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971.
Haiges R Vij A Boatz JA Schneider S Schroer T Gerken M Christe KO 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(2):508-517
The highly explosive molecules As(N(3))(3) and Sb(N(3))(3) were obtained in pure form by the reactions of the corresponding fluorides with (CH(3))(3)SiN(3) in SO(2) and purification by sublimation. The crystal structures and (14)N NMR, infrared, and Raman spectra were determined, and the results compared to ab initio second-order perturbation theory calculations. Whereas Sb(N(3))(3) possesses a propeller-shaped, pyramidal structure with perfect C(3) symmetry, the As(N(3))(3) molecule is significantly distorted from C(3) symmetry due to crystal packing effects. 相似文献
972.
p-Carborane has been vinylated on the 2-B-atom in high yields using the Heck reaction. Thus, the reaction between 2-iodo-p-carborane and various styrenes [4-H-, 4-C(6)H(4)-, 4-Cl-, 4-Br-, 4-NO(2)-, 4-CH(3)O-, and 4-CH(3)-] resulted in the production of the corresponding trans-beta-(2-B-p-carboranyl)styrene in DMF solution when reacted in the presence of silver phosphate and the palladacycle Herrmann's catalyst. 相似文献
973.
Stefan Müllegger Kathrin H?nel Thomas Strunskus Christof W?ll Adolf Winkler 《Chemphyschem》2006,7(12):2552-2558
Near-edge X-ray absorption fine structure (NEXAFS) spectroscopy has been applied to reveal the molecular arrangement of ultrathin oligophenyl films [p-quaterphenyl (4P) and p-hexaphenyl (6P)] on Au(111). In the half-monolayer films the molecules lie flat on the surface but still have a considerable inter-ring twist of 30 degrees -40 degrees , similar to the gas-phase conformation. In the saturated monolayer film the second half of the molecules is side-tilted by an angle of less than 66 degrees with respect to the surface. This arrangement is already similar to that in bulk net planes of thicker films parallel to the surface, that is, the 4P(211) and 6P(21-3) planes, respectively. 相似文献
974.
The preparation of pure Y3Al5O12 (YAG) and 50 vol% Al2O3–YAG
composite powders by a wet chemical route is presented. The role of the synthesis
temperature during reverse-strike precipitation has been investigated, showing
its relevant effect on the purity and homogeneity of YAG powder.
The
composite material was prepared by comparing two different synthesis routes.
A composite powder was synthesized via reverse-strike temperature-controlled
co-precipitation. In the latter case, a pure-alumina precursor was firstly
reverse-strike precipitated and then doped with an yttrium salt solution.
For both syntheses, the role of thermal and mechanical pre-treatments on the
phase development was demonstrated. 相似文献
975.
Reza Behjatmanesh-Ardakani 《Theoretical chemistry accounts》2007,118(4):799-805
In some works on the lattice Monte Carlo simulation of amphiphilic systems additional peaks in the cluster size distribution
has been interpreted as a clue for the phase or shape transition of micellar aggregates. On the other hand, some other works
showed that the additional peaks are a result of finite size of the lattice box. In this paper using calculating energy-auto-correlation
function and statistical error in correlated data, it is shown that how these apparently contradictory results are the same.
To do this, we have simulated a pure system containing amphiphile and water molecules. A simple model of potential containing
the main feature for these systems (the hydrophobicity of surfactant molecules) that cause the aggregates to be formed is
considered to avoid any synthetic results due to additional non-real parameters. To relax the initial configuration faster,
configurational bias Monte Carlo move is used in addition to reptation move. Periodic boundary condition and self-avoiding
walks are used as former published works in this field. It is shown that the additional peaks is a result of the statistical
errors for averaged cluster size distribution and can not be interpreted as a clue for shape or phase transition. 相似文献
976.
N. A. Mohamed Farook 《Journal of solution chemistry》2007,36(3):345-356
The oxidation kinetics of substituted and unsubstituted 4-oxoacids (S) by N-chlorosaccharin (NCSA) have been studied in aqueous acetic acid media. The reaction follows first-order kinetics in each
of the 4-oxoacids, NCSA and H+. The effect of changes in the electronic nature of the substrate reveals that positive charge develops in the transition
state. Based on the kinetic results and product analysis, a suitable mechanism has been proposed for the reaction of NCSA
with 4-oxoacids. 相似文献
977.
Electroactive conducting copolymers of aniline (ANI) and o-aminophenol (OAP) and two-layered poly(o-aminophenol) (POAP)/polyaniline (PANI) composites were prepared in aqueous acidic solution by electrode potential cycling.
