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41.
42.
Giorgio Abbiati Alessandro Cirrincione de CarvalhoElisabetta Rossi 《Tetrahedron》2003,59(37):7397-7402
The cycloaddition reactions of 1-p-tolyl and 1-benzyl- 2,4-diphenyl-1,3-diazabuta-1,3-dienes with a variety of aryl and alkyl isocyanate and isothiocyanate are described. The reaction mechanism is also discussed. 相似文献
43.
Prabir Kumar Pal Dipa Nandi Ajit Kumar Chaudhuri 《Journal of polymer science. Part A, Polymer chemistry》1989,27(5):1687-1699
The polymerization of methyl methacrylate initiated by cupric laurate in combination with benzoin has been investigated in carbon tetrachloride medium at 60°C. The rate of polymerization was found to be proportional to the square root of both cupric ion and benzoin concentrations, and to the 1.5th power of the monomer concentration. Spectral studies indicated that there is a complex formation between cupric ion and the monomer methyl methacrylate. A reaction scheme, based on initial formation of the complex and its subsequent reaction with benzoin to produce the free radicals responsible for initiation has been postulated to explain the observed results. 相似文献
44.
Complexes of CuHg(NCS)4, CuHg(NCS)2 (NCSe)2 and CuHg(NCSe)4 with tetrahydrofuran, dioxane, pyridine, 2-aminopyridine, nicotinamide, bipyridine and phenanthroline have been prepared and comparative studies made. Bipyridine and phenanthroline form cationic—anionic [CuL3]2+ [Hg(SCN)4]2? (L = bipy, phen) complexes with CuHg(NCS)4 and dinuclear bridged complexes with CuHg(NCSe)4 and CuHg(NCS)2 (NCSe)2. For other ligands the nature of the complexes is binuclear or polynuclear. The comparative stability of the -XCN- bridge (X = S, Se) is CuHg(NCSe)4 > CuHg(NCS)2 (NCSe)2 > CuHg(NCS)4. 相似文献
45.
Summary A study has been made of the separation of alkali and alkaline earth metals. With mixtures of solvents, such as ethyl cellosolve, water and hydrochloric acid and acetone, water and hydrochloric acid in the ratio of 702010 and at different temperatures, a complete separation of alkaline earth metals was effected. Of the alkali metals only lithium, sodium and potassium could be separated from each other but rubidium and caesium always accompanied potassium. 相似文献
46.
Alinchenko MG Voloshin VP Medvedev NN Mezei M Pártay L Jedlovszky P 《The journal of physical chemistry. B》2005,109(34):16490-16502
The properties of the interatomic voids present in fully hydrated dimyristoylphosphatidylcholine (DMPC)-cholesterol mixed membranes of different compositions are analyzed in detail using a generalized variant of the Voronoi-Delaunay method on the basis of computer simulation results. The systems investigated are chosen from both sides of the DMPC-cholesterol miscibility gap; the pure DMPC bilayer has also been included in the analysis as a reference system. The results obtained show that the empty space is organized in a more compact way, forming larger voids in the presence than in the absence of cholesterol. The voids located in the region of the rigid cholesterol rings become, on average, less spherical, oriented more parallel with the membrane normal axis with increasing cholesterol concentration, whereas an opposite effect of cholesterol is observed in the middle of the membrane among the chain terminal methyl groups. In general, the preferential orientation of the voids is found to strongly correlate with that of the molecules in the hydrocarbon phase of the membranes. The membranes are found to contain rather large voids, the volume of which can be an order of magnitude larger than the largest spherical cavities present in the systems. These voids are elongated or branching channels rather than big empty holes. The voids located among the DMPC and cholesterol molecules are lying preferably parallel with the membrane normal axis. The existence of such empty channels can be of great importance in the cross-membrane permeation of small, uncharged penetrants, in particular, of polar molecules. 相似文献
47.
Giorgio Busetto 《Annali di Matematica Pura ed Applicata》1985,142(1):91-103
Sunto Siano G e
due gruppi, : GG una proiettività e N un sottogruppo normale di G. Vengono provati alcuni risultati sulle proprietà di immersions in
e G rispettivamente, del gruppi
, la chiusura normale di N in
modulo il nocciolo di N in
, e
.
Supported by a C.N.R. grant. 相似文献
Supported by a C.N.R. grant. 相似文献
48.
Giorgio Montaudo Emilio Scamporrino Daniele Vitalini Roberto Rapisardi 《Journal of polymer science. Part A, Polymer chemistry》1992,30(4):525-532
The low molecular weight compounds formed by partial ozonolysis of poly(isoprene) and poly(chloroprene) were analyzed by fast atom bombardment mass spectrometry (FABMS). In the poly(chloroprene) case, the ozonized mixtures were treated with piperidine before the MS analysis to transform in amide end groups the reactive acyl chlorides formed by the cleavage of double bonds along the main chain. Only one family of compounds having carboxyl and ketone or carboxyl and amide end groups were obtained from the ozonolysis of poly(isoprene) and poly(chloroprene), respectively. The assigned structures were confirmed by FAB-MS analysis of the GPC separation fractions [poly(chloroprene)] or by FAB-MS of the KOH-doped ozonolysis mixtures [poly(isoprene)]. It has been also ascertained, by GPC experiments, that poly(chloroprene) decomposes more rapidly than poly(isoprene) and poly(butadiene). 相似文献
49.
Reduction of enantiopure N-p-toluenesulfinyl ketimines derived from 2-pyridyl ketones affords N-p-toluenesulfinyl amines with good yields and diastereoselectivities. 相似文献
50.
N. M. Karpyak R. G. Makitra G. A. Marshalok E. Ya. Pal’chikova I. I. Yatchishin 《Russian Journal of General Chemistry》2006,76(2):272-277
The rate constants of cycloaddition of cyclopentadiene to unsaturated aldehydes in different solvents cannot be correlated with a single parameter, in particular, the Brownstein parameter. The data set can be fitted only by multiparameter equations in which the decisive factor increasing the reaction rate is the capability of a solvent for electrophilic solvation. The same parameter also governs the ratio of the endo and exo isomers of the addition product. 相似文献