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951.
Dr. Johannes Ammer Dr. Christoph Nolte Prof. Dr. Konstantin Karaghiosoff Sebastian Thallmair Dr. Peter Mayer Prof. Dr. Regina de Vivie‐Riedle Prof. Dr. Herbert Mayr 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(43):14612-14630
The 1H NMR chemical shifts of the C(α)? H protons of arylmethyl triphenylphosphonium ions in CD2Cl2 solution strongly depend on the counteranions X?. The values for the benzhydryl derivatives Ph2CH? PPh3+ X?, for example, range from δH=8.25 (X?=Cl?) over 6.23 (X?=BF4?) to 5.72 ppm (X?=BPh4?). Similar, albeit weaker, counterion‐induced shifts are observed for the ortho‐protons of all aryl groups. Concentration‐dependent NMR studies show that the large shifts result from the deshielding of the protons by the anions, which decreases in the order Cl? > Br? ? BF4? > SbF6?. For the less bulky derivatives PhCH2? PPh3+ X?, we also find C? H???Ph interactions between C(α)? H and a phenyl group of the BPh4? anion, which result in upfield NMR chemical shifts of the C(α)? H protons. These interactions could also be observed in crystals of (p‐CF3‐C6H4)CH2? PPh3+ BPh4?. However, the dominant effects causing the counterion‐induced shifts in the NMR spectra are the C? H???X? hydrogen bonds between the phosphonium ion and anions, in particular Cl? or Br?. This observation contradicts earlier interpretations which assigned these shifts predominantly to the ring current of the BPh4? anions. The concentration dependence of the 1H NMR chemical shifts allowed us to determine the dissociation constants of the phosphonium salts in CD2Cl2 solution. The cation–anion interactions increase with the acidity of the C(α)? H protons and the basicity of the anion. The existence of C? H???X? hydrogen bonds between the cations and anions is confirmed by quantum chemical calculations of the ion pair structures, as well as by X‐ray analyses of the crystals. The IR spectra of the Cl? and Br? salts in CD2Cl2 solution show strong red‐shifts of the C? H stretch bands. The C? H stretch bands of the tetrafluoroborate salt PhCH2? PPh3+ BF4? in CD2Cl2, however, show a blue‐shift compared to the corresponding BPh4? salt. 相似文献
952.
Abstract The isothermal free-radical copolymerization of styrene and acrylonitrile was examined in the temperature range of 333-373 °K. Initial rate studies of styrene homopolymerization were conducted and agreed favorably with values in the literature. Initial rate studies for acrylonitrile solution polymerization in DMF were also performed. Initiator decomposition rate constants measured in the presence of AN and styrene monomer are reported for AIBN, BP, and DTBP. Rate functions for the full spectrum of comonomer compositions initiated by AIBN and benzoyl peroxide are reported. Several copolymerization kinetic models were tested and found to be inadequate. Conversion histories were found to be consistent with observed initial rates and follow a simple pseudohomopolymerization kinetic model. Autoacceleration was observed and found to increase in severity with increased AN feed compositions and decreased reaction temperatures. 相似文献
953.
Dr. Sebastian Seiffert 《Angewandte Chemie (International ed. in English)》2013,52(44):11462-11468
Microgel capsules are micrometer‐sized particles that consist of a cross‐linked and swollen polymer network complexed with additives. These capsules can be actuated by external stimulation if they are formed from sensitive or supramolecular polymer networks. To make this truly useful, it is crucial to control the microgel size, shape, and loading; this can be achieved by droplet‐based microfluidic templating. 相似文献
954.
955.
Abstract Hydrogels in solutions can reversibly swell and collapse with small changes in the process conditions. In this paper we focus on using this characteristic as a purification device. The gels prove to be effective and gentle substitutes for ultrafiltration membranes for the purification of sensitive products such as biomaterials. 相似文献
956.
