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141.
近年来,分子内环加成反应已广泛用于甾体化合物全合成,其主要一步是由取代的苯并环丁烯热裂而成的5,6-二亚甲基-1,3-环己二烯发生区域专一和立体选择性的环加成反应,构成甾体骨架。现在用此法已合成了一系列消旋和光学活性的甾体化合物。 相似文献
142.
Cruz A. J. G. Araujo M. L. G. C. Giordano R. C. Hokka C. O. 《Applied biochemistry and biotechnology》1998,(1):579-592
Cephalosporin C production process withCephalosporium acremonium ATCC 48272 in synthetic medium was investigated and the experimental results allowed the development of a mathematical model
describing the process behavior. The model was able to explain fairly well the diauxic phenomenon, higher growth rate during
the glucose-consumption phase, and the production occurring only in the sucrose-consumption phase.
Moreover, the process was simulated utilizing the neural-networks technique. Two feed-forward neural-networks with one hidden
layer were employed. Both models, phenomenological and neural-networks based, satisfactorily describe the bioprocess. The
difficulties in determining kinetic parameters are avoided when neural networks are utilized. 相似文献
143.
Teleshev A. T. Vasil"eva L. N. Nifant"ev E. E. Tsodikov M. V. Bukhtenko O. V. Zhdanova T. N. 《Russian Chemical Bulletin》2003,52(9):2083-2085
The reactivities of cyclophosphite precursors in alkoxo syntheses involving titanium(iv) tetra(n-butoxide) were studied by 31P NMR and IR spectroscopy. 2-Diethylamido-4-methyl-1,3,2-dioxaphosphinane and 4-ethyl-2,6,7-trioxaphosphabicyclo[2.2.2]octane in benzene are inert toward Ti(OBu)4. Gelation is accompanied by hydrolysis 2-diethylamido-4-methyl-1,3,2-dioxaphosphinane to give the corresponding hydrophosphoryl compound, while 4-ethyl-2,6,7-trioxaphosphabicyclo[2.2.2]octane remains intact during gelation. 相似文献
144.
D. N. Dybtsev M. P. Yutkin E. V. Peresypkina A. V. Virovets Y. Hasegawa H. Nishihara V. P. Fedin 《Russian Chemical Bulletin》2007,56(9):1782-1786
The reaction of Co(NO3)2·6H2O with 1,3,5-benzenetricarboxylic acid (H3btc, trimesic acid) in DMF at 100 °C afforded the coordination polymer [Co3(dmf)6(btc)(Hbtc)(H2btc)]··9H2O (1) (dmf is N,N′-dimethylformamide, DMF). According to the X-ray diffraction study, the metal-organic coordination polymer is composed of
planar honeycomb (6,3) networks, in which the organic benzenetricarboxylate anions and the inorganic Co2+ cations play a role of three-connected nodes. Disordered water molecules are intercalated between the layers. A study of
the magnetic properties showed the presence of a weak antiferromagnetic coupling between the Co2+ ions (S = 3/2).
Dedicated to Academician G. A. Abakumov on the occasion of his 70th birthday.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1719–1723, September, 2007. 相似文献
145.
在SmI3作用下和中性室温的条件下, 环戊酮能与醛缩合, 得到几乎定量产率的α, α'-二亚苄基环戊酮; 但对环己酮, 产率仅在20%左右。 相似文献
146.
L. F. Kosyanchuk N. V. Kozak O. I. Antonenko G. Ya. Menzheres Yu. S. Lipatov 《Theoretical and Experimental Chemistry》2006,42(6):357-363
For semi-interpenetrating polymer networks (semi-IPNs) based on an incompatible polyurethane network/linear polymethylmethacrylate
pair formed in situ in the presence of 3d metal chelates, we have studied the effect of the system composition on the kinetics
of formation of the components and the nature of complex formation between the metal compound and the polymer matrix. The
ratio of the system components has been shown to have an effect on the selection of the macroligand in formation of complexes
of the metal chelate with the polar groups of the semi-IPN, where the general character of the kinetic behavior for the formation
of the network and the linear polymer is preserved.
__________
Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 42, No. 6, pp. 351–356, November–December, 2006. 相似文献
147.
A series of P[N-isopropylacrylamide (NIPAM)] latexes with different contents of cyano groups were successfully prepared by either seeded
or shot-growth polymerizations of an aqueous solution containing acrylonitrile (AN) onto a seed P[NIPAM] latex, respectively, and further characterized by FT-IR, 1H-NMR, elemental analysis, as well as by quasielastic light scattering (QELS) and scanning electron microscopy (SEM). All
prepared surface-cyanofunctionalized P[NIPAM] latexes exhibited the same range of lower critical solution temperature (LCST) as a pure P[NIPAM] latex. The shot polymerization process proved more efficient at yielding cyano derivatized latexes than the seeded
polymerization technique. The amount of incorporated cyano groups onto the particles was determined with a good correlation
both by 1H-NMR and elemental analysis. The higher the amount of initially introduced AN monomer in the reaction mixture, the more cyano
groups were incorporated onto the particles. The surface of the particles with high content of cyano groups appeared quite
rough by SEM in comparison with that of the pure P[NIPAM] particles.
Received: 25 February 1998 Accepted: 23 June 1998 相似文献
148.
149.
Marina A Zhuravleva 《Journal of solid state chemistry》2003,173(2):280-292
The RE3Ga9Ge compounds (RE=Y, Ce, Sm, Gd and Yb) were synthesized at 850°C in quantitative yield from reactions containing excess liquid Ga. The orthorhombic crystal structure is characterized by a unique three-dimensional open Ga framework with parallel straight tunnels. In the tunnels, inserted are arrays of the RE atoms together with interpenetrated monoatomic RE-Ga-Ge planes. A complex disordered arrangement of the RE and Ga atoms is observed in the monoatomic plane. Depending on the extent of disorder, the crystal structure could be presented either in a sub-cell (no ordering) or in a super-cell (partial ordering). Single-crystal X-ray data for Ce3Ga9Ge sub-structure: space group Immm, Z=2, cell parameters a=4.3400(12) Å; b=10.836(3) Å; and c=11.545(3) Å; super-structure: space group Cmma, Z=8, cell parameters a=8.680(3) Å; b=23.090(7) Å; and c=10.836(3) Å. The refinement based on the full-matrix least squares on Fo2[I>2σ(I)] converged to final residuals R1/wR2=0.0226/0.0528 and 0.0729/0.1569 for the sub- and super-structures, respectively. The relationship between the disordered sub-structure and partially ordered super-structure is discussed. Magnetic susceptibility measurements show Curie-Weiss behavior at the temperatures above 30 K with the negative Weiss constants Θ=−49(1) and−7.7 K for Gd and Ce analogs, respectively. An antiferromagnetic transition is observed in the Gd analog at TN=26.1 K. The μeff obtained for both analogs is close to the RE3+ free-ion value. 相似文献
150.
用自旋-晶格弛豫时间(T1)研究了溶胀的交联聚丙烯酰胺-丙烯酸网络和线型聚苯乙烯溶液中质子的弛豫行为。交联网络中,随着交联度增大,T1CH/T1CH2的值由1.17逐渐趋近于1;而线型聚苯乙烯溶液中,T1CH/T1CH2的值由最稀浓度下的1.7过渡到1。说明在交联网络中,交联度很低时,链段的运动已经相当受约束;但交联度很大时,充分溶胀的交联网络中链段运动仍有一定自由度。而在线型高分子浓溶液中,链段的运动严重受阻,导致自旋扩散效应非常完全,彻底平均掉了各质子间T1时间的差异。 相似文献