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101.
102.
When 4-hydroxyacetophenone is treated with MSTFA the corresponding bis-trimethylsilylated enol ether (1a) is obtained. The mass spectrum of la is characterized by a [M – 1]+ base peak. Extensive deuteration experiments revealed that the hydrogen is mainly removed from a ring position, but originates also to some extent from the side chain (methylidene group) and even to a very small amount from the hydrogens of the methyl groups of the enolic trimethylsilyl group. A mechanism for this fragmentation behaviour is formulated. 相似文献
103.
Jan P. C. Bootsma Leo A. M. Rupert Ger Challa Franz Müller 《Journal of polymer science. Part A, Polymer chemistry》1984,22(9):2169-2180
The strong influence of medium composition (water/2-propanol mixtures) on the rate of oxidation of 1-substituted dihydronicotinamides by a flavin-containing polyelectrolyte was studied. We found that the coil dimensions of the corresponding copolymer of styrene and vinylbenzyltriethylammoniumchloride without flavin groups dramatically depend on the solvent. Viscometric measurements revealed compact coil conformations in solvents of both high water and high 2-propanol content, but pronounced coil expansion in intermediate mixtures. These changes of polyelectrolyte coil dimensions are related to changes in electrostatic potential of the microreactors. Addition of 2-propanol also results in decrease of substrate enrichments, caused by weakening of nonpolar polymer–substrate interactions, as was demonstrated for 1-carbamoylmethyl-, 1-benzyl-, and 1 decyl-substituted 1,4-dihydronicotinamide substrates. The enormous decrease in rate constant for oxidation of DNAH by 2 upon increasing the 2-propanol content from 10 to 40% (v/v), from k = 3120 to 21 M?1 s?1, can thus be explained as a cooperation of both effects. Evidence for the formation of a charge transfer complex between the polyelectrolyte-bound flavin and the dihydronicotinamide having a long-wavelength absorption is also presented. 相似文献
104.
Karsten Malsch Rupert Rebentisch Petra Swiderek Georg Hohlneicher 《Theoretical chemistry accounts》1998,100(1-4):171-182
Valence and low-lying Rydberg states of acetylene (C2H2) are reexamined in the singlet as well as in the triplet manifold. The major goal of this work is a better understanding
of the valence states that contribute to the low-energy electron-energy-loss spectrum recorded under conditions where transitions
to triplet states are enhanced. An appropriate theoretical treatment of these states has to include the low-lying Rydberg
states because of their energetic proximity to some of the valence states. The CASSCF/CASPT2 method provides a suitable framework
for such a task. For some important states the geometry was optimized at the CASPT2 level to allow a comparison with the results
of other highly accurate methods that have been applied to acetylene in the past.
Received: 11 June 1998 /Accepted: 30 July 1998 / Published online: 19 October 1998 相似文献
105.
Advanced Oxidation Processes (AOPs) for wastewater treatment are gaining more importance since biological treatment plants
are often not sufficient for highly contaminated or toxic wastewaters. In order to find out the most efficient and cheap AOP, investigations were concentrated on methods that can use sunlight. The systems TiO2/UV, Fe2+/H2O2/UV (Photo-Fenton reaction), Fe2+/O2/UV and Fe2+/O3/UV were compared. Since the Photo-Fenton system was the most effective, pilot plant experiments with industrial wastewaters
and sunlight experiments were carried out. Finally a rough cost estimate shows that Photo-Fenton treatment with sunlight is
far cheaper than other available AOPs, namely ozonization. 相似文献
106.
Dr. Klaus Hartmann Dr. Rolf Wim Henrichs Dr. Rupert Lasser 《Monatshefte für Mathematik》1979,88(3):229-238
For a locally compact groupG and a groupB of topological automorphisms containing the inner automorphisms ofG and being relatively compact with respect to Birkhoff topology (that isG[FIA]
B,B
I(G)) the spaceG
B of
-orbits is a commutative hypergroup (=commutative convo inJewett's terminology) in a natural way asJewett has shown. Identifying the space of hypergroup characters ofG
B withE(G, B) (the extreme points ofB-invariant positive definite continuous functionsp withp (e)=1, endowed with the topology of compact convergence) we prove thatE(G, B) is a hypergroup, the hypergroup dual ofG
B. 相似文献
107.
