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131.
Addition of Reformatsky reagents (R1-CHZnBr-CO2R) to three β-aminoketones, yields mixtures of threo and erythro diastereomeric aminohydroxyesters. The relative configurations of the first members of each series (R1CH3), were determined by chemical correlation. Those of higher homologues (R1C2H5, iC3H7,tC4H9) are assigned by a study of their NMR spectra. 相似文献
132.
133.
134.
We derive microscopically precise identities for the geometry of small clusters in the equilibrium states of the two-dimensional Ising model with emphasis on near-critical phenomena. 相似文献
135.
Demethylation of methylthio imidazole 1 via a Pummerer rearrangement onto the corresponding sulfoxide 2 afforded imidazole thiol 4 which was then difluoromethylated with the sodium chlorodifluoroacetate/NaI system in 71% overall yield. 相似文献
136.
S. Raynal J.-P. Payan J.P. Marty C. Jacquot Elisabeth Lepain-Payan 《European Polymer Journal》1984,20(7):721-725
The chemical modification of poly(vinyl chloroformate) with sympathomimetics (phenyl ethylamine, ephedrine, p-hydroxyephedrine and p-hydroxymorephedrine) has been investigated. We have found convenient conditions to obtain soluble modified polymers with nearly quantitative substitution. The use of labelled compounds has shown that the rate and the yield of fixation on the polymer are independent of the nature of the amine. Kinetics in vitro of cleavage has shown that the rates of hydrolysis in stomacal, intestinal and enzymatic media are very low and similar; the observed variations seem to result from differences in solubility of the various modified polymers. 相似文献
137.
138.
R.H. Marty 《Topology and its Applications》1982,14(3):305-311
Let X denote the product of m-many second countable Hausdorff spaces. Main theorems: (1) If S?X is invariant under compositions, m is weakly accessible (resp., nonmeasurable), and F?S is sequentially closed and a sequential Gσ-set which is invariant under projections for finite sets (resp., F?S is sequentially open and sequentially closed), then F is closed. (2) If S?X is invariant under projections and m is nonmeasurable, then every sequentially continuous {0, 1} valued function on S is continuous. (3) A sequentially continuous {0, 1}-valued function on an m-adic space of nonmeasurable weight is continuous. Now let X denote the product of arbitrarily many W-spaces and S?X be invariant under compositions. (4) Then in S, the closure of any Q-open subset coincides with its sequential closure. 相似文献
139.
140.
Using a recently proposed non-empirical Heisenberg hamiltonian, the ground and excited covalent surfaces of the styrene molecule are calculated as functions of the external double-bond twisting angle θ, including full bond-length optimisation. The lowest excited singlet surface exhibits a barrier at 0 ?~ 45° resulting from a weakly avoided crossing of two neutral diabatic surfaces. The isomerisation should proceed from the twisted funnel. This model and the calculated transition energies are in good agreement with experiment. 相似文献