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161.
Zyryanov GV Kang Y Stampp SP Rudkevich DM 《Chemical communications (Cambridge, England)》2002,(23):2792-2793
Reaction of NO2 with simple calix[4]arenes in chloroform in the presence of a Lewis acid rapidly results in intense coloration caused by the encapsulation of nitrosonium cation. 相似文献
162.
163.
Kang EJ Cho EJ Ji MK Lee YE Shin DM Choi SY Chung YK Kim JS Kim HJ Lee SG Lah MS Lee E 《The Journal of organic chemistry》2005,70(16):6321-6329
(+)-SCH 351448 (Na+ salt A) was synthesized employing ring-closing olefin metathesis reaction of an open diene diester intermediate for construction of the 28-membered macrodiolide structure. The open diene diester was prepared from the monomeric hydroxy carboxylic acid and two different olefin fragments. The monomeric hydroxy acid was synthesized via Julia-Julia coupling reaction of intermediates derived from the same olefinic fragments. Oxane units in these fragments were prepared by radical cyclization reactions of beta-alkoxyacrylates. Analogous SCH 351448 salts incorporating other mono- and divalent cations may be prepared. Under acidic conditions, SCH 351448 (Na+ salt A) was the most stable complex, but SCH 351448 (Ca2+ salt) and (Na+ salt B) appear to be physiologically important species. 相似文献
164.
The separation of wide molecular mass (Mr) ranges of macromolecules using frit inlet asymmetrical flow field-flow fractionation (FI-AFlFFF) has been improved by implementing a combination of field and flow programming. In this first implementation, field strength (governed by the cross flow-rate through the membrane-covered accumulation wall) is decreased with time to obtain faster elution and improved detection of the more strongly retained (high Mr) materials. The channel outlet flow-rate is optionally held constant, increased, or decreased with time. With circulation of the flow exiting the accumulation wall to the inlet frit, the dual programming of cross flow and channel outlet flow could be implemented using just two pumps. With this flow configuration, the channel outlet flow-rate is always equal to the channel inlet flow-rate, and these may be programmed independently of the cross flow-rate through the membrane. FI-AFlFFF retains its operational advantage over conventional asymmetrical flow FFF (AFlFFF). Unlike conventional AFlFFF, FI-AFlFFF does not require time consuming, and experimentally inconvenient, sample focusing and relaxation steps involving valve switching and interruption of sample migration. The advantages of employing dual programming with FI-AFlFFF are demonstrated for sets of polystyrene sulfonate standards in the molecular mass range of 4 to 1000 kDa. It is shown that programmed FI-AFlFFF successfully expands the dynamic separation range of molecular mass. 相似文献
165.
The dicobalt octacarbonyl catalyzed reaction of styrene oxide with trialkylsilanes yields a mixture of 1-phenyl-2-trialkylsiloxyethane and Z- and E-1-phenyl-2-trialkylsiloxyethene. The ratio of these products can be controlled. 相似文献
166.
Two new charge-transfer hybrids with one or two ferrocenyl units covalently attached to a hexamolybdate cluster through an extended pi-conjugated bridge have been prepared using Pd-catalyzed coupling reactions on monoiodo- or diiodo-functionalized cluster substrates in over 60% yields. These hybrids have been characterized by (1)H NMR, FTIR, electrospray ionization mass spectrometry, and X-ray diffraction. The electronic spectra of these hybrids show a broad absorption tail extending beyond 550 nm, indicating the existence of charge-transfer transition from the ferrocenyl donor to the cluster acceptor. The observation of the clear charge-transfer transition indicates the contribution of charge-transfer resonance to the ground state in both 2a and 2b even though the donor-acceptor separation distance of 11.29 A is rather long, signaling a through-bond charge-transfer nature made possible by the organic pi-conjugated bridge. Cyclic voltammetry studies reveal a one-electron oxidation wave and a one-electron reduction wave for the hybrid with one ferrocenyl unit. For the one with two ferrocenyl units, a lower reduction potential and a two-electron oxidation wave are observed, indicating negligible electronic interactions between the two ferrocenyl units. 相似文献
167.
The catalyst reactivity and reusability for the lanthanide triflate-catalyzed three component synthesis of alpha-amino phosphonates have been examined in room temperature ionic liquids, [bmim][X], in which the catalytic activities were very dependent on the counter anion, X, as well as on the phosphorus nucleophile, and moreover, the catalyst immobilized in an ionic liquid was reused several times without any loss of activity. 相似文献
168.
The calculations of the electronic structure and conformational analysis of the acetanilide were carried out using the CNDO/2 method. The results show that the endo form is 1.2 Kcal/mole more stable than the exo form. The most stable conformation of the exo isomer corresponds to the dihedral angle of 90 ° between the phenyl and acetamide plane, whereas the minimum energy conformation of the endo isomer corresponds to the dihedral angle 50 °–60 °. A comparison of the calculated and experimental dipole moments suggests also the dihedral angle of 50 °–60 °. A comparison with experiment indicates that this molecular orbital method is good for conformational analysis and gives electronic structure which is compatible with spectroscopic measurement. The calculated conformational analysis and electronic structure of the acetanilide are in excellent agreement with experiments.We thank Professor J. P. Green for helpful discussions. This research was supported by a grant from the National Institute of Mental Health (MH-17489-01). 相似文献
169.
Kang MS Kim JH Kim YJ Won J Park NG Kang YS 《Chemical communications (Cambridge, England)》2005,(7):889-891
The ionic conductivity of polymer electrolytes and their interfacial contact with dye-attached TiO2 particles were enhanced markedly by the addition of amorphous oligomer into polymer electrolytes, resulting in very high overall energy conversion efficiency. 相似文献
170.
JongHwa Moon SangHoon Kang YongSam Chung OkHee Lee 《Journal of Radioanalytical and Nuclear Chemistry》2007,271(1):155-158
Instrumental neutron activation analysis was used to assess the concentration of the inorganic trace elements in Korean women’s
blood serums. It was found that a high concentration of Na and Cl incurs an analytical interference, but the 12 elements such
as Br, Ca, Cl, Co, Cr, Cs, Fe, K, Na, Rb, Se and Zn could be determined under the condition of an interference minimization.
Serum samples collected from 63 women were analyzed and the concentration level and range of the elements were evaluated.
NIST SRMs were analyzed simultaneously for quality control. The average values of the Na and Cl determined in the serum samples
were 3,365 and 3,533 mg/l, Ca was 96.4 mg/l and K was 191 mg/l. Besides, Br, Se and Zn have a concentration level of 6.46,
0.13 and 0.98 mg/l, respectively. It was found that there is no significant difference between the present values and the
reported values. 相似文献