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61.
Yuji Naruse Atsushi Takamori Itsuki Nagasawa 《Phosphorus, sulfur, and silicon and the related elements》2020,195(7):523-525
AbstractWe previously designed and prepared the first molecules to exhibit observable CD spectra by n-σ* excitation, 2,6-dithiaspiro[3.3]heptane 2,6-dioxide. Spiro[3.3]heptane frameworks possess axial asymmetry due to puckering of 2 four-membered rings; the ring bonds are rich in p-character due to acute bond angles, which lowers the σ* energy levels. In contrast, the lone pairs are rich in s-character, which results in a good donor with conformational fixation. We expected that, instead of lone pairs as donating orbitals, the use of σ-electron-donating Si-Si bonds should result in UV absorption in the observable range (>180?nm), so that the Cotton effect could appear, at least partially, in that range. We designed 2,6-disilyl-2,6-disilaspiro[3.3]heptanes as models, and performed theoretical calculations to confirm our idea. 相似文献
62.
A rate equation for photodegradation was derived from Lambert-Beer's law and Grotthus-Draper's law: -dc/dt=k1(1-exp(-(k2c+k3(c0-c))))k2c/(k2c+k3(c0-c)) where c is the concentration of reactant, c0 is the initial concentration of reactant, t is time, k1 is the rate constant, and k2 and k3 are the absorption coefficient of reactant and its photodegradation product, respectively. In a case where the photodegradation products have no photoabsorption, k3 assumes the value of zero in the above general equation. In a case where the photodegradation products have the same spectrum and molar absorptivity as that of the reactant, k3 assumes the value of k2, and hence the photodegradation is not a first-order reaction; however, the equation itself gives the pseudo-first-order reaction rate equation. In a case where the concentration of reactant is high enough, the equation approaches a zero-order reaction rate equation. The photodegradation rate of nifedipine in solutions under a germicidal lamp, near an ultraviolet fluorescent lamp and a fluorescent lamp was analyzed using the above equation. The photodegradation rate was directly proportional to the amount of light absorbed, and fitted well with the equation. The above theoretical equation was substantiated by the photodegradation of nifedipine, and hence is expected to apply to other photosensitive drugs. 相似文献
63.
Toru Tachihara Susumu Ishizaki Yoshiko Kurobayashi Hiroshi Tamura Youichi Ikemoto Atsushi Onuma Keisuke Yoshikawa Tetsuya Yanai Takeshi Kitahara 《Helvetica chimica acta》2003,86(2):274-279
All possible stereoisomers of imine derivatives 1 – 4 , which have the characteristic roast odor of seafood, were synthesized. As a result of odor evaluation of all isomers, we found that each isomer has a different and characteristic odor of roasted seafood. 相似文献
64.
Hiroshi Ikeda Takumi Sugiyama Akihiko Ueno 《Journal of inclusion phenomena and macrocyclic chemistry》2007,57(1-4):83-87
A new chemosensor for larger guests was prepared. The new chemosensor bears hydrophobic units at the primary hydroxy side
and a dansyl unit at the secondary hydroxy side of β-cyclodextrin. Due to the hydrophobic units, the new chemosensor is sensitive
to large or slender guests such as SDS and insensitive to 1-adamantanol, which is a good guest for the natural β-CD. 相似文献
65.
Yoshihisa Kurasawa Tomoyoshi Hosaka Kazue Ikeda Yuko Matsumoto Aiko Ishikura Atsushi Takada Ho Sik Kim Yoshihisa Okamoto 《Journal of heterocyclic chemistry》1994,31(2):527-533
The 3-(arylhydrazono)methyl-2-oxo-1,2-dihydroquinoxalines 9–11 were synthesized by the reaction of the quinoxalines 6–8 with various p-substituted benzenediazonium salts. Compounds 9–11 showed the tautomeric equilibria between the hydrazone imine A and diazenyl enamine B forms in dimethyl sulfoxide media. The substituent effect on the tautomer ratios of A to B was studied by the nmr spectroscopy to clarify that the presence of the ester group R2 on the hydrazone carbon and electron-donating p-substituent R1 on the side chain benzene ring exhibited a tendency to increase the ratios of the tautomer A . 相似文献
66.
67.
