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Akihiro Wakisaka

Bio: Akihiro Wakisaka is an academic researcher from National Institute of Advanced Industrial Science and Technology. The author has contributed to research in topics: Solvation & Aqueous solution. The author has an hindex of 21, co-authored 83 publications receiving 1597 citations.


Papers
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Journal ArticleDOI
TL;DR: In this article, the present protocol is applied to the synthesis of the naturally occurring aromatase inhibitor (VII) and it is shown that it can be applied to a variety of applications.
Abstract: The present protocol is applied to the synthesis of the naturally occurring aromatase inhibitor (VII).

161 citations

Journal ArticleDOI
TL;DR: The microscopic structure observed through the mass-spectrometric analysis of clusters isolated from solution also shows good contrast between these binary mixtures as follows: methanol molecules have substitutional interaction with water clusters, while acetonitrile molecules have additional interaction with the water clusters as discussed by the authors.
Abstract: Water–methanol and water–acetonitrile, which show exothermic and endothermic mixing, respectively, represent good contrast in non-ideality of a binary mixture. The microscopic structure observed through the mass-spectrometric analysis of clusters isolated from solution also shows good contrast between these binary mixtures as follows: (1) methanol molecules have substitutional interaction with water clusters, while acetonitrile molecules have additional interaction with water clusters; (2) the clustering of methanol molecules are promoted in the presence of water; on the contrary, the acetonitrile clusters are disintegrated in the presence of water. Such findings could partially explain the non-ideality of these binary mixtures on the basis of the cluster structures.

140 citations

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TL;DR: In this article, the microscopic structures in ethanol-water binary mixtures were examined by analyzing the mass spectra of clusters generated through fragmentation of liquid droplets, from the effects of temperature and mixing ratios on the cluster structures.

124 citations

Journal ArticleDOI
TL;DR: The calculations suggest that the C-I and C-Br halogen bonds play an important role in controlling the structures of molecular assemblies, that theC-Cl bonds play a less important role and that C-F bonds have a negligible impact.
Abstract: The geometries and interaction energies of complexes of pyridine with C(6)F(5)X, C(6)H(5)X (X = I, Br, Cl, F and H) and R(F)I (R(F) = CF(3), C(2)F(5) and C(3)F(7)) have been studied by ab initio molecular orbital calculations. The CCSD(T) interaction energies (E(int)) for the C(6)F(5)X-pyridine (X = I, Br, Cl, F and H) complexes at the basis set limit were estimated to be -5.59, -4.06, -2.78, -0.19 and -4.37 kcal mol(-1) , respectively, whereas the E(int) values for the C(6)H(5)X-pyridine (X = I, Br, Cl and H) complexes were estimated to be -3.27, -2.17, -1.23 and -1.78 kcal mol(-1), respectively. Electrostatic interactions are the cause of the halogen dependence of the interaction energies and the enhancement of the attraction by the fluorine atoms in C(6)F(5)X. The values of E(int) estimated for the R(F)I-pyridine (R(F) = CF(3), C(2)F(5) and C(3)F(7)) complexes (-5.14, -5.38 and -5.44 kcal mol(-1), respectively) are close to that for the C(6)F(5)I-pyridine complex. Electrostatic interactions are the major source of the attraction in the strong halogen bond although induction and dispersion interactions also contribute to the attraction. Short-range (charge-transfer) interactions do not contribute significantly to the attraction. The magnitude of the directionality of the halogen bond correlates with the magnitude of the attraction. Electrostatic interactions are mainly responsible for the directionality of the halogen bond. The directionality of halogen bonds involving iodine and bromine is high, whereas that of chlorine is low and that of fluorine is negligible. The directionality of the halogen bonds in the C(6)F(5)I- and C(2)F(5)I-pyridine complexes is higher than that in the hydrogen bonds in the water dimer and water-formaldehyde complex. The calculations suggest that the C-I and C-Br halogen bonds play an important role in controlling the structures of molecular assemblies, that the C-Cl bonds play a less important role and that C-F bonds have a negligible impact.

111 citations

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TL;DR: In this article, the microscopic solvent structure of dimethyl sulfoxide-water mixtures and its influence on the solvation structure of solute from a clustering point of view, by means of a specially designed mass spectrometric system, was studied.
Abstract: We have studied the microscopic solvent structure of dimethyl sulfoxide-water mixtures and its influence on the solvation structure of solute from a clustering point of View, by means of a specially designed mass spectrometric system. It was observed that the propensity to the cluster formation is nonlinearly dependent on the solvent composition, exhibiting the existence of a critical value of mixing ratios where drastic changes in the microscopic solvent structure occur. It was also demonstrated that in such a solvent mixture the solvation structure of solutes such as 2-butanol, cyclopentanol, cyclohexanol, and phenol is greatly related to the microscopic solvent structures, implying that solute species interact with already established solvent clusters, rather than with individual solvent molecules.

