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31.
(Styrene-p-chlorostyrene) triblock copolymers of the ABA and BAB types (A—polystyrene; B—poly-p-chlorostyrene) were prepared by anionic polymerization and their conformational behaviours in solutions were studied from measurements of the dipole moments. Two solvents, toluene and cumene, were used for the study; toluene is a good solvent for both polystyrene and poly-p-chlorostyrene whereas cumene is a selective solvent, good for polystyrene but poor for poly-p-chlorostyrene. It was found that the dipole moments of the block copolymers measured in toluene are the same for the ABA and BAB copolymers; in cumene however the dipole moment of the BAB copolymer is smaller than that of the ABA copolymer. The results give an additional support to our previous conclusion that the conformation of the block copolymers in a good solvent such as toluene could be approximated with a pseudo-random coil form; in a selective solvent, however, some anomalies take place in the conformation of the block copolymers, as deduced from intrinsic viscosity, osmotic pressure and light scattering measurements. 相似文献
32.
M Ogawa H Matsuda H Eto T Asaoka T Kuraishi A Iwasa T Nakashima K Yamaguchi 《Chemical & pharmaceutical bulletin》1991,39(9):2301-2307
A series of vinylimidazoles containing a hetero atom such as sulfur or oxygen at a beta-position of the vinyl group was prepared and the antifungal activities were tested. It was found that sulfur-substituted derivatives such as (E)-1-[2-(methylthio)-1-[2-(pentyloxy)phenyl]ethenyl]-1H-imidazole (5a-5) and (E)-1-[1-[2-(hexyloxy)phenyl]-2-(methylthio)ethenyl]-1H-imidazole (5a-6) showed excellent antifungal activities against dermatophytes and yeast cells. The stereochemistry of the hydrochloride salt of 5a-5 was determined by X-ray crystallography. The structure-activity relationships were discussed. 相似文献
33.
A mixture of Fe3S4 (greigite) and FeS2 (pyrite) is formed at 200°C on hydrothermal treatment of freshly precipitated iron sulphide. Its electron diffraction diagramm was recorded, which corresponded to an incomplete solid solution of Fe3S4 and FeS2. The surface and the interior of the spherical particles of the samples (size about 500 Å) consisted of Fe3S4 and FeS2, respectively. 相似文献
34.
Naoki KakusawaYoshinori Tobiyasu Shuji YasuikeKentaro Yamaguchi Hiroko SekiJyoji Kurita 《Tetrahedron letters》2003,44(47):8589-8592
The reaction of 12-arylethynyl-6-methyl-5,6,7,12-tetrahydrodibenzo[c,f][1,5]-azastibocines with organic halides such as acyl halides and aryl halides in the presence of PdCl2(PPh3)2 as a catalyst led to the formation of cross-coupling products, alkynyl ketones and diaryl acetylenes, in good yields. The reactivity of the ethynyl group on the 1,5-azastibocines was far superior to that on diphenyl(phenylethynyl)stibane, which brought about marked improvement in the reaction conditions (lower temperature and shorter reaction time) and in the yields of the cross-coupling products. Single-crystal X-ray analysis of the ethynyl-1,5-azastibocine showed the presence of intramolecular Sb?N interaction which should be responsible for the remarkable reactivity enhancement of the 1,5-azastibocines for this type of reaction. 相似文献
35.
Kizashi Yamaguchi 《International journal of quantum chemistry》1982,22(3):459-484
A generalization of the Hartree–Fock molecular orbital (MO) theory for treating diradical intermediates was explained pictorially by drawing molecular orbitals of diradical species such as ring-opened trimethylene. The generalized MO theory applied to elucidate electronic mechanisms of concerted, ionic, radical, and ion-radical reactions of organic reactants in the ground state. Generalized MO computations revealed the most essential characteristics of these reactions and mutal relationships between the worlds of Woodward–Hoffmann and Hughes–Ingold. Generalized MO studies supported our orbital symmetry, stability and pairing rules for concerted, ionic and radical reactions in the ground state, respectively. An extension of MO treatments to excited states reactions was briefly pointed out in relation to the density and spin correlation functions by the multireference CI wave functions. 相似文献
36.
Electronic structures and spectra of Hafner's hydrocarbons have been calculated by means of the semi-empirical SCF CI MO method incorporated with the variable bond-length technique. The results are in good agreement with experimental data. 相似文献
37.
