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131.
Treatment of diphenylchloroborane with 1 equiv of pyridine or pyridine-N-oxide in CD2Cl2 formed the corresponding 1:1 adduct, which gave tricoordinate diphenylboron cation by electrophilic abstraction of chloride ion with the strong Lewis acid, SbCl5. The experimental 11B chemical shifts were in good agreement with the ab initio calculation results and the optimized structures were well explicable by 11B, 13C, and 121Sb NMR spectroscopy. 相似文献
132.
Fujio M Keeffe JR More O'Ferrall RA O'Donoghue AC 《Journal of the American Chemical Society》2004,126(32):9982-9992
Equilibrium constants are reported for the ionization of benzylic alcohols to carbocations stabilized by cyclic or acyclic o-alkyl or o-oxygen substituents. The measurements were stimulated by the observation of small or inverse effects of replacement of an o-CH2 group by O or S in the cyclopentyl ring of indanol (kO/kCH2 = 1.2) or in the cyclohexyl ring of tetralol (kO/kCH2 = 0.6, kS/kCH2 = 0.3) on rates of carbocation formation. Values of pKR (KR = [ROH][H+]/[R+]) have been obtained by combining rate constants, kH, for the acid-catalyzed ionization of the alcohols with kH2O for attack of water on the carbocation measured by the azide clock method. For carbocations derived from the following alcohols, values of pKR are as indicated: 1-indanol, -11.7; 2,3-dihydro-3-hydroxybenzofuran (benzofuran hydrate), -9.3; 1-tetralol, -12.2; 4-chromanol, -12.0; 4-thiochromanol, -12.3; o-methyl-1-phenylethanol, -13.8; o-methoxy-1-phenylethanol, -11.7. The measurements show that, in contrast to its small kinetic effect, the equilibrium effect of replacing the o-CH2 group by O in the cyclopentyl ring of indanol is 250-fold, whereas the effect of the same replacement in the cyclohexyl ring of tetralol is only 1.6. It is concluded (a) that the efficiency of conjugation of annular o-oxygen substituents to a benzylic carbocation center is sensitive to conformational restrictions arising from ring strain and (b) that, in the case of indanol, the kinetic effect of the same oxygen atom is subject to an imbalance of favorable resonance and unfavorable inductive effects at the transition state. 相似文献
133.
Transport in Porous Media - An analytical and numerical study was made on thermally developing forced convective flow in a channel filled with a fluid-saturated porous medium, subject to constant... 相似文献
134.
Graphite intercalated by AsF5 has been reported to give compounds of formula C8nAsF5 where n is the stage. It is doubtful however if materials of exact composition C8nAsF5 have ever been obtained. The intercalation of graphite by AsF5 is associated with electron oxidation of the graphite according to the equation: 3AsF5 + 2e? → 2AsF6? + AsF3. Because of the easy removal or displacement of AsF3 the As:F ratio is readily increased beyond 5. By treating graphite with excess AsF5, removing volatiles under vacuum and repeating the cycle seven times a first stage salt C10+AsF6? (Co = 7.96 ā) is made. Interaction of graphite with AsFs in the molar ratio 8:1, within a small volume reactor, yields a material of approximate composition C8AsF5. The major component of the volatiles at the onset of their removal is AsF5,, but, at a composition close to C10AsF5, is AsF3. ‘Graphite AsF5’ can be prepared by adding AsF3 to CxAsF6 salts. The electrical conductivities of ‘AsF5’ and AsF6 relatives will be compared and discussed. 相似文献
135.
Hirohisa Kishino Hidehiro Kato Fujio Kasamatsu Yoshihiro Fujise 《Annals of the Institute of Statistical Mathematics》1991,43(3):435-453
To get reliable information of the age structure of whale population, Japan conducted a feasibility study of scientific research in the Antarctic in 1987/88. Though the sample was not large enough, it was the first data free from the problem of selectivity and whaling ground bias. From the analysis, it was found that the biological characteristics are highly heterogeneous spatially or other ways. Considering this, we recognize that the survey should be designed to collect the sample from the whole research area uniformly to obtain unbiased estimates of population characteristics. However, in an actual biological field survey, it is difficult to keep the sampling fractions thecisely the same for each sampling units. Therefore, it is important to detect the heterogeneity in the sample, and poststratify the data corresponding to the heterogeneity. The methodology of the estimation and model evaluation presented here will be useful for the development of biological field survey in general. 相似文献
136.
Yuho Tsuno Kimito Funtasu Yasuyuki Maeda Masaaki Mishima Mizue Fujio 《Tetrahedron letters》1982,23(28):2879-2882
The substituent effect on the acetolysis of neophyl brosylates was analyzed successfully based on the analysis method of Yukawa-Tsuno. The basic concept of this method was strongly supported. 相似文献
137.
Shunsuke Fujio Yoshiharu Takamuki Fujiko Iwasaki Haruki Niwa Takashi Hirano 《Tetrahedron letters》2004,45(46):8531-8534
Phenyl-substitution to the C8 position of an imidazopyrazinone ring resulted in the significant bathochromic shift of the lowest energy band, while the substitution to the C6 position does not produce such a shift. This provides evidence that a color variation range of the solvatochromism of 2-phenylimidazopyrazinone derivatives depends strongly on the position of phenyl-substitution. Results indicated that an imidazopyrazinone with the phenyl groups at the C2 and C8 positions acts as a potential indicator of the proton donor ability of solvents. 相似文献
138.
Tsukasa Ikeda Ryoichi Kojin Chul-joong Yoon Hiroshi Ikeda Masao Iijima Fujio Toda 《Journal of inclusion phenomena and macrocyclic chemistry》1987,5(1):93-98
We modified cyclodextrin (CD) by a histamine group to make a model of -chymotrypsin. Enzymatic turnover reaction was realized with CD-histamine at around neutral pH value. Compared with amino-CD, it is ascertained that this catalytic activity of CD-histamine is caused by an imidazole group. Using several substrates in the hydrolytic reactions, it shows that CD-histamine has a structural selectivity for substrates which are structurally different to each other. 相似文献
139.
140.
Ryo Ishii Tetsuji Itoh Takuji Yokoyama Shun-ichi Matsuura Tatsuo Tsunoda Satoshi Hamakawa Fujio Mizukami Taka-aki Hanaoka 《Journal of Non》2012,358(14):1673-1680
A novel mesoporous silica (TMPS) was synthesized via self-assembly using a myristic acid ester of pentaglycerol. The ester is obtained from catalytic esterification and it is commercially available as a food grade emulsifier. TMPS material was employed for preparation of a biocatalyst in order to examine the ability as an enzyme support in comparison with the other mesoporous silica materials having a channel or a cage-like pore system. The used TMPS materials possessed the interconnected channel-like pore system with the pore sizes of 9.2, 12, and 16 nm. The materials successfully entrapped lipase into their mesopores with the high loadings. The resultant lipase/TMPS conjugates functioned as the biocatalyst for hydrolysis of p-nitrophenyl propionate (p-NPP), having the higher activity than those of the used mesoporous silica conjugates. The high activities were ascribed to the textural properties such as the small particle length, large pore size and the three-dimensional pore connectivity that permit the accessibility of p-NPP to the immobilized lipases during the reactions. Consequently, we concluded that TMPS materials are of the suitable mesoporous support for the enzymes. 相似文献