Konradi R Pidhatika B Mühlebach A Textor M 《Langmuir : the ACS journal of surfaces and colloids》2008,24(3):613-616
Surface coatings with so-called protein-repellent or nonfouling polymers have become indispensable for the development of modern therapeutic and diagnostic medical devices such as biosensors, drug-delivery capsules, and biomedical implants. Nowadays, poly(ethylene glycol) (PEG) is routinely used for these purposes. However, there is increasing evidence that PEG has limited long-term stability, particularly in vivo. Here we investigate poly(2-methyl-2-oxazoline) (PMOXA) as a potential alternative polymer. We designed comb copolymers consisting of a polycationic poly(l-lysine) backbone and PMOXA side chains by analogy to precisely studied and highly protein-repellent PEG-based systems. Using optical waveguide lightmode spectroscopy, we quantitatively compare the in situ self-assembly of the comb copolymers on negatively charged surfaces and the exposure of the formed monolayers to full human serum. We find that the PMOXA-based coatings with an optimal side-chain grafting density eliminate protein adsorption to a level of <2 ng/cm2; that is, they quantitatively equal the protein-repellent properties of the best PEG-based coatings. 相似文献
108.
The Synthesis of Organic Molecules of Intrinsic Microporosity Designed to Frustrate Efficient Molecular Packing 下载免费PDF全文
Dr. Rupert G. D. Taylor Dr. C. Grazia Bezzu Dr. Mariolino Carta Dr. Kadhum J. Msayib Dr. Jonathan Walker Dr. Rhys Short Dr. Benson M. Kariuki Prof. Neil B. McKeown 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(7):2466-2472
Efficient reactions between fluorine‐functionalised biphenyl and terphenyl derivatives with catechol‐functionalised terminal groups provide a route to large, discrete organic molecules of intrinsic microporosity (OMIMs) that provide porous solids solely by their inefficient packing. By altering the size and substituent bulk of the terminal groups, a number of soluble compounds with apparent BET surface areas in excess of 600 m2 g?1 are produced. The efficiency of OMIM structural units for generating microporosity is in the order: propellane>triptycene>hexaphenylbenzene>spirobifluorene>naphthyl=phenyl. The introduction of bulky hydrocarbon substituents significantly enhances microporosity by further reducing packing efficiency. These results are consistent with findings from previously reported packing simulation studies. The introduction of methyl groups at the bridgehead position of triptycene units reduces intrinsic microporosity. This is presumably due to their internal position within the OMIM structure so that they occupy space, but unlike peripheral substituents they do not contribute to the generation of free volume by inefficient packing. 相似文献
109.
We prove Lieb-Thirring inequalities for Schrödinger operators with a homogeneous magnetic field in two and three space dimensions. The inequalities bound sums of eigenvalues by a semi-classical approximation which depends on the strength of the magnetic field, and hence quantifies the diamagnetic behavior of the system. For a harmonic oscillator in a homogenous magnetic field, we obtain the sharp constants in the inequalities. 相似文献
110.
G.N. Greaves M.C. Wilding F. Kargl L. Hennet J.K.R. Weber Q. Vu Van P.F. McMillan 《Journal of Non》2011,357(2):435-441
By extending recent work on liquid-liquid transitions in supercooled yttria-alumina AYx liquids we draw attention to the compositional dependence of the structure factor of the high density liquid, arguing that this is sufficiently sensitive to discriminate between liquids at the level of a few %. Comparing structure factor differences between liquids of different compositions and in the same liquid AY20 between high and low temperatures straddling the transition at 1788 K between a high density liquid (HDL) and a low density liquid (LDL) enables compositional phase separation to be ruled out. It points instead to kinetic changes in polyhedral configurational order being the drivers for this polyamorphic transformation. Rotor behaviour observed in levitated liquid drops used in the high temperature experiments enables the reversibility of the LLT transition (LLT) and the associated changes in entropy and density to be identified. Evidence for critical-like behaviour in the structural relaxation time and in the fluctuation correlation length is presented. By re-examining recent work which failed to find the structural and thermal signatures for the LLT in liquid AY20 at 1788 K we present evidence for the LLT occurring instead in liquid AY15 at 1940 K, suggesting that the liquid-liquid transition temperature in AYx liquids decreases with increasing yttria content. 相似文献