The Experts below are selected from a list of 13908 Experts worldwide ranked by ideXlab platform
Tadaaki Yamagishi - One of the best experts on this subject based on the ideXlab platform.
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monofunctionalized pillar 5 arenes synthesis and supramolecular structure
Chemical Communications, 2011Co-Authors: Tomoki Ogoshi, Kazuki Demachi, Keisuke Kitajima, Tadaaki YamagishiAbstract:The first synthesis of a monohydroxy pillar[5]arene has been carried out, by controlling the de-O-methylation of per-methylated pillar[5]arene. Using monohydroxy pillar[5]arene as an intermediate, mono-guest-functionalized pillar[5]arene was prepared. It formed a self-inclusion complex in CDCl3 whereas in Acetone-D6 dethreading of the guest moiety took place.
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effect of an intramolecular hydrogen bond belt and complexation with the guest on the rotation behavior of phenolic units in pillar 5 arenes
Journal of Physical Chemistry Letters, 2010Co-Authors: Tomoki Ogoshi, Keisuke Kitajima, Tadaaki Yamagishi, Takamichi Aoki, Yoshiaki NakamotoAbstract:The rotation behavior of the phenolic units in pillar[5]arenes has been studied by means of the dynamic 1H NMR measurements. In Acetone-D6, the individual conformers of pillar[5]arene were observed under −60 °C, indicating that the rotation movement was slow on the NMR time scale under −60 °C. In permethylated pillar[5]arene in Acetone-D6, the peaks were not split even at −90 °C, strongly suggesting that the rotation movement was fast on the NMR time scale at −90 °C. This is due to the lack of the intramolecular hydrogen bond belt in permethylated pillar[5]arene. In the mixture of pillar[5]arene and viologen guest in Acetone-D6, the split peaks were found at −30 °C and did not change under −60 °C. By formation of the host−guest complex between pillar[5]arene and viologen guest, the rotation movement was slow on the NMR time scale under −30 °C and almost stopped under −60 °C.
Tomoki Ogoshi - One of the best experts on this subject based on the ideXlab platform.
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monofunctionalized pillar 5 arenes synthesis and supramolecular structure
Chemical Communications, 2011Co-Authors: Tomoki Ogoshi, Kazuki Demachi, Keisuke Kitajima, Tadaaki YamagishiAbstract:The first synthesis of a monohydroxy pillar[5]arene has been carried out, by controlling the de-O-methylation of per-methylated pillar[5]arene. Using monohydroxy pillar[5]arene as an intermediate, mono-guest-functionalized pillar[5]arene was prepared. It formed a self-inclusion complex in CDCl3 whereas in Acetone-D6 dethreading of the guest moiety took place.
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effect of an intramolecular hydrogen bond belt and complexation with the guest on the rotation behavior of phenolic units in pillar 5 arenes
Journal of Physical Chemistry Letters, 2010Co-Authors: Tomoki Ogoshi, Keisuke Kitajima, Tadaaki Yamagishi, Takamichi Aoki, Yoshiaki NakamotoAbstract:The rotation behavior of the phenolic units in pillar[5]arenes has been studied by means of the dynamic 1H NMR measurements. In Acetone-D6, the individual conformers of pillar[5]arene were observed under −60 °C, indicating that the rotation movement was slow on the NMR time scale under −60 °C. In permethylated pillar[5]arene in Acetone-D6, the peaks were not split even at −90 °C, strongly suggesting that the rotation movement was fast on the NMR time scale at −90 °C. This is due to the lack of the intramolecular hydrogen bond belt in permethylated pillar[5]arene. In the mixture of pillar[5]arene and viologen guest in Acetone-D6, the split peaks were found at −30 °C and did not change under −60 °C. By formation of the host−guest complex between pillar[5]arene and viologen guest, the rotation movement was slow on the NMR time scale under −30 °C and almost stopped under −60 °C.
Vasiliy A. Golubev - One of the best experts on this subject based on the ideXlab platform.
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tms self diffusion coefficients in the binary solvent carbon tetrachloride Acetone D6 1h pgse nmr experiment and random discrete displacements model of self diffusion
Journal of Molecular Liquids, 2020Co-Authors: Vasiliy A. GolubevAbstract:Abstract The tetramethylsilane (TMS) self-diffusion coefficients in the binary solvent carbon tetrachloride (CTC) – Acetone-D6 (A-D6) have been obtained by the pulsed gradient spin-echo nuclear magnetic resonance (PGSE NMR) method at 278, 298, and 318 K. The TMS self-diffusion coefficients increase as the A-D6 concentration and temperature become higher. The temperature dependences of the TMS self-diffusion coefficients at various concentrations of the binary solvent have been analysed based on the random discrete displacements model of self-diffusion presented in this paper. Within the framework of the proposed model, it is shown that the Arrhenius type of the temperature dependence of the self-diffusion coefficient (which is observed for TMS in this work) is a special case when the diffusion activation energy ED > kBT. In the opposite case, the temperature dependence of the self-diffusion coefficient tends to the form of the equation obtained for an ideal gas.
