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91.
Photo-extrusion of nitrogen from the azoalkane 1 in the presence of molecular oxygen gave besides the hydrocarbons 3 and 5, the endoperoxide 10 and hydroperoxide 11, the former via trapping of the 1,4-diradical 4 by triplet oxygen, the latter by ene-reaction-6f hydrocarbon 5 with singlet oxygen. 相似文献
92.
S.I. Pombrik D.N. Kravtsov B.A. Kvasov E.I. Fedin 《Journal of organometallic chemistry》1977,136(2):185-200
A 19F NMR study of the transmission of electronic effects has been made for the systems Ar2EC6H4F-4 (E = Sb, Bi, CH, N). The fluorine chemical shifts obtained are correlated with the polar constants (Σσo and Σσ) of the substituents, suggesting that electronic effects are transmitted through the SbCar, BiCar and CCar bonds predominantly by an inductive mechanism, whereas the transmission through the NCar bonds is contributed to significantly by classical resonance effects due to competitive conjugation of the lone pair with the aromatic rings, and the substituents therein. A dual parameter correlation of the fluorine chemical shifts with the inductive (σI) and resonance (σoR and σR) parameters of the substituents in the aromatic rings has led to similar conclusions. The inductive transmission through the bridging Sb and Bi atoms has been assigned to the absence of conjugation of lone pair and vacant d-orbitals of the metals with π-electron systems of the aromatic rings. On the basis of the values of the ? coefficients for the correlation equations obtained it has been established that the transmitting ability of the BiCar bonds is close to that of the CalCar bonds and considerably lower than the transmitting ability of the NCar bonds. 相似文献
93.
William H. McCarroll Cynthia Darling Gary Jakubicki 《Journal of solid state chemistry》1983,48(2):189-195
Fused salt electrolysis has been used to prepare a number of reduced oxides of molybdenum with lanthanum, neodymium, and yttrium in single crystal or oriented polycrystalline form. The average valence of molybdenum in the various compounds ranged from 5.67 to 3.50. Previously unreported compounds include La5Mo4O16 (triclinica = 5.64 Å,b = 20.7 0Å,c = 5.64 Å, α = 86.55°, β = 90.0°, γ = 93.45°); La2Mo2O7 (orthorhombic,a = 12.19 Å,b = 6.05 Å,c = 3.87 Å); LaMo2O5 (hexagonal,a = 8.378 Å,c = 19.26 Å). In addition, single crystal specimens have been prepared of Y2MoO5,Ln5Mo3O16(Ln =La, Nd) and metal atom cluster compounds of theA2Mo3O8 type (A = Mg, Co, Ni, Zn). 相似文献
94.
Roger N. F. Thorneley 《Journal of organometallic chemistry》1974,70(3):C37-C39
The kinetic isotope effect for β-hydride elimination from alkyliridium(I) complexes has bee found to be kH/kD = 2.28 ± 0.20. 相似文献
95.
A type of novel hybrid hydrogels from sodium humate (SH), polyacrylamide (PAM), and hydrophilic Laponite clay were prepared using potassium persulfate (KPS) as the initiator and N,N′-methylenebisacrylamide (MBA) as the cross-linker. The structures of the hydrogels were characterized by field emission scanning electron microscope and FTIR. Their swelling properties, swelling mechanism and rheological properties were also investigated. Experiments show that the composite is heterogeneous in the PAM/SH hydrogel system, while the clay collaborates with SH and improves the network structure of PAM/SH/clay hydrogel. High water-absorbing capability is shown for both hydrogel systems. Han plot proves that clay and SH are compatible with PAM for PAM/SH/clay hydrogels. 相似文献
96.
