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61.
Hajime Kabashima Hideto Tsuji Hideshi Hattori 《Reaction Kinetics and Catalysis Letters》1996,58(2):255-259
All the alkaline earth oxides exhibit activities for double, bond isomerization of 5-vinylbicyclo[2.2.1]hept-2-ene (VBH) to 5-ethylidenebicyclo[2.2.1]hept-2-ene (EBH) at a reaction temperature of 273 K. The order of the activity on the basis of unit weight of catalyst was CaO>MgO>SrO>BaO when compared under optimum pretreatment conditions. The E/Z ratio in the products is determined by the reaction temperature regardless of the type of catalyst; the ratios were 82/18 and 88/12 for the reaction temperatures of 323 and 273 K, respectively. 相似文献
62.
Oki Michinori Toyofuku Yoshitaka Sakaue Tatsuya Hirose Takanori Asakura Mitsuhiro Morita Nobuhiro Toyota Shinji 《Russian Journal of Organic Chemistry》2003,39(4):542-553
X-ray crystallography of the ap-form of the 1-(9-fluorenyl)-2-(2-methyl-2-oxiranyl)naphthalene has revealed that the carbon atom of the oxirane which is connected to the naphthyl group in this compound is almost planar. The specific structural features of the epoxy ring in this compound are caused by sterical effects and by the presence of a -system in the immediate vicinity of the oxirane ring. Certain differences have been found also in reactivity of rotational isomers of 2-X-substituted 1-[1-(9-fluorenyl)-2-naphthyl]ethyl cations (X = O, S, Se). At X = O arose more deprotonation product from the -position of the oxygen than in reactions of sulfur and selenium-containing analogs. Reactions of epoxides with zinc chloride almost exclusively gave the corresponding aldehydes. 相似文献
63.
Photons propagating in strong magnetic fields are subject to a phenomenon called the “vacuum birefringence” where refractive indices of two physical modes both deviate from unity and are different from each other. We compute the vacuum polarization tensor of a photon in a static and homogeneous magnetic field by utilizing Schwinger’s proper-time method, and obtain a series representation as a result of double integrals analytically performed with respect to proper-time variables. The outcome is expressed in terms of an infinite sum of known functions which is plausibly interpreted as summation over all the Landau levels of fermions. Each contribution from infinitely many Landau levels yields a kinematical condition above which the contribution has an imaginary part. This indicates decay of a sufficiently energetic photon into a fermion–antifermion pair with corresponding Landau level indices. Since we do not resort to any approximation, our result is applicable to the calculation of refractive indices in the whole kinematical region of a photon momentum and in any magnitude of the external magnetic field. 相似文献
64.
Dr. Chunlin Chen Prof. Zhongchang Wang Dr. Mitsuhiro Saito Dr. Tetsuya Tohei Prof. Yoshiro Takano Prof. Yuichi Ikuhara 《Angewandte Chemie (International ed. in English)》2014,53(6):1543-1547
Atomic‐resolution imaging of beam‐sensitive biominerals is extremely challenging, owing to their fairly complex structures and the damage caused by electron irradiation. Herein, we overcome these difficulties by performing aberration‐corrected electron microscopy with low‐dose imaging techniques, and report the successful direct atomic‐resolution imaging of every individual atomic column in the complex fluorapatite structure of shark tooth enameloid, which can be of paramount importance for teeth in general. We demonstrate that every individual atomic column in shark tooth enameloid can be spatially resolved, and has a complex fluorapatite structure. Furthermore, ab initio calculations show that fluorine atoms can be covalently bound to the surrounding calcium atoms, which improves understanding of their caries‐reducing effects in shark teeth. 相似文献
65.
66.
We developed a CZE method for simultaneous determination of pyridine-triphenylborane (PTPB) anti-fouling agent and its degradation products such as diphenylborinic acid (DPB), phenylboronic acid (MPB), and phenol in artificial seawater (ASW) with no extraction procedure. The ASW samples, in which 20 % (v/v) acetonitrile was added, were injected directly into the capillary using vacuum injection. As the background electrolyte, 60 mM sodium tetraborate adjusted to pH 9.8 was used. The LODs (S/N = 3) for PTPB, DPB, MPB, and phenol were, respectively, 55, 78, 126, and 30 μg L?1. The RSDs (n = 4) for analytes listed above were in the respective ranges of 2.7–5.7, 0.68–6.1, and 0.69–1.1 % for the peak area, peak height, and migration time. Simple degradation experiments were conducted to verify the usefulness of the proposed method. The PTPB samples dissolved in ASW were put in the open air, and rooms with and without light. The sample solutions were analyzed over time. We inferred that PTPB in ASW was more degraded by photolysis than by hydrolysis. The proposed CZE method has been demonstrated as a useful tool to elucidate the PTPB degradation process and its degradation products in ASW. 相似文献
67.
(+)-Boronolide and (+)-deacetylboronolide were synthesized using Pd-catalyzed CO insertion and lactonization as the key step. As to the 13C NMR data of (+)-deacetylboronolide, the assignment at C-6 position should be revised. 相似文献
68.
Dr. Yohei Hattori Tatsuya Maejima Yumi Sawae Jun-ichiro Kitai Prof. Masakazu Morimoto Dr. Ryojun Toyoda Prof. Hiroshi Nishihara Prof. Satoshi Yokojima Dr. Shinichiro Nakamura Prof. Kingo Uchida 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(50):11441-11450
The cyclization reaction of diarylethenes having an azulene ring occurs only via higher excited states. Novel diarylethenes having an azulene ring with a strong donor or acceptor were synthesized and examined in these reactions. A derivative having an electron-donating 1,3-benzodithiol-2-ylidenemethyl group at the 1-position of the azulene ring showed photochromism, whereas neither a derivative having a π-conjugated electron-donating group at the 3-position of the azulene ring nor derivatives having a π-conjugated electron-withdrawing group at the 1- or 3-position of the azulene ring showed any photochromism. The photoreactivities of these compounds were explained by calculating forces and bond orders on the excited states using density functional theory (DFT) and time-dependent (TD)-DFT. 相似文献
69.
The secondary radiation after resonant excitation of F center and its linear polarization P correlated to the polarization of resonant light have been measured for five alkali halides at low temperatures. In KC1, the spectrum of P over the whole Stokes region is divided into three successive regions, the depolarization range at the one-phonon Raman scattering, the near plateau range, and the depolarization range down to vanishing. The former two have common relevance to resonant energy and symmetries of coupled phonons. These relevances are interpreted adopting a configuration coordinate model for 2s- and 2p-like excited states. 相似文献
70.
Mitsuhiro Yoshimatsu Fumihiro Hatanaka 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3-4):1007-1010
Abstract β-Ethoxy-α-phenyltellanylvinyl lithiums were successfully generated in situ from phenyltellanylacetaldehyde diethyl acetal with lithium 2,2,6,6-tetrame-thylpiperidide (LTMP) and underwent methylation or nucleophilic addition with aldehydes and ketones. The successive dehydration of the allylic alcohols with trimethylsilyl trifluoromethanesulfonate (TMSOTf) gave α-phenyltellanyl α,β-unsaturated aldehydes, which transformed to some useful compounds. 相似文献