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581.
The flexoelectric effect of 4-heptyloxy-4'-cyanobiphenyl (7OCB) monolayers at the air-water interface is studied by Maxwell displacement current (MDC) and optical second harmonic generation measurements. Though MDC was expected to increase during the compression of 7OCB monolayers in L2L2' phase from the MDC theory developed previously, decrease of MDC was detected in these phases. This abnormalous phenomenon is found to be due to the quench of flexoelectric effect by the flow orientation of monolayers. 相似文献
582.
Takaaki Kawaguchi Fumio Sanda Toshio Masuda 《Journal of polymer science. Part A, Polymer chemistry》2002,40(22):3938-3943
The polymerization of isobutyl vinyl ether (IBVE) and tert‐butyl vinyl ether (TBVE) was carried out with metallocene and nonmetallocene catalysts, and the stereoregularity of the formed polymers was examined with 13C NMR spectroscopy. IBVE afforded polymers with 63–68% dyad isotacticity by polymerization with mixtures of metallocene catalysts and methyl aluminoxane as a cocatalyst in toluene as a solvent. However, TBVE yielded polymers with 47–52% dyad isotacticity (21–28% triad isotacticity) under the same conditions, the isotacticity being lower than that of poly(isobutyl vinyl ether) (PIBVE). Nonmetallocene catalysts, including Ti, Zr, and Hf complexes with two phenoxy imine chelate ligands, provided PIBVE and poly(tert‐butyl vinyl ether) with 63–68 and 45–51% dyad isotacticity, respectively. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3938–3943, 2002 相似文献
583.
This article reviews the present status of the application of transient or time-resolved Raman spectroscopy to the mechanistic studies of the cis—trans photoisomerization in conjugated molecules. Attention is focused on the vibrational information about the molecular structure of the electronically excited intermediates which are involved in the process of photoisomerization. Two examples, the trans to cis photoisomerization of stilbene through the lower excited singlet state and the cist to trans isomerization of retinal through the lowest excited triplet state, are included. 相似文献
584.
2-Phenylheptamethyltrisilane as a model compound of polysilastyrene was irradiated at a high dose (1440 kGy) of γ-rays without any additive. The trisilane was found to be resistant to γ-rays, while it gave small amounts of Me6Si2, Me3SiSiMe2Ph, Me3SiH, Me3SiSiHMePh and (Me3Si)2 SiMeC6H4SiMe3. These products can be interpreted as being due to a chain contraction of the trisilane with the extrusion of methylphenylsilylene, a methyl migration with the extrusion of dimethylsilylene, a scission of an Si–Si bond due to an attack by hydrogen atoms, and a substitution of a hydrogen atom on the phenyl group by a trimethylsilyl radical. The same reactions, except the chain contraction, are observed in the cases of pentamethylphenyldisilane and 1,2-diphenyltetramethyldisilane. On the basis of the data obtained, the chemical behavior of polysilastyrene during the irradiation is discussed. 相似文献
585.
Sumiyoshi T Nishimura K Nakano M Handa T Miwa Y Tomioka K 《Journal of the American Chemical Society》2003,125(40):12137-12142
A series of 10 didodecanoylamides of alpha,omega-alkylidenediamines bridged by a straight carbon chain varying in length from 0 to 9 carbons was examined as possible gelator molecules of organic liquids to gain information on the relationships between the spacial arrangement of two amide groups in a molecule and their effects on the microscopic structures of the gel. The structural characteristics of these amides are parallel and antiparallel arrangements of two amide carbonyl groups, which depend on the even and odd numbers of a bridging zigzag carbon chain. The linear alkyl chain moieties and a center carbon chain of diamides intermolecularly interact with each other within the van der Waals contact. Two amide moieties of an even number carbon chain diamide intermolecularly interact with each other by using two pairs of hydrogen bonds with two other molecules in a plane, which formed ribbonlike self-complementarily assembled aggregates. On the other hand, a diamide of an odd number carbon chain forms four independent hydrogen bonds with four other molecules not in a plane, which assembled into woven aggregates. Asymmetric introduction of a methyl group at the alpha-position of the amide groups successfully twists the two side chain van der Waals cores of the chiral diamides in the fixed direction, giving helically twisted ribbon and coiled coil aggregates. The helically twisted ribbon and coiled coil aggregates of these chiral diamides were directly observed by CD, SEM, and TEM, providing a basis for the design of a sophisticated small molecular gelator of a tailor-made shape. 相似文献
586.