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the self diffusion of parabens methyl propylparaben and tetramethylsilane in the binary solvent carbon tetrachloride co solvent methanol d4 Acetone D6 at 278 298 and 318 k
Journal of Molecular Liquids, 2019Co-Authors: Vasiliy A. Golubev, D L GurinaAbstract:Abstract The self-diffusion of parabens (methylparaben, propylparaben) and tetramethylsilane in the binary solvents carbon tetrachloride – co-solvent (methanol‑d4, Acetone‑D6) has been investigated by the pulsed gradient spin-echo nuclear magnetic resonance (PGSE NMR) method in the range of temperatures from 278 to 318 K. The self-diffusion coefficients of paraben and tetramethylsilane increase as the concentration of Acetone‑D6 increases and have a minimum for paraben and an inflection point for tetramethylsilane when the methanol‑d4 concentration increases. Based on the Stokes-Einstein equation it is shown that the paraben hydrodynamic radius in the binary solvent Acetone‑D6 – carbon tetrachloride is practically independent of the Acetone‑D6 concentration and has a maximum in the binary solvent methanol‑d4 – carbon tetrachloride. This behavior in both cases is explained by the paraben self-association degree and the heteroassociation degree of paraben – co-solvent.
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self diffusion coefficients of coumaric and caffeic acids in tetrachloromethane Acetone D6 mixtures
Russian Journal of Physical Chemistry A, 2019Co-Authors: Vasiliy A. Golubev, D L GurinaAbstract:The self-diffusion of p-coumaric and caffeic acids in a binary tetrachloromethane–Acetone-D6 solution at low concentrations of the dissolved compound is studied via pulsed field gradient-spin echo 1H NMR at 278 and 298 K. According to the results, the self-diffusion coefficients of caffeic acid are lower than those of p-coumaric acid. The hydrodynamic radii of the acids in tetrachloromethane, calculated using the Stokes–Einstein equation, are lower than those in Acetone-D6. This behavior is due to an increase in the degree of acid–Acetone heteroassociation. Molecular association is also apparent from changes in the chemical shifts of protons in carboxyl and hydroxyl groups within molecules of the studied acids.
Keisuke Kitajima - One of the best experts on this subject based on the ideXlab platform.
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monofunctionalized pillar 5 arenes synthesis and supramolecular structure
Chemical Communications, 2011Co-Authors: Tomoki Ogoshi, Kazuki Demachi, Keisuke Kitajima, Tadaaki YamagishiAbstract:The first synthesis of a monohydroxy pillar[5]arene has been carried out, by controlling the de-O-methylation of per-methylated pillar[5]arene. Using monohydroxy pillar[5]arene as an intermediate, mono-guest-functionalized pillar[5]arene was prepared. It formed a self-inclusion complex in CDCl3 whereas in Acetone-D6 dethreading of the guest moiety took place.
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effect of an intramolecular hydrogen bond belt and complexation with the guest on the rotation behavior of phenolic units in pillar 5 arenes
Journal of Physical Chemistry Letters, 2010Co-Authors: Tomoki Ogoshi, Keisuke Kitajima, Tadaaki Yamagishi, Takamichi Aoki, Yoshiaki NakamotoAbstract:The rotation behavior of the phenolic units in pillar[5]arenes has been studied by means of the dynamic 1H NMR measurements. In Acetone-D6, the individual conformers of pillar[5]arene were observed under −60 °C, indicating that the rotation movement was slow on the NMR time scale under −60 °C. In permethylated pillar[5]arene in Acetone-D6, the peaks were not split even at −90 °C, strongly suggesting that the rotation movement was fast on the NMR time scale at −90 °C. This is due to the lack of the intramolecular hydrogen bond belt in permethylated pillar[5]arene. In the mixture of pillar[5]arene and viologen guest in Acetone-D6, the split peaks were found at −30 °C and did not change under −60 °C. By formation of the host−guest complex between pillar[5]arene and viologen guest, the rotation movement was slow on the NMR time scale under −30 °C and almost stopped under −60 °C.
Aleksej Turockin - One of the best experts on this subject based on the ideXlab platform.
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reversible generation of metastable enols in the 1 4 addition of thioacetic acid to α β unsaturated carbonyl compounds
Journal of Organic Chemistry, 2012Co-Authors: Lukas Hintermann, Aleksej TurockinAbstract:Addition of thioacetic acid to reactive α,β-unsaturated carbonyl compounds like acrolein or crotonaldehyde in Acetone-D6 generates metastable (E)- and (Z)-1-alkenols, which tautomerize slowly at ambient temperature. The 1,4-addition of thioacetic acid and crotonaldehyde to (Z)-3-(acetylsulfanyl)-1-propen-1-ol is reversible with Keq = 5.5 ± 0.5 L/mol. A concerted, cyclic 1,4-addition mode is proposed to explain the preferred (Z)-stereoselectivity in lower polarity, nonprotic solvents.
