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61.
Lim LW Hirose K Tatsumi S Uzu H Mizukami M Takeuchi T 《Journal of chromatography. A》2004,1033(2):205-212
An on-line sample enrichment system was designed using monolithic precolumns in microcolumn LC. The monolithic ODS capillary columns were prepared via in situ sol-gel processes. The enrichment efficiency of the monolithic columns was tested by using phthalates as the analytes. The relative standard deviations (n = 6) for the retention time, peak area and peak height were between 0.4 and 1.2%, 0.9 and 5.5% and 0.4 and 3.9%, respectively. The system was linear (R2 > 0.99) within the working sample concentration and sample volume ranges. Comparing to 0.2 microl injection with a typical sample injector, the theoretical plate number of a same separation column was increased by 3-6-fold when the precolumn unit was used for sample injection. The recoveries of the analytes were between 88 and 120%, and the sample volume that could be injected into the system was increased up to 5000-fold. The limits of detection were improved by more than 2000-fold and were between 0.21 and 0.87 ng ml(-1) even with a UV absorbance detector. This system was applied to the determination of phthalates contained in laboratory distilled water and tap water samples. 相似文献
62.
Stasko DJ Perzynski KJ Wasil MA Brodbeck JK Kirschbaum K Kim YW Lind C 《Inorganic chemistry》2004,43(13):3786-3788
The acid H(2)B(12)(OH)(12) can be isolated as a crystalline solid by protonation of the hydroxylated borane anion, B(12)(OH)(12)(2)(-). This acidic compound has low solubility in water, conducts protons in the solid state, and has thermal stability to a temperature of 400 degrees C. The conductivity mechanism is a Grotthuss mechanism with a low activation enthalpy (9-13 kcal/mol). This new acid represents an addition to the class of oxoacids, of which sulfuric and phosphoric acid are the most prominent examples. 相似文献
63.
Martyn A. Brown Bruce R. McGarvey Andrzej Ozarowski Dennis G. Tuck 《Journal of organometallic chemistry》1998,550(1-2)
The primary process in the reaction of hexaphenylditin with various substituted orthoquinones (Q) is shown to involve attack by the quinone at a phenyl ligand. The intermediate thus formed decomposes to yield Ph3Sn(SQ·), where S(Q·−) is the corresponding semiquinonate. Rearrangement of these species in solution gives rise to biradicals, while intramolecular electron transfer may lead to the formation and precipitation of Ph2Sn(CAT), where CAT2− is the corresponding substituted catecholate. The identification of these processes depends in part on electron paramagnetic resonance spectroscopy. The reaction of Ph3SnCl or Ph2SnCl2 with Na(TBSQ·) (TBSQ·−=3,5-di-tert-butyl-orthobenzosemiquinonate) results in the formation of Ph2Sn(TBSQ·), which can undergo redistribution and intramolecular electron transfer, so that the solution chemistry of these latter systems is similar to that of the products of the Sn2Ph6+Q reaction. 相似文献
64.
The phosphapalladacycle derived from 1-(2',5'-dimethylphenyl)ethyldiphenylphosphine has been prepared in the optically active and racemic forms. The phosphine was synthesized as a racemate by the treatment of 1-chloro-1-(2',5'-dimethylphenyl)ethane with sodium diphenylphosphide in THF. The racemic phosphapalladacycle was subsequently obtained as the chloro-bridged dimer by the treatment of the phosphine with palladium(II) acetate followed by anion metathesis with lithium chloride. Alternatively, the phosphine could be optically resolved via metal complexation using (R,R)-bis(mu-chloro)bis{1-[1-(N,N-dimethylamino)ethyl]naphthyl-C(2),N}dipalladium(II) as the resolving agent. An efficient separation of the resulting diastereomeric complexes was achieved by silica gel chromatography. The obtained optically resolved diastereomers were next subject to chemoselective removal of the (R)-N,N-(dimethylamino)-1-(1-naphthyl)ethylaminate auxiliary by treatment with concentrated hydrochloric acid. This process yielded the binuclear dimer complexes containing the resolved eta(1)-P ligand. Cyclopalladation of the coordinated phosphine could next be performed by treatment of its eta(1)-P binuclear dimer with silver(I) hexafluorophosphate(V) in a dichloromethane/water mixture followed by treatment with lithium chloride, giving rise to a pair of optically pure enantiomeric dimers with [alpha](D) -322 and +319 degrees in CH(2)Cl(2). Despite the possibilities of the phosphine to attain a five- membered structure by ortho-palladation or a six-membered ring formation by aliphatic C-H bond activation, only the former was observed. X-ray crystallographic data of the meso dimer and an acetylacetonate derivative indicated that the phosphapalladacycle alpha-C methyl substituent was axially located. The 2-D (1)H-(1)H ROESY spectrum of the acetylacetonate derivative further revealed that the phosphapalladacycle was conformationally rigid in CDCl(3). 相似文献
65.