The characteristics of lithium iodide-containing poly(ethylene glycol) as a gas chromatographic stationary phase have been evaluated in terms of partial free energy of transfer (delta G t0) from poly(ethylene glycol) to the lithium iodide-poly(ethylene glycol) system for a variaty of amides (n-fatty acid amides, lactams, benzamides, anilides, nicotinamides, isonicotinamides, barbiturates, pyrazolones) and several amines. The changes in relative retention and resolution of two solute peaks caused by the addition of lithium iodide to poly)ethylene glycol) are correlated with the difference in their delta Gt0 values. The application to the specific separation of some amidic drugs is demonstrated. 相似文献
587.
Takaaki Horaguchi Kohei Hasegawa Eietsu Hasegawa Takahachi Shimizu Kiyoshi Tanemura Tsuneo Suzuki 《Journal of heterocyclic chemistry》1992,29(2):503-509
Thiopyrano[4,3,2-cd]benzofuran 9 possessing benzofuran and methylenethiopyran structures in the molecule was synthesized starting from 1-chloro-4-methoxy-2-nitrobenzene 11. Some reactions (formylation, protonation and catalytic hydrogenation) on 9 were examined. The 2-position of 9 was highly reactive toward electrophilic reagents and the furan ring was readily reduced by catalytic hydrogenation with palladium-charcoal. Thiopyrano[4,3,2-cd]benzofuran 9 has both properties of methylenethiopyran and benzofuran. 相似文献
588.
Transient resonance Raman spectra of trans-stilbene in n-hexane have been obtained using two pulsed lasers at 266 and 585 nm. The former was used to pump the molecule to the first excited singlet state (S1) and the latter to proble spontaneous Raman scattering in resonance with the Sn ← S1 electronic transition. The dependence of the pump and probe laser power, the temporal behavior, and the excitation profile of the spectra clearly indicate that they are due to the S1 state of trans-stilbene. 相似文献
589.
Essam Mohamed Sharshira Haruki Iwanami Mutsuo Okamura Eietsu Hasegawa Takaaki Horaguchi 《Journal of heterocyclic chemistry》1996,33(1):137-144
Photocyclization reactions were carried out on ethyl 2-(8-oxo-5,6,7,8-tetrahydro-1-naphthyloxy)acetates 1a-e and ethyl 2-(5-oxo-6,7,8,9-tetrahydro-5H-benzocyclohepten-4-yloxy)acetates 2a-e in acetonitrile. Irradiation of 1a-e gave naphtho[1,8-bc]furanols 3a-e and naphtho[1,8-bc]furans 4a-e in 33–83% yields and ethyl acrylates 5b-d were produced in 3–25% yields during irradiation of 1b-d . On the other hand, 2a-e afforded cyclohepta[ad|benzofuranols 6a-e and cyclohepta[ad]benzofurans 7a-e in 44–87% yields. Ethyl acrylates 8b-d were also produced in 7–43% yields from irradiation of 2b-d . Substituent effects on photocyclization and reaction pathways are discussed. 相似文献
590.
The adsorption behaviour of forty-eight metals on DEAE-cellulose thin layers has been examined in aqueous phosphoric acid media. RF values are given as a function of phosphoric acid concentration over the range 0.01–1.0 M and are compared with those obtained in a similar manner with a crystalline cellulose, Avicel SF. Particularly strong retention on DEAE-cellulose occurred for Mo(VI), W(VI), Re(VII), the platinum group metals, Au(III) and Bi(III). Weak to moderate retention was also observed for several metals, such as V(V), Fe(III), Se(IV), In(III), the rare earths and U(VI), at lower concentrations of phosphoric acid (<0.1 M). 相似文献