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91.
92.
Yoshimi Kurimura Masahiro Saito Kyota Hiramatsu Yoshihiro Sairenchi 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(9-11):1275-1292
Electron transfer reactions of Co(NH3)5PAA (PAA = polyacrylic acid) with either the polyanionic polymer-bound ferrous chelate, Fe11P-SS (P-SS = vinylbenzylaminediacetate-co-styrenesulfonate) or the uncharged polymer-bound ferrous chelate, Fe11P-VPRo (P-VPRo = vinylbenzylaminediacetate-co-vinylpyrrolidone), and the Ru(bpy)2+ 3 photosensitized reduction of Co(NH3)5PAA have been investigated in aqueous solutions at pH 5.4, I = 0.06 (I is ionic strength), and 25°C. For the ferrous chelate reductions, the second-order rate constants for Fe11-PSS and Fe11P-VPRo were almost equal to that for the corresponding nonpolymer-bound ferrous chelate, Fe11BDA (BDA = benzylaminediacetate). The results indicate that there is no appreciable steric hindrance due to the polymer chains of the polymer-bound ferrous chelates and that the effect of columbic repulsion force between the polyanion chains can be ignored for the reaction of Co(NH3)5PAA with Fe11P-SS. The results also suggest that there are two kinds of the pendant Co(III) species, “reactive” and “inert.” The inert Co(III) species are shielded by the polymer chains from attack of the Fe(II) chelates that are present in the bulk solutions. A similar reaction behavior was observed in the Ru(bpy)2+ 3 photosensitized reduction of Co(NH3)5PAA at pH 5.4. For the Co(III) complex having an extremely few Co(III) complex moieties on the polymer chain, almost all of the Co(III) groups were hardly reduced by the excited state of Ru(bpy)2+ 3, and reverse quenching occurred due to binding of the Ru(bpy)2+ 3 to the polyacrylic acid chain of the polymer complex. On the other hand, for Co(NH3)5PAA with a relatively large number of the Co(III) moieties on the polymer chain, lifetime measurements at a higher concentration of the Ru(bpy)2+ 3 showed a double-exponential fit, which suggests that there are two parallel decay processes. The fast and slow components mainly correspond to the decays: Ru(bpy)2+ 3 quenched by Co(III) and reverse quenching due to binding of Ru(bpy)2+ 3 into the compact polymer chains. 相似文献
93.
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95.
Yoshihiro Shigemasa Kuninori Oogaki Nasuo Ueda Ruka Hakashima Ken-Ichi Harada Naohito Takeda 《Journal of carbohydrate chemistry》2013,32(3):325-330
Abstract The formose reaction, by which a complex mixture of sugars and sugar alcohols (the so-called formose) are produced by the base-catalyzed condensation of formaldehyde, has received much attention in connection with the prebiotic synthesis of carbohydrates2 and the microbial utilization of formose.3–5 Formose, however, has not been useful yet, because of the complexity of this product mixture (Fig. 1a). Therefore, it seemed desirable to make the reaction more selective. 相似文献
96.
Yoshihiro Shigemasa Takaaki Ueda Hiroyuki Saimoto 《Journal of carbohydrate chemistry》2013,32(4):669-673
Abstract The formose reactions2 in N,N-dimethylformamide (DMF) catalyzed by 2-(dimethylamino)ethanol and thiamine hydrochloride, have been found to give rise to dihydroxyacetone and DL-glycero-tetrulose selectively at 1.1 M and 3.0 M of formaldehyde concentration, respectively. In our consecutive study on the formose reaction in DMF, it has been fortunately found that the distribution of products is able to be controlled by the amount of water added to the reaction mixture. We describe herein the first example of the favored formation of DL-2-C-hydroxymethyl-3-pentu-lose (GP-191) in the formose reaction using DMF-H2O solvent, and it's isolation and structure elucidation. 相似文献
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98.
Minoru Tanaka Masanobu Yoshinaga Satoshi Asano Yuko Yamashoji Yoshihiro Kawaguchi 《Fresenius' Journal of Analytical Chemistry》1992,343(12):896-900
Summary The enantiomeric separation ability of unmodified and methylated cyclodextrins (CDs) during capillary zone electrophoresis (CZE) was investigated using twelve dansylamino acids. Unmodified - and -CDs exhibited high enantioselectivities. -CD could scarcely separate the enantiomers before and after dimethylation, but obtained enantioselectivity after trimethylation. On the other hand, dimethylation of -CD removed much of its high enantioselectivity. Moreover, the chemical modifications produced a reverse in the migration order of the enantiomers. The inclusion of dansyl-DL-phenylalanine with CDs was evaluated using 600 MHz 1H NMR spectroscopy. 相似文献
99.
Intermolecular coupling reactions of 1,3-dienes and aldehydes via transmetalation of nickelacycle intermediate with (i)Bu(2)Al-acac were investigated. In the reactions, a linear adduct or a branched adduct was produced, depending upon the nature of 1,3-dienes and aldehydes, via two nickelacycles that were relatively stable among the four possible nickelacycles because of the equilibrium with pi-allynickel forms. 相似文献
100.
Datta S Kumar K 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,62(1-3):473-477
The isotropic component of Raman band for C=O stretching mode of acetophenone in solution was analyzed by estimating the correlation coefficient with reference to Lorentzian lineshape. In the intermediate region of solute/solvent concentration there is a sharp decrease in the correlation coefficient and there appears to be a transition from non-Lorentzian to Lorentzian lineshape. The vibrational relaxation rates have been estimated from the isotropic component of Raman band in different solvents. The rate is shown to be dependent on several macroscopic as well as microscopic properties of the solute-solvent system and intermolecular interactions. The hydrodynamic and dispersion forces appear to play a major role in determining the vibrational relaxation rate and the broadening of the bands. 相似文献