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911.
The excess partial molar enthalpy of 1-propanol (1P), , was measured at 28 degrees C in the ternary mixture of 1P-1-butyl-3-methylimidazolium chloride ([bmim]Cl)-H(2)O in the H(2)O-rich composition range. From these data we evaluated what we call the 1P-1P enthalpic interaction function, . Its changes induced by addition of [bmim]Cl of the pattern of were used as a probe to elucidate the effect of [bmim]Cl on the molecular organization of H(2)O. It was found that the effect of Cl(-) was not conspicuous within this methodology, and the observed dependence is predominantly due to the hydration of [bmim](+). The changes in the x(1P)-dependence of were compared with those brought about by temperature increase, or by the addition of fructose or glycerol. It was found that the effect of [bmim](+) is similar to that of fructose or increased temperature. We speculate that in the H(2)O-rich composition region a number of H(2)O molecules are attracted to the delocalized positive charge of the imidazolium ring and the bulk of H(2)O is influenced in such a manner that the global hydrogen bond probability is reduced. 相似文献
912.
Suzuki M Yumoto M Kimura M Shirai H Hanabusa K 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(1):348-354
A family of L-lysine-based low-molecular-weight compounds with various positively charged terminals (pyridinium and imidazolium derivatives) was synthesized and its gelation behavior in water was investigated. Most of the compounds can be very easily synthesized in high yields (total yields >90 %), and they function as excellent hydrogelators that form hydrogels below 1 wt %; particularly, N(epsilon)-lauroyl-N(alpha)-[11-(4-tert-butylpyridinium)undecanoyl]-L-lysine ethyl ester (2 c) and N(epsilon)-lauroyl-N(alpha)-[11-(4-phenylpyridinium)undecanoyl]-L-lysine ethyl ester (2 d), which are able to gel water at concentration of only 0.2 wt %. This corresponds to a gelator molecule that entraps more than 20 000 water molecules. All hydrogels are very stable and maintain the gel state for at least 9 months. TEM observations demonstrated that these hydrogelators self-assemble into a nanoscaled fibrous structure; a three-dimensional network is then formed by the entanglement of the nanofibers. An FTIR study in [D(6)]DMSO/D(2)O and in CHCl(3) revealed the existence of intermolecular hydrogen bonding between the amide groups. This was further supported by a (1)H NMR study in [D(6)]DMSO/H(2)O. A luminescence study, in which ANS (1-anilino-8-naphtharenesulfonic acid) was used as a probe, indicated that the hydrogelators self-assemble into nanostructures possessing hydrophobic pockets at a very low concentration. Consequently, it was found that the driving forces for self-assembly into a nanofiber are hydrogel bonding and hydrophobic interactions. 相似文献
913.
Wakabayashi N Takeichi M Uchida H Watanabe M 《The journal of physical chemistry. B》2005,109(12):5836-5841
Oxygen reduction reaction (ORR) activity and H(2)O(2) formation at Pt(54)Fe(46), Pt(68)Co(32), and Pt(63)Ni(37) electrodes in 0.1 M HClO(4) solution at 20 to 90 degrees C were investigated by using a channel flow double electrode method. In the temperature range of 20-50 degrees C, the apparent rate constants k(app) for ORR at these electrodes were found to be 2.4-4.0 times larger than that at a pure Pt electrode, whereas their apparent activation energies of 41 kJ mol(-1) at -0.525 V vs E degrees (0.760 V vs RHE at 30 degrees C) were comparable to that at the Pt electrode. H(2)O(2) yield was ca. 1.0% at Pt(54)Fe(46) and ca. 0.16% at Pt(68)Co(32) and Pt(63)Ni(37) between 0.3 and 1.0 V vs RHE. The k(app) values at the alloy electrodes decreased with elevating temperature above 60 degrees C, and settled to almost the same values at the Pt electrode. The H(2)O(2) production was not detected at the alloy electrodes once heated at the high temperature in the solution, probably due to the thickening of the Pt skin-layer by a considerable dissolution of nonprecious metal components (Fe, Co, Ni) from the alloys. 相似文献
914.