Sebastian Dochow Claudia Beleites Thomas Henkel Günter Mayer Jens Albert Joachim Clement Christoph Krafft Jürgen Popp 《Analytical and bioanalytical chemistry》2013,405(8):2743-2746
Three important technical innovations are reported here towards Raman-activated cell sorting. Firstly, a microfluidic chip made of quartz is introduced which integrates injection of single cells, trapping by laser fibres and sorting of cells. Secondly, a chip holder was designed to provide simple, accurate and stable adjustment of chips, microfluidic connections and the trapping laser fibres. The new setup enables to the collection of Raman spectra of single cells at 785 nm excitation with 10 s exposure time. Lastly, a new type of modelling the various background contributions is described, improving Raman-based cell identification by the classification algorithm linear discriminant analysis. Mean sensitivity and specificity determined by iterated 10-fold cross validation were 96 and 99 %, respectively, for the distinction of leucocytes extracted from blood, breast cancer cells BT-20 and MCF-7, and leukaemia cells OCI-AML3. 相似文献
957.
New polynitro compounds containing a carbonyl biscarbamate moiety derived from the precursor carbonyldiisocyanate were synthesized. In addition, 2, 2‐dinitropropane‐1, 3‐diyl bis(2, 2,2‐trinitroethylcarbamate) and 2, 2‐dinitropropane‐1, 3‐diyl bis(2, 2,2‐trinitroethyl) dicarbonate, were synthesized using 2, 2‐dinitropropane‐1, 3‐diol as starting material. The compounds were characterized by using the analytical methods, single‐crystal X‐ray diffraction, vibrational spectroscopy (IR and Raman), multinuclear NMR spectroscopy, elemental analysis, and mass spectrometry. The thermal behavior was investigated with DSC measurements. The suitability of the compounds as potential oxidizers in energetic formulations was determined. The heats of formation of the compounds were calculated with GAUSSIAN 09. The detonation parameters such as the detonation pressure, velocity, energy, and temperature were computed using the EXPLO5 code. For a secure handling of the materials, the sensitivity towards impact, friction, and electrical discharge was tested using the BAM drop hammer, BAM friction tester as well as a small‐scale electrical discharge device, respectively. 相似文献
958.
Sebastian Haupt René Schnorr Maria Poetsch Alexander Mansel Marcel Handke Berthold Kersting 《Journal of Radioanalytical and Nuclear Chemistry》2014,300(2):779-786
The Sr2+ extraction properties of some 25,27-bis(carbonylmethoxy)calix[4]arenes, in which ester (–CH2CO2Et), keto (–CH2COCH3) and acid functionalities (–CH2CO2H) have been attached to the lower rim, are reported. Strontium ion extraction experiments were performed in a chloroform/water system, and the extraction performance analyzed by radiotracing using the short-lived radio nuclide 85Sr. Effects of pH value, ligand to metal ratio, temperature, extraction time and strontium species on the extraction behavior were examined. It was observed that the 25,27-bis(carboxymethoxy)calix[4]arene derivatives are potent extracting agents towards the strontium ion, showing remarkable extraction performance in competition with a series of organic and inorganic impurities and in a synthetic groundwater. The crystal structure of 25,27-bis(acetonyloxy)calix[4]arene is also reported. 相似文献
959.
In this article an efficient numerical method to solve multiobjective optimization problems for fluid flow governed by the Navier Stokes equations is presented. In order to decrease the computational effort, a reduced order model is introduced using Proper Orthogonal Decomposition and a corresponding Galerkin Projection. A global, derivative free multiobjective optimization algorithm is applied to compute the Pareto set (i.e. the set of optimal compromises) for the concurrent objectives minimization of flow field fluctuations and control cost. The method is illustrated for a 2D flow around a cylinder at Re = 100. (© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
960.
Mateusz Dako Anna Doga Magdalena Siedzielnik Karol Biernacki Olga Ciupak Janusz Rachon Sebastian Demkowicz 《Molecules (Basel, Switzerland)》2021,26(13)
Herein, we present the synthesis and crystal structures determination of five 4-(1-phenyl-1H-1,2,3-triazol-4-yl)phenol derivatives containing halogen atoms, 6a–e, which may be used as an excellent mimic of steroids in the drug development process. Good quality crystals obtained for all of the synthesized compounds allowed the analysis of their molecular structures. Subsequently, the determined crystal structures were used to calculate the Hirshfeld surfaces for each of the synthesized compounds. Furthermore, results of our docking studies indicated that synthesized derivatives are able to bind effectively to the active sites of selected enzymes and receptors involved in the hormone biosynthesis and signaling pathways, analogously to the native steroids. 相似文献