排序方式: 共有13条查询结果,搜索用时 15 毫秒
1.
Ling KQ Lee Y Macikenas D Protasiewicz JD Sayre LM 《The Journal of organic chemistry》2003,68(4):1358-1366
Although copper(II)-mediated oxidation of phenols results in oxidative coupling rather than in oxygenation, it was recently reported that naturally occurring 5-alkylresorcinols undergo oxygenation in the presence of copper(II). To explore the generality of this reaction, the copper(II)-mediated autoxidation of 4-tert-butylresorcinol and 4,6-di-tert-butylresorcinol was investigated and was found to result in direct oxygenation at open activated positions and, at the tert-butyl-substituted positions, in oxygenation with competing loss of (as isobutylene) and 1,2-rearrangement of the tert-butyl group. 5-tert-Butyl-2-hydroxy-1,4-benzoquinone is the major product from both starting materials, and the final product mixture reflects, in part, coupling of metastable initially formed electrophilic and nucleophilic side products. Mechanisms that are consistent with the observed products and control reactions are proposed. The key step appears to be equilibration of a copper(II)-resorcinolate with a charge-transfer radical form that reacts regioselectively with O(2) as prescribed by resonance. 相似文献
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In this paper the response of an amperometric biosensor at mixed enzyme kinetics and diffusion limitations is modelled in
the case of the substrate and the product inhibition. The model is based on non-stationary reaction–diffusion equations containing
a non-linear term related to non-Michaelis–Menten kinetics of an enzymatic reaction. A numerical simulation was carried out
using a finite difference technique. The complex enzyme kinetics produced different calibration curves for the response at
the transition and the steady-state. The biosensor operation is analysed with a special emphasis to the conditions at which
the biosensor response change shows a maximal value. The dependence of the biosensor sensitivity on the biosensor configuration
is also investigated. Results of the simulation are compared with known analytical results and with previously conducted researches
on the biosensors. 相似文献
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Renckens TJ Janeliunas D van Vliet H van Esch JH Mul G Kreutzer MT 《Lab on a chip》2011,11(12):2035-2038
We demonstrate a rapid fabrication procedure for solvent-resistant microfluidic devices based on the perfluoropolyether (PFPE) SIFEL. We carefully modified the poly-dimethylsiloxane (PDMS) micromolding procedure, such that it can still be executed using the standard facilities for PDMS devices. Most importantly, devices with a thin SIFEL layer for the patterned channels and a PDMS support layer on top offered the best of two worlds in terms of chemical and mechanical stability during fabrication and use. Tests revealed that these devices overcome two important drawbacks of PDMS devices: (i) incompatibility with almost all non-aqueous solvents, and (ii) leaching of oligomer into solution. The potential of our device is shown by performing a relevant organic synthesis reaction with aggressive reactants and solvents. PFPE-PDMS devices will greatly expand the application window of micromolded devices. 相似文献
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Y Yang VO Kennedy JB Updegraph B Samas D Macikenas B Chaloux JA Miller EM Van Goethem ME Kenney 《The journal of physical chemistry. A》2012,116(34):8718-8730
Crystal structures have been determined for the three-member set of cofacial silicon phthalocyanines, ((n-C(6)H(13))(3)SiO)[SiPcO](1-3)(Si(n-C(6)H(13))(3)). The staggering angles between adjacent rings in the dimer and trimer of this set are ~16°. The interactions leading to these angles have been investigated by the atoms-in-molecules (AIM) and reduced-density-gradient (RDG) methods. The results show that long directional interactions (LDIs) are responsible for these angles. A survey of the staggering angles in various cofacial phthalocyanines described in the literature has revealed the existence of significant LDIs in a number of them. It is apparent that in many cases the ability of LDIs to dominate the forces giving rise to the staggering angles observed in cofacial phthalocyanines depends on their inter-ring separations. 相似文献
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van Rijn P Janeliunas D Brizard AM Stuart MC Eelkema R van Esch JH 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(45):13417-13428
In this study the possibility to control the size and shape of self-assembled structures through the local curvature of their molecular building blocks has been investigated. To this end a series of amphipathic conjugated oligothiophenes with a well-defined curvature of their backbone has been designed and synthesized. The molecular (local) curvature of these oligothiophenes resulted from a preference for cis instead of trans conformations at specific positions along the oligothiophene backbone, which can be controlled by the sequence of hydrophilic and hydrophobic groups, while their ratio was kept constant. The self-assembly of ter-, sexi-, and dodecathiophenes appeared to be a low-cooperative process, involving the formation of premicellar aggregates at sub-millimolar concentrations, which at concentrations in the millimolar regime transformed into micelles and cylindrical micelles. The aggregates display fine structures with dimensions reminiscent of the thiophene molecules. The structure-morphology relationship of the ter- and sexithiophenes could be described by conventional packing theory. However, with the dodecathiophene, the backbone curvature governed the formation of cylindrical aggregates with a well-defined diameter. These results demonstrate that it is possible to control the aggregation morphology of simple amphipathic oligothiophenes by implementation of an additional structural motif namely, the curvature. 相似文献
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Yang Y Samas B Kennedy VO Macikenas D Chaloux BL Miller JA Speer RL Protasiewicz J Pinkerton AA Kenney ME 《The journal of physical chemistry. A》2011,115(45):12474-12485
Single crystal structures have been determined for the three cofacial, oxygen-bridged, silicon phthalocyanine oligomers, [((CH(3))(3)SiO)(2)(CH(3))SiO](SiPcO)(2-4)[Si(CH(3))(OSi(CH(3))(3))(2)], and for the corresponding monomer. The data for the oligomers give structural parameters for a matching set of three cofacial, oxygen-bridged silicon phthalocyanine oligomers for the first time. The staggering angles between the six adjacent cofacial ring pairs in the three oligomers are not in a random distribution nor in a cluster at the intuitively expected angle of 45° but rather are in two clusters, one at an angle of 15° and the other at an angle of 41°. These two clusters lead to the conclusion that long, directional interactions (LDI) exist between the adjacent ring pairs. An understanding of these interactions is provided by atoms-in-molecules (AIM) and reduced-density-gradient (RDG) studies. A survey of the staggering angles in other single-atom-bridged, cofacial phthalocyanine oligomers provides further evidence for the existence of LDI between cofacial phthalocyanine ring pairs in single-atom-bridged phthalocyanine oligomers. 相似文献
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Dainius Janeliunas 《Tetrahedron》2009,65(40):8407-1532
An efficient synthetic method for 3,6-epoxy[1,5]dioxocines via the condensation of salicyl aldehydes and epichlorohydrin, using benzyl triethylammonium chloride as catalyst, is described. The use of neutral or electron-deficient salicyl aldehydes in all cases was found to give 3,6-epoxy[1,5]dioxocine derivatives in good yields. The structural features were resolved by IR, NMR spectroscopy, mass spectrometry, and ultimately proved by X-ray crystallographic analysis. 相似文献