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Núbia Boechat M?nica M. Bastos Lindalva C. Maciel Warner B. Kover Solange M. S. V. Wardell James L. Wardell 《Journal of chemical crystallography》2011,41(6):874-879
Abstract
The compounds, N-{2-[(5-amino-1,3,4-thiadiazol-2-yl)difluoromethyl]-4-chlorophenyl}acetamide (1: X = Cl) and N-{2([(5-amino-1,3,4-thiadiazol-2-yl)difluoromethyl]-4-bromo-phenyl}acetamide (1: X = Br), are isostructural. The molecules are near ‘‘V’’ shaped with the angles between the two aromatic planes ca. 84° in each case. The various intermolecular interactions, namely N–H···O, N–H···N, N–H···F, and C–H···N hydrogen bonds and C–H···π, C–Cl···π and C–O···π interactions, generate 3-D arrays. Compound (1: X = Cl) crystallizes in the monoclinic space group P21/c with a = 16.9032(7) ?, 10.2193(4) ?, c = 7.5227(4) ?, β = 100.179(3)° and Z = 4. Compound (1: X = Br) crystallizes in the monoclinic space group P21/c with a = 17.2119(4) ?, 10.2167(2) ?, c = 7.5677(2) ?, β = 100.326(2)° and Z = 4. 相似文献2.
Franco M Rosenbach N Ferreira GB Guerra AC Kover WB Turci CC Mota CJ 《Journal of the American Chemical Society》2008,130(5):1592-1600
Rearrangement and nucleophilic substitution of cyclopropylcarbinyl bromide over NaY and NaY impregnated with NaCl was observed at room temperature. The first-order kinetics are consistent with ionization to the bicyclobutonium cation, followed by internal return of the bromide anion or nucleophilic attack by impregnated NaCl to form cyclopropylcarbinyl, cyclobutyl, and allylcarbinyl chlorides. The product distribution analysis revealed that neither a purely kinetic distribution, similar to what is found in solution, nor the thermodynamic ratio, which favors the allylcarbinyl halide, was observed. Calculations showed that bicyclobutonium and cyclopropylcarbinyl carbocations are minimal over the zeolite structure, and stabilized by hydrogen bonding with the framework structure. A new process of nucleophilic substitution is reported, namely halogen switch, involving alkyl chlorides and bromides of different structures. The reaction occurs inside the zeolite pores, due to the confinement effects and is an additional proof of carbocation formation on zeolites. The results support the idea that zeolites act as solid solvents, permitting ionization and solvation of ionic species. 相似文献
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Summary. In this work, new interpolation error estimates have been derived for some well-known interpolators in the quasi-norms. The estimates are found to be essential to obtain the optimal a priori error bounds under the weakened regularity conditions for the piecewise linear finite element approximation of a class of degenerate equations. In particular, by using these estimates, we can close the existing gap between the regularity required for deriving the optimal error bounds and the regularity achievable for the smooth data for the 2-d and 3-d p-Laplacian.Mathematics Subject Classification (1991): 65N30 相似文献
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Energy spectra of electrons ejected from an Ar target, in the forward direction, by a low energy positron beam have been measured
and compared with theory. Structures are present in these spectra at energies compatible with electron capture to continuum
states of the scattered positron (ECC) and with binary collisions. 相似文献
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Cowern NE Zalm PC van der Sluis P Gravesteijn DJ de Boer WB 《Physical review letters》1994,72(16):2585-2588
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Moônica M. Bastos Lúcia M. U. Mayer Elza C. S. Figueira Marcio Soares Núbia Boechat Warner B. Kover 《Journal of heterocyclic chemistry》2008,45(4):969-973
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Described is the synthesis of the four optically pure epoxy-tosylates 5, 6, 9 and 12, each with four chiral centers determined, from a single starting material, (R)(-) carvone. 相似文献
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Details and methodological comparisons are presented on the preparation of a norbisabolide γ-lactone analogue (4) via dichloroketene cycloaddition to limonene followed by regioselective Baeyer-Villiger oxidation (CH3CO3H) of the α,α-dichlorocyclobutanones 3 and C-Cl reduction (Zn/HOAc). The sequence of reduction followed by oxidation (HOCI) applied to 3 produced 4 in much better yield. 相似文献
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