摘要:

AbstractAn operationally simple oxidation of 5‐substituted pyrazol‐3(2H)‐ones to the corresponding methyl‐2‐alkynoates in good yields with a mediated poly[4‐(diacetoxyiodo)styrene] system in methanol and acetonitrile at room temperature was carried out. The polymeric reagent can be regenerated and reused as an environmentally ben

ISSN:0009-4536    

DOI:10.1002/jccs.200600132

出版商:WILEY‐VCH Verlag    

年代:2006

数据来源: WILEY

摘要:

AbstractA simple, rapid, precise and accurate kinetic method for simultaneous spectrophotometric determination of Nb(V) and Ta(V) is described. This method is based on the difference between the rate of the reaction of Nb(V) and Ta(V) with 4‐(2‐pyridylazo)resorcinol (PAR) in the presence of tartaric acid. H‐point standard addition method (HPSAM) was used to resolve the mixtures. The results showed that Nb(V) and Ta(V) can be determined simultaneously in the ranges of 0.10–5.0 and 0.50–12.0 μg mL−;1, respectively. The proposed method was successfully applied to the simultaneous determination of Nb(V) and Ta(V) in several a

ISSN:0009-4536    

DOI:10.1002/jccs.200600133

出版商:WILEY‐VCH Verlag    

年代:2006

数据来源: WILEY

摘要:

AbstractThe rate determining steps of isomericortho, metaandparanitrations of fluorobenzene and chlorobenzene have been theoretically investigated at the B3LYP/6‐311G* level. Stationary points of the step involving reactant, transition state and intermediate complexes were successfully located and characterized without any restriction on the internal coordinates. Their molecular geometries, electronic structures, IR spectra, and the FMO symmetries of two initial aromatic compounds and the NO2+suggest that the halogens areortho‐paradirective, and also activating substituents in the gas phase. The blue shift of the C‐N stretching vibration and the red shift of the tetrahedral C‐H stretching vibration from transition state to Wheland intermediate demonstrate that the formation of the C‐N and the cleavage of the C‐H are not concerted but stepwise at the rate determining step. This provides theoretical evidence for the experimental fact of the absence of primary kinetic isotopic effect in most aromatic nitration reactions. The fully optimized geometries of nitro‐chlorobenzene complexes show that the C‐Cl bond in nitro‐chlorobenzene complexes become much shorter than in chlorobenzene molecules and appears as a double bond. On the contrary, the C‐F bond in nitro‐fluorobenzene complexes is still a single bond, and even lengthens slightly as the NO2+moves toward the fluorobenzene. This reveals that there is a special interaction, namely inductomeric effect, between the chlorine and nitro group in nitro‐chlorobenzene complexes. The inductomeric effect may cause a marked increase in the percentage oforthoproduct for the nit

ISSN:0009-4536    

DOI:10.1002/jccs.200600134

出版商:WILEY‐VCH Verlag    

年代:2006

数据来源: WILEY

摘要:

AbstractThe electrochemical behavior of the Li+/Li couple was studied at polycrystalline tungsten, platinum, copper and aluminum electrodes in tri‐1‐butylmethylammonium bis((trifluoromethyl)sulfonyl)imide ionic liquid mixed with a little propylene carbonate at 30 °C. Lithium cations were introduced into the ionic liquid by dissolution of lithium bis((trifluoromethyl)sulfonyl)imide which is highly soluble in ionic liquid. Propylene carbonate was used to reduce the viscosity of this ionic liquid in order to enhance the mass transfer and to additionally improve the stability of lithium deposits. At the tungsten and copper electrodes, the cyclic voltammetric behavior of a Li+/Li couple is a quasi‐reversible reaction. At the platinum electrode, the behavior becomes very complicated because of the alloy formation. Coulombic efficiency was used to evaluate the stability of lithium deposits at each electrode. The aluminum electrode showed the best efficiency due to the formation of Li‐Al alloy. However, lowest efficiency was obtained at the platinum electrode because of the low redox reversibility of the lithium in the Li‐Pt alloy. The diffusion coefficient of lithium cation in this solution was 1.0 ± 0.1 × 10−;7cm2s−;1as determined by chronopotentiometry. The best coulombic efficiency obtained at the Al electrode is 97% but dropped to about 90% after 12 hours. The self‐discharge current of the lithium deposits at the Al electrode was 0.4 μA/cm2during the