Wakahara T Kobayashi J Yamada M Maeda Y Tsuchiya T Okamura M Akasaka T Waelchli M Kobayashi K Nagase S Kato T Kako M Yamamoto K Kadish KM 《Journal of the American Chemical Society》2004,126(15):4883-4887
Ce@C(82) is isolated by high-performance liquid chromatography (HPLC) and the cage symmetry is determined as C(2)(v)() by measuring the (13)C NMR spectra of its anion. The (13)C NMR peaks of [Ce@C(82)](-) show temperature-dependent shifts ascribed to the f electron remaining on the Ce atom. Both Ce@C(82) and [Ce@C(82)](-) are silent in electron spin resonance spectroscopy (ESR) because of the highly anisotropic g matrix as well as of the fast relaxation process originating from the orbital angular momentum of the f electron. This is the complementary relationship to the observation of the paramagnetic shift in (13)C NMR. [Ce@C(82)](-) has lower stability in air than [La@C(82)](-). 相似文献
915.
Ultrasonic absorption and velocity measurements in aqueous solution of iso-butyl cellosolve (ethylene glycol iso-butyl ether) as a function of the concentration are reported. The two relaxational absorptions have been attributed to the perturbation of the equilibria expressed by AB?A+B and Aα(1/n)An where A is the solute, B is the solvent, AB is the complex and A n is the solute aggregate. The rate constants for each step have been determined. From the concentration dependence of the maximum excess absorption per wave length, the enthalpy change and the volume change for the reaction between the solute and the solvent have been determined for aqueous solutions of butyl cellosolve (ethylene glycol n-butyl ether), iso-butyl cellosolve and propyl cellosolve (ethylene glycol n-propyl ether). The results are consistent with a hydrogen bonding reaction. The effect of the ethers on water structure are considered and it is clear that the fraction of water molecules which can hydrogen bond to the solute decreases with the increasing hydrophobicity of the solute. 相似文献
916.
Summary We define a notion of contact totally umbilical submanifolds of Sasakian space forms corresponds to those of totally umbilical
submanifolds of complex space forms. We study a contact totally umbilical submanifold M of a Sasakian space form
(c ≠ −3) and prove that M is an invariant submanifold or an anti-invariant submanifold. Furthermore we study a submanifold
M with parallel second fundamental form of a Sasakian space form
(c ≠ 1) and prove that M is invariant or anti-invariant.
Entrata in Redazione il 7 settembre 1976. 相似文献
917.
Time variation of radon daughters concentration in snowfall was measured continuously. The relations of radon daughters concentration in snowfall to the precipitation and to atmospheric radon daughters concentration were investigated. It has become clear that when precipitation is small, radon daughters concentration in snowfall is distributed in a wide range, and that the quantity of radon daughters brought to ground surface by snowfall is proportional to precipitation. Washout effect of the snowfall on atmospheric radon daughters was also investigated. 相似文献
918.
Masahiro Hasegawa Kunio Arai Shozaburo Saito 《Journal of polymer science. Part A, Polymer chemistry》1987,25(12):3231-3239
The encapsulation of fine inorganic powder was carried out with the soapless emulsion polymerization of methyl methacrylate in water in the presence of the powder, a layer of surfactant being adsorbed. The powder used was titanium dioxide. Surfactants added prior to the polymerization were sodium dodecyl sulfate, dodecyltrimethyl ammonium bromide, and polyoxyethylene sorbitan mono-oleate. The encapsulation state of the powder with polymer was closely related to the amount of surfactant adsorbed on the powder; and an amount of adsorption above a certain value was necessary for uniform encapsulation. Ionic surfactants were more useful than nonionic in the surfactants used, and could be adsorbed utilizing the electrostatic interaction between powder and the ionic end group. The combination of electric charges between the ionic end groups of surfactant and initiator was found to influence the molecular weight of capsulating polymer. 相似文献
919.
Reduction of α-benzyloxy acetylenic ketones with zinc borohydride afforded the erythro-acetylenic vicinal diols in 95% stereoselectivity, while reduction with K-selectride gave the isomeric threo-diols in 90% stereoselectivity. 相似文献
920.
High-resolution solid-state magic angle spinning 73Ge NMR spectra of hexavalent germanium compounds, i.e. diiodogermylene (1a) and bis(1-pyrrolyl)(meso-tetraphenylporphyrinato)germanium (3a), were determined. To the best of our knowledge, this is the first example of high-resolution solid-state 73Ge NMR spectra of hexacoordinated germanium nuclei. The symmetry requirement for observation of high-resolution solid-state 73Ge NMR spectra is discussed. 相似文献