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111.
112.
Shinichi Ueji Kazumi Nakatsu Hiroshi Yoshioka Kenji Kinoshita 《Tetrahedron letters》1982,23(11):1173-1176
The crystals of the title compound contain both intra- and inter-molecular OH?π hydrogen bonds (the first example of bifurcated OH?π bonds), the stereochemistry of which has been elucidated by an X-ray structure analysis; this bifurcated bond is also supported by the observation based on the IR spectrum of the crystals. 相似文献
113.
114.
Shinichi Yano Kenji Tadano Koichiro Aoki Naokazu Koizumi 《Journal of Polymer Science.Polymer Physics》1974,12(9):1875-1887
Dielectric properties of poly(vinylidene fluoride) have been studied in the frequency range 20 Hz to 1 MHz and between 100 and 220°C, during heating and cooling. The dielectric constant and loss change abruptly at the temperature Tm corresponding to the melting point. At lower frequencies, two types of ionic conductin are observed. One appears below Tm and is attributed to interfacial polarization. The other occurs above Tm and is related to electrode polarization. These results suggest that a crystalline polymer is a heterogeneous medium for ionic transport, while the melt is a homogeneous medium. From these results, the nature of ac ionic conduction in crystalline polymers is discussed. At high frequency, the α relaxation is observed below Tm. It is due to the molecular motion in the crystalline region and disappears at Tm. 相似文献
115.
A new formulation of the environment potential approach (EPA) is developed within the Hartree-Fock-Slater framework. As the results of illustrative applications to C5 cluster which is the smallest unit of diamond lattice, EPA is shown to annul efficiently the fictitious-surface effects which are inevitably brought into a finite-size-cluster model. 相似文献
116.
Eishun Tsuchida Shinichi Irie 《Journal of polymer science. Part A, Polymer chemistry》1973,11(4):789-799
In order to discuss the electrostatic-field effect on a polymer reaction, the quaternization of poly-4-vinylpyridine–benzyl chloride (system I) was compared to that of poly-γ-chloromethylstyrene–γ-picoline (system II). In these two systems, the reaction initially proceeded according to the simple second-order kinetics. However, after the degree of quaternization exceeded 20–30 mole-%, a deviation from simple second-order kinetics occurred. In system I negative deviation occurred, while in system II positive deviation occurred. These phenomena occurred even though the solvent or the initial concentrations of the reactants were changed. The reasons for these phenomena are given below. In system I, the quaternized pyridine nitrogens prevented the benzyl chloride from approaching the unquaternized pyridine nitrogens. However, in system II the free γ-picoline was attracted by the quaternized chloro-γ-methyl site. Furthermore, the point at which the deviation occurred was determined by the degree of chloromethylation. All these results suggest that the effect of an electrostatic field must be presumed in these two systems. 相似文献
117.
Saito S 《Chemical & pharmaceutical bulletin》2005,53(9):1069-1076
We discovered that the reactivity of some conjugated and electron-deficient hydrocarbons was quite different in the presence of transition metal catalysts. In this review we report our development and applications of the highly selective palladium and nickel-catalyzed cycloaddition reactions of unsaturated hydrocarbons such as conjugated enynes, electron-deficient allenes, and electron-deficient methylenecyclopropanes. Some homocoupling reactions as well as co-cyclization reactions were described. The efficient synthesis of 4--7 membered carbocycles was achieved. 相似文献
118.
A method of an electronic structure calculation of cluster is suggested. It consists of an “effective” potential with an electron to close the torn valence bonds which appear inevitably in a finite-size-cluster model. The method is applied to the C5 cluster representing the diamond lattice and is shown to be effective to nullify the pseudo-surface effects. 相似文献
119.
Shinichi Kotani 《Communications in Mathematical Physics》1985,97(3):443-452
In the multi-dimensional case it is shown that the increase of the topological support of the probability measure describing the randomness of potentials implies the increase of the spectrum. In the one-dimensional case the converse statement for the absolutely continuous spectrum is valid. Especially the spectrum (in general dimension) and the absolutely continuous spectrum (in one-dimension) are determined only by the topological support of the random potentials.Research partially supported by the USNSF under grant MCS-81-20833 相似文献
120.