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991.
Guoyi Bai Chenfang Zhang Yuecheng Zhang Haijun Yu Fei He Huisen Ning Ligong Chen 《Reaction Kinetics and Catalysis Letters》2007,90(2):373-380
The racemization of R-(-)-2-amino-1-butanol in a reaction using Co/γ-Al2O3 catalysts and catalysts modified by Mg or Ca was investigated in this paper. Complete racemization was achieved with a yield
of over 83% at using the Mg modified Co/γ-Al2O3 catalyst under optimized reaction conditions of 170°C and 2.5 MPa of H2. The catalysts were thoroughly characterized by XRD, XPS, TPR, SEM and TEM. The addition of Mg and Ca may be advantageous
for dispersing and stabilizing the active species of the Co/γ-Al2O3 catalyst, protecting from sintering, significantly improving its catalytic activity and stability. 相似文献
992.
5-Alkyl(aryl)-3-arylidene-3H-pyrrolin-2-ones were synthesized by ammonolysis of their O-heteroanalogs or by the reactions of 5-alkyl(aryl)-3H-pyrrolin-2-ones with aromatic aldehydes. The structures of the compounds obtained were confirmed by 1H NMR spectra. 相似文献
993.
Tushar S. Basu Baul Keisham Surjit Singh Michal Hol?apek 《Journal of organometallic chemistry》2005,690(6):1581-1587
The complex, [(PhCH2)2{O2CC6H4{N(H)N(C6H3-4(O)-5-O)}-o}Sn]2 (1), is obtained as the exclusive reaction product from the reaction of sodium 2-[(E)-2-(3-formyl-4-hydroxyphenyl)-1-diazenyl]benzoate and (PhCH2)3SnCl. The reaction possibly proceeds via Dakin type rearrangements where arylazosalicylaldehyde is oxidized to arylazocatechol, followed by facile Sn-C bond cleavage. Complete assignments were achieved by 1H, 13C, 2D 1H-119Sn HMQC (119Sn chemical shift), 1D gs 1H-15N HMQC (1J(15N, 1H) coupling constant) NMR and ESI-MS. The crystal structure of compound 1 as determined by X-ray diffraction analyses shows a cyclic centrosymmetric dinuclear moiety linked into extended chains by pairs of long Sn?O contacts of approximately 3.2 Å. Two polymorphs were identified and their structures differ primarily in the packing arrangement afforded by the benzyl groups. In one polymorph, when viewed along the Sn?Sn vector, the benzyl groups at each Sn-atom are oriented to form an S-shape, while they form a U-shape in the second polymorph. 相似文献
994.
The surface pressure-molecular area curve of the mixed monolayer of 16-(9-anthroyloxy) palmitic acid (16AP) and fatty acid (palmitic or stearic acids) showed various kink points which indicated the phase transitions of the monolayer. On the basis of the surface phase rule, the phase diagrams of the mixed monolayer were elucidated. The bifunctional molecule, 16AP, takes two orientations in a monolayer state, that is, horizontal and vertical ones. Horizontally oriented 16AP and vertically oriented fatty acid form a mixed monolayer but this exhibits deviation from the ideal mixing, which was interpreted in terms of the surface regular solution theory. On the other hand, the 16AP molecule in the vertical state was found to be immiscible with the fatty acid molecule in a monolayer de spite both molecules being vertical to the surface and parallel to each other. This was caused by the participation of the 9-anthroyloxy moiety of 16AP in the interaction of 16AP and fatty acid in the hydrophobic region of the monolayer. 相似文献
995.