Kotaro Hidea Hiroshi Maezawa Atsushi Ito Katsumi Kobayashi Yoshiya Furusawa Takashi Ito 《Photochemistry and photobiology》1986,44(3):417-419
The spectral throughput of a vacuum-ultraviolet irradiation system at the SOR-RING facility was examined with various combinations of aluminum-and gold-coated optical elements in a 2.2-m modified Wadsworth monochromator. We found that the optimum was a combination of an aluminum-coated collimating mirror, concave grating, and plane deflecting mirror, and a combination of a gold-coated collimating mirror, concave grating and an aluminum-coated plane deflecting mirror in the wavelength regions 190-110 nm and 110-50 nm, respectively. 相似文献
68.
Nishinaga T Yamazaki D Stahr H Wakamiya A Komatsu K 《Journal of the American Chemical Society》2003,125(24):7324-7335
Novel cyclopentadienyl (Cp)-alkali metal complexes 1-M and 2-M (M = Li, Na, K), in which the Cp ring is annelated with two bicyclo[2.2.2]octene units and substituted with a phenyl group for 1 and a tert-butyl group for 2, were synthesized, and their structures and dynamic behaviors were investigated by means of X-ray crystallography, dynamic (13)C NMR, and DFT calculations. The X-ray crystallography results indicated that 1-Li, 1-Na, and 2-Na form monomeric contact ion pairs (CIP) with three THF molecules coordinated to the metal atom. Also, in THF-d(8), all of the 1-M and 2-M form monomeric CIP in the ground state. However, variable-temperature (13)C NMR measurements of 1-M and 2-M in THF-d(8) demonstrated dynamic behavior in which the metal ion exchanges positions between the upper and lower faces of the Cp ring. From a study of the concentration dependence of the dynamic behavior, the exchange was found to proceed principally as an intramolecular process at concentration ranges lower than 0.2 M. The experimentally observed deltaG values for the intramolecular exchange process for all the 1-M and 2-M (except for 2-Li, whose intramolecular process was too slow to observe) were found to be quite similar in THF-d(8) solution and to fall within the range of 12-14 kcal mol(-)(1). Within this range, a tendency was observed for the deltaG values to increase as the size of the metal decreased. Theoretical calculations (B3LYP/6-31G(d)) afforded considerably large values as the gas-phase dissociation energy for 1-M (162.7 kcal mol(-)(1) for M = Li; 131.6 kcal mol(-)(1) for M = Na; 110.9 kcal mol(-)(1) for M = K) and for 2-M (170.0 kcal mol(-)(1) for M = Li; 137.5 kcal mol(-)(1) for M = Na; 115.4 kcal mol(-)(1) for M = K). These values should be compensated for by a decrease in the solvation energies for the metal ions with increasing size, as exemplified by the calculated solvation energy for M(+)(Me(2)O)(4), which serves as a model for metal ions solvated with four molecules of THF (-122.9 kcal mol(-)(1) for M = Li; -94.7 kcal mol(-)(1) for M = Na; -67.7 kcal mol(-)(1) for M = K). This compensation results in a small difference in the overall energy for dissociation of 1-M or 2-M in ethereal solutions, thus supporting the similar deltaG values observed for the intramolecular metal exchange. 相似文献
69.
Atsushi Itagaki Kazuki Nakanishi Kazuyuki Hirao 《Journal of Sol-Gel Science and Technology》2003,26(1-3):153-156
The phase separation behavior of gelling systems containing the mixture of 3-functional and 4-functional alkoxysilanes has been investigated. The relation between the starting composition and resultant macroporous morphology was examined using tetramethoxysilane (TMOS) and vinyltrimethoxysilane (VTMS) as starting alkoxysilanes, formamide (FA) as an additive, under an acidic condition. Up to TMOS:VTMS molar ratio of 0.5:0.5, the phase relation remained almost unchanged from that of pure TMOS system which exhibits morphology with well-defined co-continuous macropores in a very limited concentration region. On the VTMS-rich side typically TMOS:VTMS = 0.2:0.8, however, the co-continuous macroporous morphology was obtained in a broader composition range than those of either pure TMOS or VTMS system. A dome-like pseudo binary region was obtained with the two-phase region extending toward FA-rich direction. The domain size and pore volume of the gels with macroporous morphology could be controlled by alkoxide:water ratio and total solvent fraction, respectively. 相似文献
70.
Hirai A Matsui A Komatsu K Tanino K Miyashita M 《Chemical communications (Cambridge, England)》2002,(17):1970-1971
A highly regio- and stereoselective alpha-methylation reaction of gamma,delta-epoxy-alpha,beta-unsaturated esters was achieved by using a Me2Zn-CuCN reagent. 相似文献