Copolymerization was carried out at different feed concentrations of OAP and ANI on a gold electrode. A strong inhibition
of electropolymerization was found at a high molar fraction of OAP in the feed. The copolymers showed good adherence on the
electrode surface and gave a redox response up to pH=10.0. Two transitions were observed in the in situ conductivities of
the copolymers (as with PANI), but the conductivities were lower by 2.5–3 orders of magnitude as compared to PANI. Electrosynthesis
of PANI on POAP modified electrodes showed copolymer formation after reaction initiation and finally formation of a PANI layer
at the copolymer/solution interface. The ‘memory effect’ of the bilayer structures of both polymers was discussed in terms
of protonation/deprotonation and anion consumption taking place during redox processes of both polymers. 相似文献
978.
Stefan Meyer 《Monatshefte für Chemie / Chemical Monthly》1916,37(6):305-334
Zusammenfassung Es wurde mit Hilfe des schon früher beschriebenen Quarzapparates Thoriumbromid aus reinem Thoroxyd dargestellt, das nach zwei verschiedenen Methoden gereinigt war und auf Grund spektroskopischer Untersuchung als absolut rein und frei von seltenen Erden angesehen werden mu\te.Das geschmolzene Thorbromid wurde nach zwei Methoden analysiert und dabei die beiden VerhÄltnisse ThBr44 Ag und ThBr44 AgBr bestimmt.Zwei unabhÄngige Serien von 12, respektive 15 Analysen gaben die folgenden Resultate:Serie I. 54·45867g Thorbromid verbrauchten 42·58666g Silber und gaben 74·13448g Silberbromid, entsprechend einem Atomgewicht des Thoriums Th=232·15±0·016.Serie II. 74·30630g Thorbromid verbrauchten 58·11096g Silber und gaben 101·15848g Silberbromid, woraus sich das Atomgewicht Th=232·12±0·014 berechnet.Als Mittel dieser beiden Werte ergibt sich Th=232·135.Da aber die Analysenserie aus den oben besprochenen, uns triftig erscheinenden Gründen als die zuverlÄssigere angesehen werden mu\, glauben wir, da\ der aus ihr resultierende WertTh=232·12 als das derzeit wahrscheinlichste Atomgewicht des Thoriums anzusehen ist, wenn Ag=107·880 angenommen wird. Aus dem in 27 Bestimmungen gefundenen VerhÄltnis von angewandtem Silber zu gefundenem Silberbromid, AgAgBr= 0·574453, ergibt sich dann das Atomgewicht des Broms zu Br=79·916 in vollster übereinstimmung mit der von Baxter seinerzeit gefundenen Zahl. 相似文献
979.
Gamil A. Al-Hazmi Mohammed S. El-Shahawi Ahmed A. El-Asmy 《Transition Metal Chemistry》2005,30(4):464-470
The redox properties of the title mono- and binuclear copper(II) chelates have been investigated by cyclic voltammetry in DMF at a working platinum electrode. The cathodic reduction and anodic oxidation of the investigated chelates produced the corresponding electrochemical CuI and CuIIIspecies stable only in the voltammetric time scale, The effects of substituents on E1/2, redox properties and stability towards oxidation of the complexes were related to the electron-withdrawing or releasing ability of the substituents on the C=N1[H, CH3 or C6H5] and/or N4H [H, C2H5, C6H5 or pClC6H4] groups, The electron attracting substituents stabilize the Cu(II) complexes while electron-donating groups favor oxidation to Cu(III). Changes in the E1/2 for the complexes due to remote substituent effects could be related to changes in basicity of N4H.Thus, variation in N41-J has more influence on E1/2 than changes in C=N1. The correlation between E1/2 of the complexes and pKa of the ligands has been attributed to the spherical potential generated by the electron density of the donor atoms at the antibonding d orbitals. 相似文献
980.
A convergent diastereoselective synthesis of racemic aristoserratine ((±)- 24 ) via an intramolecular iminium-ion cyclization is described. The pivotal imine (±)- 19 was prepared by condensation of the two building blocks (± )-trans-8-amino-3-(2,6-difluorobenzyloxy)-1-p-menthene ((±)- 11 ) and N-(p-methoxybenzenesulfonyl)-3-indo-leacetaldehyde ( 18 ) which were synthesized from (±)-trans-1-p-menthene-3,8-diol ((±)- 7 ) and 3-indoleacetic acid, respectively. On the route to the target (±)- 24 , two previously unknown indole alkaloids have been characterized, namely (±)-‘anti’-hobartin-15-ol ((±)- 22 ) and (±)-‘anti’-aristotelin-15-ol ((±)- 23 ). 相似文献