G. Bruno P. Capezzuto G. Cicala F. Cramarossa 《Plasma Chemistry and Plasma Processing》1986,6(2):109-125
Plasma-chemical reduction of SiCl4 in mixtures with H2 and Ar has been studied by optical emission spectroscopy (OES) and laser interferometry techniques. It has been found that the Ar:H2 ratio strongly affects the plasma composition as well as the deposition (r
D) and etch (r
E) rates of Si: H, Cl films and that the electron impact dissociation is the most important channel for the production of SiClx species, which are the precursors of the film growth. Chemisorption of SiClx and the reactive surface reaction SiClx+H–SiCl(x–1)0+HCl are important steps in the deposition process. The suggested deposition model givesr
D [SiClx][H], in agreement with the experimental data. Etching of Si: H, Cl films occurs at high Ar: H2 ratio when Cl atoms in the gas phase become appreciable and increases with increasing Cl concentration. The etch rate is controlled by the Cl atom chemisorption step. 相似文献
97.
The Reaction of SeCl4 with Transition Metal Tetrachlorides. Synthesis and Crystal Structures of (SeCl3)2MCl6 with M = Zr, Hf, Mo, Re The transition metal tetrachlorides ZrCl4, HfCl4 and MoCl4 react with SeCl4 in closed ampoules at temperatures of 140°C to (SeCl3)2MCl6 (M = Zr, Hf, Mo) which are all isotypic and crystallize in the (SeCl3)2ReCl6 structure type (orthorhombic, Fdd2, Z = 8, lattice constants for M = Zr: a = 1165.7(1)pm, b = 1287.2(2)pm, c = 2180.2(2)pm; for M = Hf: a = 1162.9(2)pm, b = 1285.0(2)pm, c = 2178.2(3)pm; for M = Mo: a = 1153.8(1)pm, b = 1267.7(1)pm, c = 2147.4(2)pm). The Cl? ions form a hexagonal closest packing with one fourth of the octahedral holes filled by Se4+ and M4+ in an ordered way. The MCl6 octahedra are regular, the SeCl6 octahedra are distorted with 3 short and 3 long Se? Cl bonds (mean 215 pm and 287 pm). The structures can thus be regarded as built of SeCl3+ and MCl62? ions. Magnetic susceptibility measurements show for M = Zr the expected diamagnetic behavior, for M = Mo and Re paramagnetic behavior according to the Curie-Weiss law with magnetic moments of 2.5 B. M. for M = Mo and 3.7 B. M. for M = Re corresponding to 2 and 3 unpaired electrons respectivly. 相似文献
98.
Luo J Zheng QY Chen CF Huang ZT 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(20):5917-5928
A series of inherently chiral calix[4]arenes with cone and partial cone conformations and with crown ether moieties of variable size have been readily synthesized. By taking advantage of the carboxy appendage on the lower rim, these were condensed with the chiral auxiliary (S)-BINOL to form diastereomers which, in most cases, could be separated by preparative TLC, or more desirably, by column chromatography on silica gel (diastereomeric excess >99 % based on HPLC analysis). Seven enantiopure antipodes of inherently chiral calix[4]crowns were obtained after hydrolysis. It has been found that both the size of the crown moiety and alkylation of the last phenolic hydroxy group (accompanied with or without a change in the conformation) affect the separation of the diastereomers. 相似文献
99.
Oxygen reduction on immersed gold electrodes has been studied in Li2CO3 melt under steady-state conditions and by the potential-sweep method. Reaction order measurements have established that the species being reduced is not molecular oxygen, but the peroxide ion. The latter is in chemical equilibrium with molecular oxygen and oxide ions. The rate-determining step is the primary charge transfer where (O?) is a transient species. The exchange current densities and activation energies have been determined. Under conditions where O22? diffusion is not limiting (e.g. meniscus electrodes) the rate of neutralization of oxide by CO2 at the electrode surface is probably rate-determining. 相似文献
100.
The program MINIPOL, designed to run on a desk-computer with 32 kbytes of memory, can calculate the optimum values of overall protonation constants and molar intensities of up to 8 species with composition HXXXLρ, from differential-pulse polarographic data. 相似文献