato‐1:2κ2N:O‐copper(II)platinum(II)]‐μ‐isonicotinato‐2:1′κ2O:N] dinitrate], {[CuPt(C6H4NO2)2(C5H14N2)(H2O)3](NO3)2}n, obtained from equimolar (dmpda)PtII(isonic)2 (where dmpda is 2,2‐dimethyl‐1,3‐propanediamine and isonic is isonicotinate) and copper(II) nitrate, has been found to be a one‐dimensional coordination polymer of the zigzag‐type. 相似文献
407.
Jung-Sun Sohn Byung-Wook Jo Michael Hess Kirsten Schwark Stephanie Dehne Manfred Zähres 《Macromolecular Symposia》2005,225(1):31-42
The hydrophobic anti-cancer drug paclitaxel was modified with the hydrophilic poly(ethylene oxide) to a water-soluble predrug. The modification of the polymer chain results in a different solution behaviour of the macromolecules compared with the unmodified polymer. The phase diagram of the (quasi)binary system predrug-water was investigated, and molecular simulations of the predrug were executed in vacuum and in the presence of water. The results are important for further engineering on active drug systems. 相似文献
408.
M. Hess B.-W. Jo B. Wermeckes S. Dehne J.-S. Sohn S. Wunderlich M. Zähres 《Macromolecular Symposia》2005,231(1):28-46
A summary of the most recent investigations of conformation and solution properties of a polymer conjugate of the anti-cancer drug paclitaxel is given. First results of spectroscopic studies of interaction with model proteins in the solid state and in solution are discussed. 相似文献
409.
Mary F. Wang Alena N. Joignant Alexandria L. Sohn Kenneth P. Garrard David C. Muddiman 《Journal of mass spectrometry : JMS》2023,58(3):e4911
The field of mass spectrometry imaging (MSI) is constantly evolving to analyze a diverse array of biological systems. A common goal is the need to resolve cellular and subcellular heterogeneity with high spatial resolution. As the field continues to progress towards high spatial resolution, other parameters must be considered when developing a practical method. Here, we discuss the impacts of high spatial resolution on the time of acquisition and the associated implications they have on an MSI analysis (e.g., area of the region of interest). This work presents a brief tutorial serving to evaluate high spatial resolution MSI relative to time of acquisition and data file size. 相似文献