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41.
Jeffrey Axten Jennifer Troy Peter Jiang Mendel Trachtman Charles W. Bock 《Structural chemistry》1994,5(2):99-108
Ab initio molecular orbital calculations are used to study the modified Schlenk equilibrium: 2RMgCl (RMgCl)2 MgR2 + MgCl2 Mg(Cl2)MgR2 with R=H and CH3. In the absence of any solvents, calculations indicate that the formation of the various possible bridged dimers (RMgCl)2 is substantially exothermic. However, using dimethylether as a model solvent, we show that the formation of the dimer (Me2O)(CH3)Mg(Cl2)Mg(CH3)(OMe2) is exothermic only when entropic effects are included. 相似文献
42.
43.
Erika S. Eichmann Jennifer S. Brodbelt 《Journal of the American Society for Mass Spectrometry》1993,4(3):230-241
The reactions of dimethyl ether ions with neutral amino alcohols were examined in both a quadrupole ion trap mass spectrometer and a triple quadrupole mass spectrometer. These ion-molecule reactions produced two types of ions: the protonated species [M+l]+ and a more complex product at [M+13]+. The abundance of the [M+13]+ ions relative to that of the [M+1]+ ions decreases with increasing formal interfunctional distance. Multistage collision-activated dissociation techniques were used to characterize the [M+13]+ product ions, their reactivities, and the mechanisms for their formation and dissociation. In addition, molecular semiempirical calculation methods were used to probe the thermochemistry of these reactions. Reaction at the amino alcohol nitrogen site is favored, and the resulting [M+13]+ addition products may cyclize for additional stabilization. Comparisons were made among the behavior of related compounds, such as alcohols, diols, amines, and diamines. The alcohols reacted only to form the protonated species, but the diols, amines, and diamines all formed significant amounts of [M+13]+ ions or related dissociation products. 相似文献
44.
The 13C NMR spectra of a number of iridium complexes and of their adducts with H2, HX, and Cl2 (X = Cl, Br, I) are used to estimate the redox character of these additions. Rather than having the oxidative character expected, H2 addition seems to be reductive. HX and Cl2 additions are oxidative. Some of these complexes appear to have Lewis acid, rather than the expected Lewis base character. 相似文献
45.
Springfield SA Marcantonio K Ceglia S Albaneze-Walker J Dormer PG Nelson TD Murry JA 《The Journal of organic chemistry》2003,68(11):4598-4599
In this paper, we disclose an efficient one-pot procedure for the preparation of substituted 1,8-naphthyridin-4-one analogues. Previous efforts to effect this type of transformation were complicated by the formation of benzene tricarboxylate. Via the use of excess base, the impurity formation was completely inhibited. This allowed for the clean preparation of the desired intermediate and subsequent formation of naphthyridone analogues in a single flask, which could then be crystallized directly from the reaction mixture in good yield and high purity. 相似文献
46.
Michael I. Bruce Jennifer K. Walton Michael L. Williams Brian W. Skelton Allan H. White 《Journal of organometallic chemistry》1981,212(3):C35-C38
Contrary to some previously depicted structures, the proton in HC5(CO2Me)5 is bonded to two oxygens rather than to carbon; the lithium ion in Li[C5(CO2Me)5] (H2O) is tetrahedrally coordinated by two carbonyl oxygens from one C5 anion, one from a second anion, and a water molecule. 相似文献
47.
NaTaO3 nanorods were synthesized with high (>90%) yield by reduction of TaCl5 with THF solutions of the alkalide K+(15C5)2Na-, followed by product annealing under dynamic vacuum at 250 and 600 degrees C. In addition to the nanorods, the product is comprised of 5-10% approximately 10-nm diameter spheroidal NaTaO3 nanocrystals. The nanorods are generally longer than 500 nm, with some exceeding 1 mum, and 10-100 nm wide, with aspect ratios that vary between 10 and 20:1. Select area electron diffraction patterns of individual nanorods indicate that each nanorod is a single crystal with its axis oriented in the [010] direction. 相似文献
48.
Three-dimensional (3-D) structures with micron-sized features have been fabricated via the direct-write assembly of polyelectrolyte inks. By mixing oppositely charged species under solution conditions that promote polyelectrolyte exchange reactions, we have created concentrated fluids capable of flowing through microscale deposition nozzles. Ink deposition into an alcohol/water coagulation reservoir yielded polyelectrolyte filaments that rapidly solidify to enable three-dimensional patterning of microperiodic structures with self-supporting features. The influence of ink and reservoir chemistry on the phase behavior, rheological properties, and assembly of concentrated polyelectrolyte complexes is reported with an emphasis on the optimal conditions for 3-D writing. 相似文献
49.
J.William Suggs S.D. Cox Robert H. Crabtree Jennifer M. Quirk 《Tetrahedron letters》1981,22(4):303-306
The title complex readily hydrogenates a number of hindered steroidal olefin groups from the α face, without reducing ketone carbonyl groups, carbon—halogen bonds or cyclopropane rings. 相似文献
50.
Rory?H.?Uibel Emily?C.?Heider Jennifer?L.?Gasser Joel?M.?HarrisEmail author Edward?M.?Eyring Sergio?Petrucci 《Journal of solution chemistry》2005,34(5):499-514
Advances have been made recently in broadening the accessible ultrasonic absorption frequency range and improving the detectability of minor species present in solution using Raman spectroscopy. Development of chemometric techniques in these areas needs to keep pace with the improvement of these experimental methods. Refinements in the analysis of ultrasonic and Raman data based on multivariable least squares and factor analysis, respectively, are examined to investigate the kinetics of zinc thiocyanate complex formation in water. Analysis of ultrasonic absorption relaxation spectra verified that the observed process in aqueous Zn(SCN)2 involves substitution of water from the first coordination shell of Zn2+. Use of a multivariable least-squares error surface is described that enhances the reliability of assigned frequencies of ultrasonic absorption maxima. Factor analysis of Raman scattering data provided direct evidence that at least four complex species, such as Zn(SCN)+ and Zn(SCN)2, are simultaneously present in the aqueous zinc thiocyanate solutions. 相似文献