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41.
Ylures sans sel,evolution en phosphoranes et equilibre ylure ⇌ phosphorane : I Synthese et structure
Synthesis of new salt-free ylids , to , , , , and and phoiphoranes , , , , , to by addition of a trivalent phosphorus compound (phosphites and amino-phosphines ) to with dimethyl acetylencedicartboxylate in presence of a protic trapping reagent are described. The results are consistent with trapping of carbanionic species. In relation with the. cyclic of acyclic structure of the triivalent phosphorus compound and the protic trapping reagent ie : methanol, phenol, carboxylic acid, etc.., several pathways are involved. Clearly), three phenomena are shown : one can obtain an ylid via a phosphorane or conversely a phosphorane via an ylid or an equilibrium Phoiphorane ? ylid. Results are dealing with thermodynamic or kinetically controlled reactions. 相似文献
42.
C. H. Stam El Sayed El Ashry Yeldez El Kilany H. C. Van DerPlas 《Journal of heterocyclic chemistry》1980,17(3):617-619
X-ray crystallographic data show that the product obtained in the reaction of 4-(2-acetoxy-ethylidene)-4-hydroxy-2,3-dioxobutyro-1,4-lactone-2-(p-bromophenylhydrazone) with methyl-hydrazine is the bicyclic compound 2,6-dimethyl-3,4-dioxo-2,3,4,6,7,8-hexahydropyridazino-[4,3-c]pyridazine 4-(p-bromophenylhydrazone) ( 10 ) and not as originally suggested 1-methyl-3-(1-methylpyrazolin-3-yl)-4,5-pyrazoledione 4-(p-bromophenylhydrazone) ( 8 ). 相似文献
43.
Harry J. Whitlow Margaretha Andersson Mikael Hult Leif Persson Mohamed El Bouanani Mikael Östling Carina Zaring Nils Lundberg David D. Cohen Nick Dytlewski Peter N. Johnston Ian F. Bubb Scott R. Walker Erik Johanson Sture Hogmark P. Anders Ingemarsson 《Mikrochimica acta》1995,120(1-4):171-181
Recoil Spectrometry covers a group of techniques that are very similar to the well known Rutherford backscattering Spectrometry technique, but with the important difference that one measures the recoiling target atom rather than the projectile ion. This makes it possible to determine both the identity of the recoil and its depth of origin from its energy and velocity, using a suitable detector system. The incident ion is typically high-energy (30–100MeV)35C1,81Br or127I. Low concentrations of light elements such as C, O and N can be profiled in a heavy matrix such as Fe or GaAs. Here we present an overview of mass and energy dispersive recoil Spectrometry and illustrate its successful use in some typical applications. 相似文献
44.
Fractal analysis of hydroxyapatite from nitrogen isotherms 总被引:10,自引:0,他引:10
Samples of calcium hydroxyapatite, CaHap, were prepared via a wet method and subjected to thermal treatment in air in the temperature range 100-900 degrees C. Nitrogen adsorption-desorption isotherms were obtained on different samples, and their data points were used to analyze the fractal properties of the obtained solids. Both FHH and Neimark's equations were used for such purpose, and the agreement or disagreements between obtained results on using both equations are discussed. Considering the appropriate values of the obtained surface fractal dimensions D, it was concluded that an appreciable defractalization of the prepared hydroxyapatite is only noted upon calcinations at 900 degrees C. Below this temperature the loss in surface area and pore volume result from simultaneous bulk and surface mass transport, which conserve the initial surface roughness and average pore radius. Calcination at 900 degrees C caused sintering to proceed via bulk mass transport, with a consequent pore widening and a decrease in surface roughness. 相似文献
45.
Elías Molins Amílcar Labarta Javier Tejada Amparo Caubet Santiago Alvarez 《Transition Metal Chemistry》1983,8(6):377-380
Summary Magnetic moments and57Fe Mössbauer spectra at room temperature and at liquid nitrogen temperature of polynuclear ligand-bridged iron phthalocyanines, FePcL (L = pyrazine and 4,4-bipyridyl), are reported. The experimental data are in agreement with a pseudo-octahedral environment around the iron(II) cation. Partially oxidized derivatives, FePc(pz)I0.26 and FePc(bipy)I1.06 have been synthesized and their57Fe Mössbauer spectra and magnetic moments within the same temperature range obtained. Oxidation is shown to be metal centred and the iodine is found to be in I– form for FePc(pz)0.26 and as both I– and I
3
–
species for FePc(bipy)I1.06. While the magnetic moment of FePc(pz) increases upon oxidation, the opposite occurs for FePc(bipy). 相似文献
46.
