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181.
182.
Yi Yuan Zong-Lin Jiang Jia-Ming Yan Ge Gao Albert S. C. Chan Ru-Gang Xie 《合成通讯》2013,43(24):4555-4561
Two new macrobicyclic imidazolium and benzimidazolium phanes were synthesized by direct quaternization of the corresponding tripodal azacycles with tribromide under high dilution condition in excellent yields. The cyclophanes were identified by 1H-NMR, 13C-NMR, FAB-MS, IR, elemental analysis and X-ray diffraction analysis. 相似文献
183.
Julie A. Griffith-dzielawa Richard E. Barrans Jr. Daniel R. Mcalister Mark L. Dietz Albert W. Herlinger 《合成通讯》2013,43(12):2121-2132
A homologous series of alkylenediphosphonic acids was successfully esterified with 3-(trimethylsilyl)-1-propanol to the symmetrically-substituted diesters. The procedure, which has general applicability for incorporating silicon heteroatoms into diphosphonic acids, utilizes the esterification reagent dicyclohexyl-carbodiimide (DCC) to activate the acid. The aggregation properties of the di-[3-(trimethylsilyl)-1-propylene] alkylenediphosphonic acids were measured in toluene and 1-decanol. 相似文献
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185.
The pressure-temperature phase diagram of n-octyl-isothiocyanato-biphenyl (8BT) in the pressure range up to 250 MPa (2.5 kbar) and the temperature range 250-400 K was established with the aid of DTA. At 1 atm the substance exhibits exclusively CrE polymorphism. At pressures above 190 MPa, the clearing line splits showing an additional phase which is not yet identified. Dielectric relaxation measurements on the CrE phase of 8BT were performed in the pressure range 0.1-120 MPa and the temperature range 304-345 K. A Debye-type relaxation process was observed in the frequency range 100 Hz-1 MHz. The longitudinal relaxation time τ, characterizing the molecular reorientations around the short axis, was analysed with respect to the pressure and temperature, yielding the activation volume, Δ# V = RT(? ln τ/?p)T, and activation enthalpy, Δ# H = R(? ln τ/? T-1)p, respectively. The results are compared with analogous data obtained recently for similar compounds having other liquid crystalline phases (N, SmA). 相似文献
186.
187.
Andrew J. Thompson Dr. Jerome Dabin Javier Iglesias‐Fernández Dr. Albert Ardèvol Dr. Zoran Dinev Assoc. Prof. Spencer J. Williams Dr. Omprakash Bande Dr. Aloysius Siriwardena Carl Moreland Dr. Ting‐Chou Hu David K. Smith Prof. Harry J. Gilbert Prof. Carme Rovira Prof. Gideon J. Davies 《Angewandte Chemie (International ed. in English)》2012,51(44):11171-11171
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189.
ABSTRACTThe reaction of formic acid (HCOOH) with chlorine atom and amidogen radical (NH2) have been investigated using high level theoretical methods such BH&HLYP, MP2, QCISD, and CCSD(T) with the 6–311?+?G(2df,2p), aug-cc-pVTZ, aug-cc-pVQZ and extrapolation to CBS basis sets. The abstraction of the acidic and formyl hydrogen atoms of the acid by the two radicals has been considered, and the different reactions proceed either by a proton coupled electron transfer (pcet) and hydrogen atom transfer (hat) mechanisms. Our calculated rate constant at 298?K for the reaction with Cl is 1.14?×?10?13?cm3?molecule?1?s?1 in good agreement with the experimental value 1.8?±?0.12/2.0?×?10?13?cm3?molecule?1?s?1 and the reaction proceeds exclusively by abstraction of the formyl hydrogen atom, via hat mechanism, producing HOCO+ClH. The calculated rate constant, at 298?K, for the reaction with NH2 is 1.71?×?10?15?cm3?molecule?1?s?1, and the reaction goes through the abstraction of the acidic hydrogen atom, via a pcet mechanism, leading to the formation of HCOO+NH3. 相似文献
190.
R. Rubio J. Albertí G. Rauret 《International journal of environmental analytical chemistry》2013,93(1-4):203-213
Abstract A photolytic method, which uses UV irradiation (254 nm) and K2S2O8 in alkaline media has been optimized for the speciation of arsenite, arsenate, monomethylarsonic and dimethylarsinic acid, arsenobetaine and arsenocholine. Under these conditions it is possible to obtain not only simple species from arsenobetaine and arsenocholine with good yields, but also to establish the optimum conditions to carry out the process on-line with HG-ICP/OES for the determination of these species. The products obtained in the photolytic reaction are introduced into the reduction chamber to form arsines. According to the results obtained from the ICP measurements, the recoveries obtained are about 100% and the procedure has a good reproducibility. 相似文献