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151.
Sameena Ashraf Keith D. Bartle Anthony A. Clifford Robert Moulder 《Journal of separation science》1992,15(8):535-538
Lubricating oil additives have been analyzed by supercritical fluid chromatography on open tubular and packed capillary columns. Carbon dioxide and modified carbon dioxide were used as mobile phases and detection was accomplished by flame ionization and micro UV. Rapid and efficient analysis of the lubricating oil additives was demonstrated. 相似文献
152.
Jörg Senn-Bilfinger John R. Ferguson Keith W. Lumbard Karl Zech Peter J. Zimmermann 《Tetrahedron letters》2006,47(19):3321-3323
Glucuronide conjugates of Soraprazan (BY359), a potent novel anti-secretory drug (currently in Phase II clinical trials), were not directly accessible synthetically. This was due to the relative instability of Soraprazan under the harsh Lewis acid conditions employed in popular glucuronidation methodologies and a lack of reactivity under alternative, Koenigs-Knorr, coupling conditions. We have now devised a successful synthesis using the novel N-acetylated Soraprazan to access the required glucuronide metabolites on gram scale. Coupling of this novel aglycone with methyl 1-O-trichloroacetimidoyl-2,3,5-tri-O-isobutyryl-α-d-glucopyran-uronate in the presence of trimethylsilyl trifluoromethanesulfonate (TMSOTf) gave the protected glucuronide intermediates. A one-pot two-step deprotection involving hydrolysis of the ester functionalities and removal of the N-acetyl group with alkaline hydrazine delivered the title compounds in satisfactory yield. 相似文献
153.
Shigeru?ArimotoEmail author Mark?Spivakovsky Keith?F.?Taylor Paul?G.?Mezey 《Journal of mathematical chemistry》2005,37(2):171-189
The present article is a direct continuation of the first part of this series. We reduce a proof of the Fukui conjecture (concerning the additivity problem of the zero-point vibrational energies of hydrocarbons) to that of a proposition related to the theory of algebraic curves, so that we can focus on the key mechanism of the additivity phenomena. Namely, by establishing what is called the Basic Piecewise Monotone Theorem (BPMT), we reduce a proof of the Fukui conjecture to that of a proposition, called the Local Analyticity Proposition, Version 1 (LAP1), which admits a proof via resolution of singularities. By LAP1, the essential part of the mechanism of the asymptotic linearity phenomena is extracted and is elucidated by using tools from the mathematical theory of algebraic curves, whose language is of vital importance in analyzing the crux of the additivity mechanism.
Dedicated to the memory of Prof. Kenichi Fukui (1918–1998). 相似文献
154.
Ibrahim Y Alsharaeh E Dias K Meot-Ner Mautner M El-Shall MS 《Journal of the American Chemical Society》2004,126(40):12766-12767
We studied the stepwise hydration and solvent-mediated deprotonation of the benzene*+ cation (Bz*+) and found several unusual features. The solvent binding energies DeltaH on-1,n for the reactions Bz*+(H2O)n-1 + H2O --> Bz*+(H2O)n are nearly constant at 9 +/- 1 kcal mol-1 for n = 1 to 8. We observed a remarkable sudden decrease in the entropy of association accompanying the formation of Bz*+(H2O)7 and Bz*+(H2O)8, indicating strong orientational restraint in the hydration shells of these clusters consistent with the formation of cagelike structures. We observed the size-dependent deprotonation of Bz*+ in a cooperative multibody process, where n H2O molecules (n >/= 4) can remove a proton from Bz*+ to form protonated water clusters. We measured, for the first time, the temperature dependence of such a process and found a negative temperature coefficient of a magnitude unprecedented in any chemical reaction, of the form k = AT-67+/- 4, or in an Arrhenius form having an activation energy of -34 +/- 1 kcal mol-1. The temperature effect may be explained by Bz*+ and four H2O molecules needing to be assembled from gas-phase components to form the reactive species. Such large temperature effects may be therefore general in solvent cluster-mediated reactions. 相似文献
155.
Modifications of the SCF-LCAO-π-MO method analysed in the previous paper are described in which provision is made for the incorporation of Variable Bond Order and Variable Electronegativity procedures. A comparison is made with the results of other π-electron calculations and values are reported for twenty hydrocarbon systems. 相似文献
156.
Condensation of o-phenylenediamine with 2-, 3- and 4-nitronaphthalene-1,8-dicarboxylic anhydrides gives, in each case, an isomer mixture. Separation of the mixtures into the six isomeric mononitro-7H-benzimidazo[2,1-a]benz[de]isoquinolin-7-ones is described and the isomers characterised in respect of previously reported data on some isomers; ir and mass spectrum data are reported, the latter showing fragmentation ions which may be used in characterising dyes based on this chromophore. Other new derivatives of 7H-benzimidazo[2,1-a]benz[de]isoquinolin-7-one are also described. 相似文献
157.
John M. Adams Keith Martin Richard W. McCabe 《Journal of inclusion phenomena and macrocyclic chemistry》1987,5(6):663-674
Suitably modified smectite clays can be very selective catalysts for a wide range of organic reactions. While it has long been known that such materials can act as Bronsted and Lewis acids, it has been shown recently that they are also effective Diels-Alder catalysts. A selection of illustrative reactions is given which emphasises their wide range of use, their selectivity, and the ease of work-up after reaction. In each case, mechanistic information is presented, e.g., on the site of reaction (whether interlayer or surface), rate determining steps, etc. The regiochemical consequences of the restricted reaction space are stressed.Based on material presented at the Fourth International Symposium on Inclusion Phenomena and the Third International Symposium on Cyclodextrins, Lancaster, U.K., 20–25 July 1986. 相似文献
158.
A family of of open subsets of the real line is called an ω-cover of a set X iff every finite subset of X is contained in an element of . A set of reals X is a γ-set iff for every ω-cover of X there exists such that In this paper we show that assuming Martin's axiom there is a γ-set X of cardinality the continuum. 相似文献
159.
Keith A. Hunter Margaret R. Leonard Peter D. Carpenter J. David Smith 《Colloids and surfaces. A, Physicochemical and engineering aspects》1997,120(1-3):111-121
The kinetics of iron colloid aggregation in estuaries have been simulated with a model estuary in which seawater is continuously pumped into a reservoir initially containing river water. Profiles of colloidal Fe concentration versus salinity produced in this apparatus closely resembled field data for actual estuaries. Synthetic Fe colloids prepared by peptising Fe(OH)3 with humic acid and phosphate showed very similar kinetic behaviour. Aggregation rate was found to be almost independent of velocity shear rate, implying that most aggregations are induced by brownian interparticle collisions. A heterogeneous kinetic model is proposed to explain the kinetic behaviour of Fe colloids during seawater-induced aggregation. This model describes kinetic behaviour in terms of a log-normal distribution of rate constants characterised by a mean value k and a standard deviation γ. Experiments showed that k is linearly related to the rate constant for salinity increase during mixing. This coupling of salinity changes and aggregation rate leads to Fe-salinity profiles that are nearly independent of the rate of salinity change, but which are dependent on γ. 相似文献
160.
W. Clark Still Lawrence J. Macpherson Toshiro Harada James F. Callahan Arnold L. Rheingold 《Tetrahedron》1984,40(12):2275-2281
The conformations of macrocyclic intermediates provide a useful medium through which distant chiral centers may control chemical reactions. In this paper, we show that macrocycles made by cyclization of simple acyclic starting materials with an auxiliary spacer may be used to prepare stereochemically complex acyclic products. 相似文献