2‐Amino‐4‐ethoxycarbonylpyridine 1 was used as a starting material in the synthesis of some 4‐substituted‐N1‐2‐pyridylsulfanilamide derivatives to evaluate their antimicrobial activity. The obtained compounds were of no particular effect against the tested organisms except for a noticeable inhibition of B. subtilis, which was of varying extents but remained clearly significant. 相似文献
47.
Novel synthesis of (1H)‐pyridin‐2‐one, pyrazolo[1,5‐a]pyrimidine and isoxazole derivatives incorporating N‐methylphthalimide moiety are reported. Reaction of enaminone 2 with malononitrile affords 4. Condensation of 2 with cyanothioacetamide or benzoylacetonitrile affords compounds 6 and 7 respectively. Reaction of 2 with hydrazine hydrate afford 2,3‐dihydrophthalazine‐1,4‐dione ( 10 ). Condensation of 2 with hydroxylamine and 3‐aminopyrazole derivatives affords compounds 12 and 15a,b respectively. Antimicrobial and antifungal activity were determined for representative compounds and most of them showed moderate activity as antimicrobial agents, while compounds 2 and 7 show strong activity against Aspergillus niger. The structure of the newly synthesized compounds was elucidated by elemental analyses and 1H nmr spectra and some cases by 13C nmr investigation. 相似文献
48.
Wagner-Czauderna Elżbieta Orlik Marek Zajączkowska Agnieszka Kalinowski Marek K. 《Transition Metal Chemistry》2004,29(3):276-279
Microsolvation of the [Ni(acac)(tmen)]+ complex by a series of aliphatic n-alcohols (Solv) has been studied in ClCH2CH2Cl solutions by spectrophotometry. Based on the changes in the electronic spectrum of the afore-mentioned complex, observed under the influence of any alcohol, the equilibrium constants for the formation of the [Ni(acac)(tmen)Solv]+ and [Ni(acac)(tmen)Solv2]+ species have been computed according to the algorithm presented in this work. It was found that, in all the systems studied, the stability of five-coordinated [Ni(acac)(tmen)Solv]+ is higher than that of octahedral [Ni(acac)(tmen)Solv2]+. The resulting values are discussed in terms of the Lewis basicity of alcohols. 相似文献
49.
J. Yves Laronze Rachida El Boukili Dominique Patigny Seloua Dridi Dominique Cartier Lean L vy 《Tetrahedron》1991,47(48):10003-10014
Upon acid catalyzed rearrangement after Sheradsky, the aryloximes A gave the tricyclic aminals C, which suffered hydrolysis to lactols E. The unique alcohol 29 was then prepared through a highly stereoselective equilibration-reductive alkylation of the epimeric mixture of lactols 22a,b. Two routes, one of which was stereospecific, allowed cyclization of 29 to (±)-aplysin 34. The yield was 2.5 % from oximes 2a,b. The isomeric epi-aplysin 35 and filiformin 36 were also obtained from 29. The debromo analogues 37,38 and 39 and their trideutero derivatives 41,42 and 43 were synthesized along similar line and allowed unequivocal structure elucidation by NMR spectroscopy. 相似文献
50.
ApparentpK a values of thymol blue solubilized in Aerosol-OT reversed micelles in carbon tetrachloride at 25 °C were determined spectrophotometrically. The effects of the Aerosol-OT concentration and the (water)/(surfactant)R ratio were investigated. The apparentpK a values increase as a function of increasing (R). All the measuredpK a values are less than that in water. The decrease ranges from 1.23 units (detergent=0.4 M,R=1.39) to 0.42 units (Aerosol-OT=0.6 M,R=9,25). These results are rationalized in terms of decreased hydronium ion activity in the micellar core due to its binding to the detergent SO3 ? groups. 相似文献