93 citations


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01 Dec 1991
TL;DR: In this article, self-assembly is defined as the spontaneous association of molecules under equilibrium conditions into stable, structurally well-defined aggregates joined by noncovalent bonds.
Abstract: Molecular self-assembly is the spontaneous association of molecules under equilibrium conditions into stable, structurally well-defined aggregates joined by noncovalent bonds. Molecular self-assembly is ubiquitous in biological systems and underlies the formation of a wide variety of complex biological structures. Understanding self-assembly and the associated noncovalent interactions that connect complementary interacting molecular surfaces in biological aggregates is a central concern in structural biochemistry. Self-assembly is also emerging as a new strategy in chemical synthesis, with the potential of generating nonbiological structures with dimensions of 1 to 10(2) nanometers (with molecular weights of 10(4) to 10(10) daltons). Structures in the upper part of this range of sizes are presently inaccessible through chemical synthesis, and the ability to prepare them would open a route to structures comparable in size (and perhaps complementary in function) to those that can be prepared by microlithography and other techniques of microfabrication.

2,591 citations

Journal ArticleDOI
TL;DR: This workFloat their problematic reactions on water and to send observations of success or failure to us at onwater@scripps.edu for public dissemination with attribution.
Abstract: [*] Dr. S. Narayan, Dr. J. Muldoon, Prof. M. G. Finn, Prof. V. V. Fokin, Prof. H. C. Kolb, Prof. K. B. Sharpless Department of Chemistry and the Skaggs Institute of Chemical Biology The Scripps Research Institute 10550 North Torrey Pines Road La Jolla, CA 92037 (USA) Fax: (+ 1)619-554-6738 E-mail: sharples@scripps.edu [**] We thank Dr. Vladislav Litosh for carrying out preliminary work. Support from the National Institutes of Health, National Institute of General Medical Sciences (GM 28384), the National Science Foundation (CHE9985553), the Skaggs Institute for Chemical Biology, and the W. M. Keck Foundation is gratefully acknowledged. S.N. thanks the Skaggs Institute for a postdoctoral fellowship. We also thank Dr. Suresh Suri, Edwards Air Force Base, California, for a generous gift of quadricyclane. We urge our fellow chemists to float their problematic reactions on water and to send observations of success or failure to us at onwater@scripps.edu for public dissemination with attribution. Supporting information for this article is available on the WWW under http://www.angewandte.org or from the author. Angewandte Chemie

1,393 citations

Journal ArticleDOI
TL;DR: One of the goals of this Review is to attract the attention of the scientific community as to the benefits of using hypervalent iodine compounds as an environmentally sustainable alternative to heavy metals.
Abstract: The preparation, structure, and chemistry of hypervalent iodine compounds are reviewed with emphasis on their synthetic application. Compounds of iodine possess reactivity similar to that of transition metals, but have the advantage of environmental sustainability and efficient utilization of natural resources. These compounds are widely used in organic synthesis as selective oxidants and environmentally friendly reagents. Synthetic uses of hypervalent iodine reagents in halogenation reactions, various oxidations, rearrangements, aminations, C–C bond-forming reactions, and transition metal-catalyzed reactions are summarized and discussed. Recent discovery of hypervalent catalytic systems and recyclable reagents, and the development of new enantioselective reactions using chiral hypervalent iodine compounds represent a particularly important achievement in the field of hypervalent iodine chemistry. One of the goals of this Review is to attract the attention of the scientific community as to the benefits of...

1,228 citations

Journal ArticleDOI
TL;DR: In this article, the authors present a review of the research and development of low dosage hydrate inhibitors with emphasis on the chemical structures that have been designed and tested, and the mechanisms of both kinetic inhibitors and anti-agglomerants.
Abstract: Low dosage hydrate inhibitors (LDHIs) are a recent and alternative technology to thermodynamic inhibitors for preventing gas hydrates from plugging oil and gas production wells and pipelines. LDHIs are divided into two main categories, kinetic inhibitors (KHIs) and anti-agglomerants (AAs), both of which are successfully being used in field applications. This paper reviews the research and development of LDHIs with emphasis on the chemical structures that have been designed and tested. The mechanisms of both KHIs and AAs are also discussed.

939 citations