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比较1,1-双(2-叔丁基砜乙基)十二烷基苯基砜(1)双碳负离子在不同条件下的环合反应结果,控制反应条件,在铁催化下可以生成偶联糁烯化的环烯产物(2)为主要产物;不加催化剂,加热回流反应得到分子内亲核取代反应产物环丙烷化合物(3)。 相似文献
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Cederwall B Moradi FG Bäck T Johnson A Blomqvist J Clément E de France G Wadsworth R Andgren K Lagergren K Dijon A Jaworski G Liotta R Qi C Nyakó BM Nyberg J Palacz M Al-Azri H Algora A de Angelis G Ataç A Bhattacharyya S Brock T Brown JR Davies P Di Nitto A Dombrádi Z Gadea A Gál J Hadinia B Johnston-Theasby F Joshi P Juhász K Julin R Jungclaus A Kalinka G Kara SO Khaplanov A Kownacki J La Rana G Lenzi SM Molnár J Moro R Napoli DR Singh BS Persson A Recchia F Sandzelius M Scheurer JN Sletten G 《Nature》2011,469(7328):68-71
Shell structure and magic numbers in atomic nuclei were generally explained by pioneering work that introduced a strong spin-orbit interaction to the nuclear shell model potential. However, knowledge of nuclear forces and the mechanisms governing the structure of nuclei, in particular far from stability, is still incomplete. In nuclei with equal neutron and proton numbers (N = Z), enhanced correlations arise between neutrons and protons (two distinct types of fermions) that occupy orbitals with the same quantum numbers. Such correlations have been predicted to favour an unusual type of nuclear superfluidity, termed isoscalar neutron-proton pairing, in addition to normal isovector pairing. Despite many experimental efforts, these predictions have not been confirmed. Here we report the experimental observation of excited states in the N = Z = 46 nucleus (92)Pd. Gamma rays emitted following the (58)Ni((36)Ar,2n)(92)Pd fusion-evaporation reaction were identified using a combination of state-of-the-art high-resolution γ-ray, charged-particle and neutron detector systems. Our results reveal evidence for a spin-aligned, isoscalar neutron-proton coupling scheme, different from the previous prediction. We suggest that this coupling scheme replaces normal superfluidity (characterized by seniority coupling) in the ground and low-lying excited states of the heaviest N = Z nuclei. Such strong, isoscalar neutron-proton correlations would have a considerable impact on the nuclear level structure and possibly influence the dynamics of rapid proton capture in stellar nucleosynthesis. 相似文献
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Elise Deunf Olivier Buriez Eric Labbé Jean-Noël Verpeaux Christian Amatore 《Electrochemistry communications》2009,11(1):114-117
The electrochemical behavior of a new cobalt–cyclodextrin (CD) complex was investigated, in dimethylformamide, from CoX2 (X = Br and BF4) in the presence of 1 equiv. 6-Deoxy-6-N-(2-methyliminopyridine)-β-cyclodextrin as ligand. Under these conditions, it was demonstrated for the first time, that the electrogenerated cobalt(I) species can be kinetically and thermodynamically stabilized. The electrochemical study of CoX2 in the presence of a related iminopyridine ligand (2-pyridyl-N-benzylmethylimine), in which the cyclodextrin (CD) group was replaced by a simple aryl moiety, allowed to highlight the crucial role of the CD in this unexpected stabilization. Importantly, this unprecedented result was only observed when both the iminepyridine and the CD moieties were together covalently attached. Importantly, the supramolecular stabilized low-valent cobalt species remained fairly reactive towards aromatic halides despite its intrinsic stability. This original work opens new opportunities for the development of more selective catalytic processes both in organic and aqueous media. 相似文献
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Aureau D Ozanam F Allongue P Chazalviel JN 《Langmuir : the ACS journal of surfaces and colloids》2008,24(17):9440-9448
The acid-base equilibrium at the surface of well-defined mixed carboxyl-terminated/methyl-terminated monolayers grafted on silicon (111) has been investigated using in situ calibrated infrared spectroscopy (attenuated total reflectance (ATR)) in the range of 900-4000 cm (-1). Spectra of surfaces in contact with electrolytes of various pH provide a direct observation of the COOH <--> COO (-) conversion process. Quantitative analysis of the spectra shows that ionization of the carboxyl groups starts around pH 6 and extends over more than 6 pH units: approximately 85% ionization is measured at pH 11 (at higher pH, the layers become damaged). Observations are consistently accounted for by a single acid-base equilibrium and discussed in terms of change in ion solvation at the surface and electrostatic interactions between surface charges. The latter effect, which appears to be the main limitation, is qualitatively accounted for by a simple model taking into account the change in the Helmholtz potential associated with the surface charge. Furthermore, comparison of calculated curves with experimental titration curves of mixed monolayers suggests that acid and alkyl chains are segregated in the monolayer. 相似文献
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Plochocka P Faugeras C Orlita M Sadowski ML Martinez G Potemski M Goerbig MO Fuchs JN Berger C de Heer WA 《Physical review letters》2008,100(8):087401
We have investigated the absorption spectrum of multilayer graphene in high magnetic fields. The low-energy part of the spectrum of electrons in graphene is well described by the relativistic Dirac equation with a linear dispersion relation. However, at higher energies (>500 meV) a deviation from the ideal behavior of Dirac particles is observed. At an energy of 1.25 eV, the deviation from linearity is approximately 40 meV. This result is in good agreement with the theoretical model, which includes trigonal warping of the Fermi surface and higher-order band corrections. Polarization-resolved measurements show no observable electron-hole asymmetry. 相似文献
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Jean-Bernard Baudin Marc Julia Christian Rolando Jean-Noël Verpeaux 《Tetrahedron letters》1984,25(30):3203-3204
α-sulfonyl litiated anions are oxidized by cupric carboxylates into β, β-unsaturated sulfones. Primary sulfones lead to pure trans-vinylic sulfones. 相似文献
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High beta poloidal tokamaks can confine plasma pressures an order of magnitude higher than their low beta poloidal counterparts. The theoretical stability of these high beta poloidal magnetohydrodynamics equilibria was left unresolved for many years. Using modern computational tools, such configurations are now found stable to Mercier, resistive and high-n (ideal and resistive) ballooning criteria as well as fixed and free-boundary modes for a wide range of current density profiles in the framework of a low field large-aspect-ratio machine. 相似文献