The reactions of π-cyclopentadienylnickel carbonyl dimer with 3,3,3-trimethylpropynyldiphenylphosphine and phenylethynyldiphenylphosphine are described. The products have been characterized by elemental and mass spectral analysis, infrared and NMR spectroscopy. An acetylene bridged complex (π-C5H5Ni)2Ph2PC2-t-Bu, containing an uncoordinated phosphorus atom, has been prepared. The complex can be oxidized to the phosphine oxide derivative (π-C5H5Ni)2Ph2P(O)C2-t-Bu and converted to the phosphonium salts with methyl iodide or ethyl bromide. These are the first reported π-complexes of phosphonium salts. The complex (π-C5H5Ni)2Ph2PC2-t-Bu forms the novel mixed metal derivative [PdCl2][(π-C5H5Ni)2Ph2PC2-t-Bu]2 from bis(benzonitrile)-palladium dichloride. The dicarbonyl complexes Ni(CO)2(Ph2PC2R)2 (R t-Bu, Ph), the phosphine oxide complex (π-C5H5Ni)2(Ph2P(O)C2Ph) and the trinuclear nickel carbonyl derivative Ni(CO)3[(π-C5H5Ni)2Ph2PC2Ph] are described. 相似文献
66.
Experimental data on initial hydrate formation conditions have been obtained for the nitrogen-propane-water system in the L1HG, L1L2H, and L1L2HG regions, where L1 is the water rich liquid phase, L2 is the hydrocarbon rich liquid phase, H is the hydrate and the G is the vapor phase. The measurements covered a range of temperatures from about 275 to 293 K and pressures from about 0.3 to 17.0 MPa. The concentrations covered for the L1HG region extended from 0.94 to 75.0 mole percent propane in the gas phase, and for the L1L2H region they extended from 83.1 to 99.0 mole percent in the condensed liquid phase. Four-phase measurements were made at concentrations of propane from 18.1 to 71.1 mole percent in the gas phase.The experimental data were used to find a fitted binary interaction parameter for predicting hydrate formation in systems containing nitrogen and propane. 相似文献
67.
Ming‐Liang Tong Wei Li Xiao‐Ming Chen Shao‐Liang Zheng Seik Weng Ng 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(4):m232-m234
The title compound, [Cu2(C2H3O2)4(C11H9N)2] or [Cu2(MeCO2)4(phpy)2] (phpy is 4‐phenylpyridine), consists of centrosymmetric dimers in which the CuII atoms display a square‐pyramidal CuO4N coordination, with four acetate O atoms in the basal plane [Cu—O 1.975 (3)–1.987 (3) Å] and the phpy N atom in the apical position [Cu—N 2.150 (3) Å]. The Cu atoms are 2.654 (1) Å apart and are bridged by four acetate groups. The discrete dimers are extended into a three‐dimensional supramolecular array through intermolecular π–π‐stacking interactions. 相似文献
68.
Gas-phase activation energies were calculated for three lithium enolate reactions by using several different ab initio and density functional theory (DFT) methods to determine which levels of theory generate acceptable results. The reactions included an aldol-type addition of an enolate to an aldehyde, a proton transfer from an alcohol to a lithium enolate, and an S(N)2 reaction of an enolate with chloromethane. For each reaction, the calculations were performed for both the monomeric and dimeric forms of the lithium enolate. It was found that transition state geometry optimization with B3LYP followed by single point MP2 calculations generally provided acceptable results compared to higher level ab initio methods. 相似文献
69.
The dorid nudibranch Archidoris odhneri produces (all E)-2,3-dihydroxypropylfarnesate and its two monoacetoxy derivatives. 相似文献
70.
Bian Y Li L Dou J Cheng DY Li R Ma C Ng DK Kobayashi N Jiang J 《Inorganic chemistry》2004,43(23):7539-7544
Three (1,8,15,22-tetrasubstituted phthalocyaninato)lead complexes Pb[Pc(alpha-OR)(4)] [H(2)Pc(alpha-OC(5)H(11))(4) = 1,8,15,22-tetrakis(3-pentyloxy)phthalocyanine; H(2)Pc(alpha-OC(7)H(15))(4) = 1,8,15,22-tetrakis(2,4-dimethyl-3-pentyloxy)phthalocyanine; H(2)Pc(alpha-OC(10)H(7))(4) = 1,8,15,22-tetrakis(2-naphthyloxy)phthalocyanine] (1-3) have been prepared as racemic mixtures by treating the corresponding metal-free phthalocyanines H(2)Pc(alpha-OR)(4) (4-6) with Pb(OAc)(2).3H(2)O in refluxing n-pentanol. The molecular structure of Pb[Pc(alpha-OC(5)H(11))(4)] (1) in the solid state has been determined by single-crystal X-ray diffraction analysis. This compound, having a nonplanar structure, crystallizes in the monoclinic system with a P2(1)/c space group. Each unit cell contains two pairs of enantiomeric molecules, which are linked by weak coordination of the Pb atom of one molecule with an aza nitrogen atom and its neighboring oxygen atom from the alkoxy substituent of another molecule, forming a pseudo-double-decker supramolecular structure in the crystals with a short ring-to-ring separation, 2.726 A, and thus a strong ring-ring pi-pi interaction. The decreased molecular symmetry for these complexes has also been revealed by the NMR spectra of 1 and 2. The methyl protons of the 3-pentyloxy and 2,4-dimethyl-3-pentyloxy side chains of 1 and 2, respectively, are chemically inequivalent. In addition to the elemental analysis and various spectroscopic characterizations, these compounds have also been electrochemically studied. Two one-electron oxidations and up to five one-electron reductions have been revealed by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) methods. 相似文献