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11.
[reaction: see text]. The sum of the rate constants for solvolysis and 18O-scrambling of 4-MeC6H4(13)CH(Me)18OC(O)C6F5 in 50/50 (v/v) trifluoroethanol/water, k(solv) + k(iso) = 1.22 x 10(-5) s(-1), is larger than k(solv) = 1.06 x 10(-5) s(-1) for solvolysis of the unlabeled ester. This shows that the ion pair intermediate undergoes significant internal return. The data give k(-1) = 7 x 10(9) s(-1) for internal return by unimolecular collapse of the ion pair, which is significantly larger than k(Nu) = 5 x 10(8) M(-1) x s(-1) for bimolecular nucleophilic addition of carboxylate anions to 4-MeC6H4CH(Me)+. 相似文献
12.
Kazunori Takada Hiroya Sakurai Fujio Izumi Takayoshi Sasaki 《Journal of solid state chemistry》2004,177(1):372-376
Monolayer hydrate (MLH) NaxCoO2·y′H2O was obtained from superconducting bilayer hydrate (BLH) NaxCoO2·yH2O by partial extraction of H2O molecules between the CoO2 layers. Magnetization measurements indicated that electron densities in the CoO2 layer of the MLH phase remained unchanged after the water extraction. Nevertheless, superconductivity was completely suppressed in the MLH phase. This strongly suggests that the highly 2D nature in the BLH phase due to its thick insulating layers consisting of H2O molecules and Na+ ions plays an important role for inducing superconductivity. 相似文献
13.
Keita Hamasaki Asao Nakamura Akihiko Ueno Fujio Toda 《Journal of inclusion phenomena and macrocyclic chemistry》1992,13(4):349-359
The effects of -cyclodextrin (-CyD), heptakis(2,6-di-O-methyl)--cyclodextrin (DMCyD) and heptakis(2,3,6-tri-O-methyl)--cyclodextrin (TMCyD) ontrans-cis photoisomerization of 1-ethyl-4-(4-hydroxystyryl)pyridinium (POH) have been studied in aqueous solutions. The ratio of [cis]/[trans] for POH in the photostationary state at pH 8.54 was remarkably reduced by the presence of CyD or DMCyD. The reduction of the [cis]/[trans] ratio in the photostationary state was explained in terms of the shift of the equilibrium of POH
+
trans
PO
trans
+ H– toward PO
trans
formation. The binding constants of CyD and DMCyD for PO
trans
were 2.00- and 1.36-fold larger than those for POH
+
trans
, respectively. The binding constants of TMCyD for both species are much smaller than those of CyD and DMCyD. This result indicates that PO
trans
, which has a betain structure, forms stable complexes with CyD and DMCyD with its hydrophobic parts inside and the charged parts outside the CyD cavities. 相似文献
14.
Abstract The conformations of pyridinio-appended β-cyclodextrin (CDP+) and nicotinamide-appended β-cyclodextrin (CDNA+) were studied by NMR spectroscopy. The orientations of the pyridine residue of CDP+ and the nicotinamide residue of CDNA+ were determined by using a combination of NMR spectroscopic techniques. NMR spectra indicate that the shapes of the cavities of CDP+ and CDNA+ were changed after forming complexes. This change depended on the shape of the guest. CDNA+ could separate the 1H resonances at the Cβ position of racemic tryptophan into two sets of resonances for each enantiomer. 相似文献
15.
Yasuo Horikawa Takeshi Takeda Toshiki Takizawa Taro Akazawa Ryota Fujio Tatsuo Fujimaki 《Journal of polymer science. Part A, Polymer chemistry》1996,34(7):1183-1188
The anionic polymerization of 1,3-butadiene using a novel metalloidal anion initiator, triallylstannyllithium (TALi)-allyllithium (ALi), was studied. The TALi-ALi initiated anionic polymerization of 1,3-butadiene gave the star polymer along with the linear polybutadiene (PBD). The star polymer consisted of three PBD branches and a central tin atom. What is striking is a fact that the number-average molecular weights (Mn) and molecular weight distribution of three PBD branches and linear PBD were almost identical. A reversible chain transfer polymerization mechanism, which includes the equilibrium between tri(macroallyl)-stannyllithium and macroallylic anion, is proposed. © 1996 John Wiley & Sons, Inc. 相似文献
16.
17.
18.
Yoshio Iwakura Fujio Toda Yoshinori Torii Reiko Sekii 《Journal of polymer science. Part A, Polymer chemistry》1968,6(7):1877-1882
Polymers having thioether, thiolester, and amide linkages in each repeating unit of a polymer main chain were prepared by the polyaddition reaction of pseudoxazolones (2-isopropylidene-4-alkyl-3-oxazolin-5-ones) and dimercaptans. The polymers had inherent viscosities in a range of 0.08–0.22 and gave transparent films by solution casting. 相似文献
19.
20.
Tsukasa Ikeda Ryoichi Kojin Chul-joong Yoon Hiroshi Ikeda Masao Iijima Kenjiro Hattori Fujio Toda 《Journal of inclusion phenomena and macrocyclic chemistry》1984,2(3-4):669-674
Cyclodextrin (CD) has a hydrophobic cavity which acts like a binding site of an actual enzyme. But enzymatic turnover reaction did not occur in CD-catalyzed reactions. -CD was modified by a histamine group to attach a reactive functional group. -CD-histamine accelerates the hydrolysis of p-nitrophenyl acetate. Catalytic rate constant of this reaction is close to an actual enzyme, -chymotrypsin. Enzymatic turnover reaction is realized with this compound at around neutral pH value. 相似文献