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241.
The s-cis ? s-trans equilibrium of several enamino ketones and aldehydes, has been evaluated based on the results of aromatic solvent induced shift measurements and of protonation of the title compounds. In contrast to α,β-unsaturated ketones bearing no heteroatom, the Δδ3,cis value but not the Δδ3,trans, proved to be useful in conformational assignments. Protonation, which occurs mainly on oxygen, enhances the rotational barrier, thus enabling the observation of both rotamers at room temperature. Steric hindrance to conjugation enhances the rate of protonation at the carbon C2. 相似文献
242.
We consider some elementary proofs of local versions of CLARKSON 's inequalities and point out the fact that these inequalities can be generalized to hold for a much wider class of parameters. In particular it is easy to generalize our interpolation proof in various ways to higher dimensions. We point out explicitely some examples of such generalizations and we also prove some corresponding global versions. In this elementary way we obtain both new proofs of some previous results of this kind and also some new complements, unifications and further generalizations of these results. 相似文献
243.
The paper is concerned with order-topological characterizations of topological Riesz spaces, in particular spaces of measurable functions, not containing Riesz isomorphic or linearly homeomorphic copies of or .
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An easy and safe, though only moderately effective method is presented for preparing (diacetoxyiodo)arenes, ArI(OAc)2, from iodoarenes, ArI, using the commercially available and easily handled urea-hydrogen peroxide adduct (UHP) as the oxidant. The reactions take place in anhydrous AcOH/Ac2O/AcONa (a catalyst)mixtures, at 40 oC for 3.5 h to afford the purified ArI(OAc)2 in 37-78% yields. The fully interpreted (1)H- and (13)C-NMR spectra of the ArI(OAc)2 products are reported. 相似文献
247.
Lech Drewnowski 《manuscripta mathematica》1982,37(1):61-64
Every infinite dimensional Banach or Fréchet space X has a dense Baire (hence barrelled) subspace E of uncountable codimension such that every closed subspaee M of X with ME={0} is finite dimensional. This result solves negatively a problem raised recently by M. De Wilde and B. Tsirulnikov. 相似文献
248.
Roman Luboradzki Wiktor Kozminski Lech Stefaniak 《Journal of chemical crystallography》1993,23(2):133-141
An X-ray diffraction study is reported for four molecules of mesoionic 2,3-diphenyltetrazoles. The results confirm a dipolar mesoionic structure, aromatic character of the tetrazole ring and no conjugation between the phenyl and tetrazole rings. The geometry of the exocyclic group is discussed in detail. The molecular parameters of the compounds investigated are correlated with13C and15N nmr data. The results obtained are compared with similar structures which have already been studied. 相似文献
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Dual‐Input Regulation and Positional Control in Hybrid Oligonucleotide/Discotic Supramolecular Wires
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Dr. Miguel Ángel Alemán García Eva Magdalena Estirado Dr. Lech‐Gustav Milroy Prof. Dr. Luc Brunsveld 《Angewandte Chemie (International ed. in English)》2018,57(18):4976-4980
The combination of oligonucleotides and synthetic supramolecular systems allows for novel and long‐needed modes of regulation of the self‐assembly of both molecular elements. Discotic molecules were conjugated with short oligonucleotides and their assembly into responsive supramolecular wires studied. The self‐assembly of the discotic molecules provides additional stability for DNA‐duplex formation owing to a cooperative effect. The appended oligonucleotides allow for positional control of the discotic elements within the supramolecular wire. The programmed assembly of these hybrid architectures can be modulated through the DNA, for example, by changing the number of base pairs or salt concentration, and through the discotic platform by the addition of discotic elements without oligonucleotide handles. These hybrid supramolecular‐DNA structures allow for advanced levels of control over 1D dynamic platforms with responsive regulatory elements at the interface with biological systems. 相似文献