The constitution of Grignard reagent, RMgCl (R = Me, tBu, Ph or benzyl), was investigated in the solid state by means of X-ray crystallography and in THF by coldspray ionization mass spectrometry (CSI-MS). Three types of crystal structures, (a) [Mg2(mu-Cl3)(THF)6](+)*[RMgCl2(THF)](-), (b) R2Mg4Cl6(THF)6, and (c) [2Mg2(mu-Cl3)(THF)6](+)*[R4Mg2Cl2]2-, were identified, and MeMg2(mu-Cl3)(THF)4-6 were detected as major species of MeMgCl in solution. 相似文献
38.
Miyauchi M Hoshino T Yamaguchi H Kamitori S Harada A 《Journal of the American Chemical Society》2005,127(7):2034-2035
A [2]rotaxane capped by a beta-cyclodextrin and a 2,4,6-trinitrophenyl group has been prepared by dissolving 6-aminocinnamoyl beta-cyclodextrin in water with 1-adamantane carboxylic acid and complexation with alpha-cyclodextrin followed by the reaction with 2,4,6-trinitrobenzene sulfonic acid sodium salt. The [2]rotaxane has been found to form supramolecular polymers by host-guest interactions. 相似文献
39.
Masahiro Kurokawa Hidemasa Yamaguchi Yuji Minoura 《Journal of polymer science. Part A, Polymer chemistry》1979,17(2):485-492
l-Menthyl vinyl ether (l-MVE) was homopolymerized and copolymerized with the monomers indene (IN) and acenaphthylene (ANp) by BF3OEt2 as a catalyst. The chiral menthyl substituent was cloven from the homopolymers and copolymers using dry-hydrogen bromide gas. After the removal of optically active menthyl group, poly(vinyl alcohol) (PVA) from l-MVE homopolymer was optically inactive, and copolymers (VA-IN, VA-ANp) from l-MVE-IN and l-MVE-ANp copolymers were still optically active. Hence, in the case of l-MVE homopolymer, it was concluded that asymmetric induction in the polymer main chain can only produce pseudoasymmetry. In the case of l-MVE-IN and l-MVE-ANp copolymers, it was found that asymmetric induction proceeded in the copolymer main chain and was caused by the influence of chiral menthyl group. 相似文献
40.
Pavel Smirnov Hisanobu Wakita Masaharu Nomura Toshio Yamaguchi 《Journal of solution chemistry》2004,33(6-7):903-922
The structure and complex formation of concentrated aqueous gallium(III) bromide (GaBr3) solutions have been investigated over a temperature range 80–333 K by Raman spectroscopy, X-ray absorption fine structure (XAFS), and X-ray diffraction. The Raman spectra obtained at various [Br?]/[Ga3+] molar ratios and temperatures have shown that complex formation between Ga3+ and Br? occurs as a predominant species, with [GaBr4]? at [Ga3+] as high as 1~2 M (M = mol?dm ?3) and [Br?]/[Ga3+] ratios > ~2, and that cooling of the solutions favors the formation of the aqua Ga3+. The intermediate species were not seen in the Raman spectra. The XAFS data have revealed that the aqua complex has a sixfold coordination as [Ga(H2O)6]3+ with a Ga3+–H2O distance of (1.96 ± 0.02) Å, whereas the [GaBr4]? complex has a Ga3+–Br? distance of (2.33± 0.02) Å, and that vitrification of the aqueous GaBr3 solution at liquid nitrogen temperature shifts the equilibrium toward the aqua complex. The X-ray diffraction data at different subzero temperatures have shown a tendency of decreasing Ga3+–Br? and increasing Ga3+–H2O interactions with lowering temperature, confirming the preference of aqua Ga3+ in the supercooled liquid state as well as in the glassy state. The Ga3+–H2O distance of ~1.8 Å for the tetrahedral coordination was found in a 2.01 M gallium(III) bromide solution with a [Br?]/[Ga3+] ratio of 3.7 and gradually increased to a value of 1.92 Å for octahedral geometry with decreasing temperature, suggesting that equilibrium shifts from [GaBr4]? to [Ga(H2O)6]3+ through intermediate species, [GaBr n ](3?n)+ (n = 2 and 3). The Ga3+–Br? and Br?–Br? distances within [GaBr4]? with an almost tetrahedral symmetry are (2.35± 0.02) and (3.82± 0.03) Å, respectively. The Ga3+ has the second hydration shell at (4.03± 0.03) Å and the hydration of Br? is characterized with a Br?–H2O distance of (3.35± 0.02) Å at all temperatures investigated. 相似文献