Reactions of Tetraphosphorus Trichalcogenides with Alkyl Iodides Reactions of alkyl iodides RI (R = CHI2, CH2I or tert-Butyl) with P4E3 (E = S or Se) under the influence of light resulted in cleavage of the basal P3 ring. β-P4E3(I)R was formed initially, then it rearranged to the more stable α-P4E3(I)R structure. 31P NMR data of these products were measured and discussed, along with 77Se data for α- and β-P477SeSe2(I)CHI2. On reaction of P4S3 with tert-butyl iodide in CS2 or with sec-butyl iodide or iso-propyl iodide in dioxane, the new type of compounds P5S2R was observed. In this a sulfur bridge of P4S3 is replaced by a P? R group. 31P-NMR data for these compounds are reported. 相似文献
996.
Ali Taha Viktor Gutmann Wolfgang Linert 《Monatshefte für Chemie / Chemical Monthly》1991,122(5):327-339
Summary The solvatochromic and thermochromic behaviour of a series of mixed Ni(II) complexes with unsubstituted and substituted -diketones and diamines in the solvents 1,2-dichloroethane (DCE), acetonitrile (An), acetone (AC),n-butanol (n-BuOH), formamide (FA), N,N-dimethylformamide (DMF), dimethylsulfoxide (DMSO) and pyridine (PY) has been studied and characterized on the basis of electronic spectra. Spectrophotometric methods have been used to evaluate equilibrium constants and their enthalpic and entropic terms for the formation of Ni(-dik)(diam)L
+ and Ni(-dik)(diam)L
2
+
. Increasing donor strength of the donor-solvents (L) and (or) increasing electronwithdrawing parameters of the substituents at the -diketone and the diamine ligands lead to increasing formation constants, paralleled by relative increase in the stability of the five-coordinated species Ni(-dik)(diam)L
+. The results are discussed in terms of the extended donor-acceptor concept.On leave of absence from the Faculty of Education, Ain Schams University, Roxy, Cairo, Egypt 相似文献
997.
Jean Diebolt 《Journal of Theoretical Probability》1991,4(4):655-667
We consider the Markov chainX
n+1=T(X
n
)+
n
, where {
n
;n1} is a
d
-valued random sequence of independent identically distributed random variables, and the functionT:
d
d
is measurable and satisfies a suitable growth condition. Under certain conditions involvingT and the probability distribution of
n
, we show that this Markov chain is ergodic. Moreover, we obtain sharp upper bounds for the tail of the corresponding stationary probability density function. In our proofs, we make use of the Leray-Schauder fixed-point theorem. 相似文献
998.
Hideki Takayasu Misako Takayasu Astero Provata Greg Huber 《Journal of statistical physics》1991,65(3-4):725-745
We study a generalized aggregation process in which charged particles diffuse and coalesce randomly on a lattice. For one-dimensional and mean-field models, we show that there exists a statistically-invariant steady state when randomly charged particles are continuously injected. The steady-state charge distribution obeys a power law with the exponent depending both on the type of the injection and on the spatial dimension. The response of the system to a perturbation (i.e., relaxation) is characterized by either a power law decay (t
–
,1) or a compressed exponential decay [exp(–t
),>1]. 相似文献
999.
This study applies the theory of stochastic processes to the equilibrium statistical physics of polymers in solution. The topics treated include random copolymers and randomly branching polymers, with self-consistent mean field effects. A new and more natural way of dealing with Boltzmann weighting is discussed, which makes it possible from the beginning of a calculation to consider only the physical polymer conformations. We also show that in general the random copolymer problem can be reduced to the ordinary polymer problem, and treat the self-consistent field problem for a general branching polymer. 相似文献
1000.
Bromination of -aminovinyl ketones (AVK) with geminal arrangement of the fluoroalkyl and amino groups gives N-bromo derivatives. Regioisomeric AVK with the amino groups in the -position relative to the fluoroalkyl group undergo bromination under analogous conditions to give a mixture of the -bromo and ,N-dibromo derivatives. -Bromo derivatives of AVK disproportionate upon storage.Division of Fine Chemical Synthesis, Institute of Organic Chemistry, Urals Branch, Russian Academy of Sciences, 620219 Ekaterinburg. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 3, pp. 746–749, March, 1992. 相似文献