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971.
Universal Reaction Mechanism of Boronic Acids with Diols in Aqueous Solution: Kinetics and the Basic Concept of a Conditional Formation Constant
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Yuki Furikado Tomomi Nagahata Takuya Okamoto Dr. Tomoaki Sugaya Prof. Dr. Satoshi Iwatsuki Prof. Dr. Masahiko Inamo Prof. Dr. Hideo D. Takagi Prof. Dr. Akira Odani Prof. Dr. Koji Ishihara 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(41):13194-13202
To establish a detailed reaction mechanism for the condensation between a boronic acid, RB(OH)2, and a diol, H2L, in aqueous solution, the acid dissociation constants (${K{{{\rm BL}\hfill \atop {\rm a}\hfill}}}$ ) of boronic acid diol esters (HBLs) were determined based on the well‐established concept of conditional formation constants of metal complexes. The pKa values of HBLs were 2.30, 2.77, and 2.00 for the reaction systems, 2,4‐difluorophenylboronic acid and chromotropic acid, 3‐nitrophenylboronic acid and alizarin red S, and phenylboronic acid and alizarin red S, respectively. A general and precise reaction mechanism of RB(OH)2 with H2L in aqueous solution, which can serve as a universal reaction mechanism for RB(OH)2 and H2L, was proposed on the basis of (a) the relative kinetic reactivities of the RB(OH)2 and its conjugate base, that is, the boronate ion, toward H2L, and (b) the determined pKa values of HBLs. The use of the conditional formation constant, K′, based on the main reaction: RB(OH)2+H2L ${{\mathop \leftrightarrow \limits ^{K{_{1}}}_{}}}$ RB(L)(OH)?+H3O+ instead of the binding constant has been proposed for the general reaction of uncomplexed boronic acid species (B′) with uncomplexed diol species (L′) to form boronic acid diol complex species (esters, BL′) in aqueous solution at pH 5–11: B′+L′ ${{\mathop \leftrightarrow \limits ^{K{^\prime}}_{}}}$ BL′. The proposed reaction mechanism explains perfectly the formation of boronic acid diol ester in aqueous solution. 相似文献
972.
The jamaicamides, isolated in Jamaica from the cyanobacterium Lyngbya majuscula, are new mixed polyketide-peptides that are known to be sodium channel blockers. The polyketide moiety contains an (E)-vinyl chloride, an undetermined methyl stereocenter (C9), and an (E)-olefin. Herein, we report the synthesis of the (E)-olefin moiety of the polyketide of the jamaicamides utilizing a Kocienski–Julia coupling. Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file. 相似文献
973.
Kiyoshi Kobayashi Masateru Nishioka Koichi Sato Tomoya Inoue Satoshi Hamakawa Tatsuo Tsunoda 《Journal of Solid State Electrochemistry》2006,10(8):629-634
An oxygen-permeable composite constituted to oxide ionic conductor phase (Ce0.75Nd0.25O1.875) and oxide electronic conductor phase (Nd1.8Ce0.2CuO4) was prepared using the acetate pyrolysis method. Based on electrical conductivity measurements, total electrical conductivity
of 75 mol% Ce0.75Nd0.25O1.875–25 mol% Nd1.8Ce0.2CuO4 composite material was governed by the electronic conduction paths. With respect to the oxygen permeation properties, the
results showed that oxygen permeation properties were unexplainable by a simple composite rule using the electrical transport
properties of the bulk Ce0.75Nd0.25O1.875 and the bulk Nd1.8Ce0.2CuO4. 相似文献
974.
Tadashi Ii Satoshi Okuda Takashi Hirano Kazuo Tsujimoto Mamoru Ohashi 《Journal of mass spectrometry : JMS》1993,28(7):789-794
Secondary ion mass spectrometry (SIMS) of anomeric pairs of methyl 2-O- and 3-O-sulfo-D -glucopyranosiduronic acids and methyl 2-O- and 3-O-sulfo-D -glucopyranosides show the deprotonated molecule in the negative-ion mode and ammoniated and sodiated molecules in the positive-ion mode. The four isomers were distinguished from each other by linked scanning at constant B/E in negative- and positive-ion SIMS, which gave information characteristic of the position of the sulfate group and even the configuration of the anomeric methoxy group. The main fragmentation processes correspond to the loss of methanol and the elimination of SO3. 相似文献
975.
To investigate the effect of exposure duration on stereopsis and its spatial frequency dependency, we measured disparity threshold for the depth discrimination varying stimulus exposure duration between 0.05 and 2 s for three spatial frequencies (0.23, 0.94 and 3.75 c/deg). The results showed that disparity threshold decreased with increase in exposure duration up to a certain duration, beyond which it was approximately constant (the duration is called critical duration). The critical duration was about 150 ms for gratings with low and middle spatial frequencies (0.23 and 0.94 c/deg) while the duration was about 750 ms for gratings with high spatial frequency (3.75 c/deg). This suggests that temporal integration property varies dependently on stimulus spatial frequency. We also attempted to relate the spatial frequency dependency of the temporal integration property to the differences in temporal frequency tuning to different spatial frequency stimuli. 相似文献
976.
Satoshi Masaki 《Annales Henri Poincare》2007,8(6):1037-1069
We study the semi-classical limit of the Hartree equation, which has focusing at a point. There exists a critical index indicating
nonlinear effect around the caustic, and it is known that the influence by the nonlinearity is negligible in subcritical case
(called linear caustic case), and that it is not in critical case (nonlinear caustic case). We give the asymptotic behavior
beyond caustic in some supercritical cases which give rise to very strong nonlinear effect.
Submitted: August 25, 2006. Accepted: December 11, 2006. 相似文献
977.
‘Fractal’ functions are formulated as a minimal cocycle on a topological dynamics which admits nontrivial scaling transformations.
In this paper, it is proved that if in addition it admits a continuous family of scaling transformations, then itscapacity is not ino(N
2). We define minimal cocycles with nontrivial scaling transformations coming from substitutions on a finite alphabet which
are proved to have capacityO(N), so that they admit only a discrete family of scaling transformations. We also construct one which has capacityO(N
2) and admit a continuous family of scaling transformations.
Supported by C.N.R.S.(U.R.A 225); Partially supported by the Japan Society for the Promotion of Science. 相似文献
978.
979.
A double fiber-optic Mach-Zehnder interferometer for sensing magnetic fields is devised using two polarization maintaining single-mode fibers. This sensor achieves not only highly sensitive performance but also excellent immunity from temperature disturbance. The sensitivity attains 243 deg/mT (mT=10-3N/A) for the sensing part of the 5 cm long fiber. 相似文献
980.
Masaki Narisawa Satoshi Kida Toshio Simoo Kiyohito Okamura Yasuo Kurachi 《Journal of Sol-Gel Science and Technology》1995,4(1):31-35
Precursor fibers for titanium carbide-carbon fibers were synthesized by reacting phenolic resin fibers with titanium isopropoxide (TIP). In this system, titanium oxide gel coated fiber was prepared by hydrolyzing TIP infiltrated resin fiber. The precursor fibers obtained after the hydrolysis were converted into titanium oxide-carbon fibers (TiO2-C fibers) by pyrolysis at 1273 K. The TiO2-C fibers were converted into titanium carbide-carbon fibers (TiC-C fibers) by heat treatment at 1373–1973 K. The mechanisms of the conversion from TiO2-C fibers to TiC-C fibers were characterized by TGA. 相似文献