ISSN:0009-4536    

DOI:10.1002/jccs.200600135

出版商:WILEY‐VCH Verlag    

年代:2006

数据来源: WILEY

摘要:

AbstractA novel quadridentate, N2O2type Schiff base, synthesized from 1,4‐bis‐(o‐aminophenoxy)butane and 2‐hydroxynaphthalin‐1‐carbaldehyde, forms stable complexes with transition metal ions such as Co(II), Cu(II) and Ni(II) in DMF. Microanalytical data, elemental analysis, magnetic measurements, UV‐visible and IR‐spectra as well as conductance measurements were used to confirm the structures. Electrochemical measurements show that metal complexes undergo quasi‐reversible one‐electron redox processes. The voltammetric results also revealed that the CuL complex has the highest electron transfer rate indicating that both the Cu(II) and Cu(I) forms appear in a similar planar configuration, so the electron transfer does not require larger reorganiza

ISSN:0009-4536    

DOI:10.1002/jccs.200600136

出版商:WILEY‐VCH Verlag    

年代:2006

数据来源: WILEY

摘要:

AbstractWe report here a substituent effect of diimines on the solid‐state assembly of interestingtrianguloPd(II) complexes, [(Pd(d‐t‐bpy))3(μJ3‐S)2][NO3]21·[NO3]2and [(Pd(bpy))3(μ3‐S)2][ClO4]22·[ClO4]2(d‐t‐bpy = 4,4′‐di‐tert‐butyl‐2,2′‐bipyridine, bpy = 2,2′‐bipyridine).2·[ClO4]2shows the intermolecular π···π interactions leading to the formation of one‐dimensional frameworks, whereas1·[NO3]2only shows the discrete structure in the solid state, featuring an interesting herring‐bone arrangement. The variation in structural motifs from1·[NO3]2to2·[ClO4]2is expected to be dominated by the substituent's steric hindrance for the diimine ligand. Thus, the crystal‐engineering approach has proved successful in the solid‐state packing due t

ISSN:0009-4536    

DOI:10.1002/jccs.200600137

出版商:WILEY‐VCH Verlag    

年代:2006

数据来源: WILEY

摘要:

AbstractA cobalt‐containing monodentate phosphine [(μ2‐PPh2CH2PPh2‐κ2P)Co2(CO)4][μ2‐η2‐PhC≡CP(i‐Pr)2]2f, was prepared from the reaction of (μ2‐PPh2CH2PPh2‐κ2P)Co2(CO)61with PhC≡CP(i‐Pr)2. It was accompanied by an oxidized compound, [(μ2‐PPh2CH2PPh2‐κ2P)Co2(CO)4][μ2‐η2‐PhC≡CP(=O)(i‐Pr2)]2foduring the chromatographic process. Further reaction of2fwith Mo(CO)6resulted in the formation of a2f‐ligated molybdenum complex4, [(μ2‐PPh2CH2PP

ISSN:0009-4536    

DOI:10.1002/jccs.200600138

出版商:WILEY‐VCH Verlag    

年代:2006

数据来源: WILEY

摘要:

AbstractSawdust ofDalbergia sissoo, a byproduct of sawmills, was found to be a promising adsorbent for the removal of nickel ions from aqueous solution. Sorption of nickel ions onto sawdust ofDalbergia sissoowas studied using the batch technique. Kinetics studies show that nickel ions sorption process obeys a first order rate law. The applicability of the Langmuir and Freundlich models for the data was tested. Both the models adequately describe the experimental data of the biosorption of nickel ions. The sorption capacities and energies were calculated. Langmuir parameters Xmand K1were found to increase with rise in temperature; Freundlich constants 1/n and Kfhave been evaluated for 293K, 303K, 313K and 323K. Thermodynamic parameter ΔH° = 4.80 kJ mol−;1shows that sorption of nickel ions onto sawdust is an endothermic proc

ISSN:0009-4536    

DOI:10.1002/jccs.200600139

出版商:WILEY‐VCH Verlag    

年代:2006

数据来源: WILEY

摘要:

AbstractFour common mesostructured aluminosilicates (e.g. AlMCM‐41, AlMCM‐48, AlMSU‐1 and AlSBA‐15, Si/Al = 7.5) with different pore framework structures were prepared via post‐synthetic method utilizing aluminum isopropoxide as the aluminating agent and characterized by27Al MAS NMR, XRD, N2‐adsorption isotherm and NH3‐TPD. It was found that, on the basis of the above analysis results, AlMCM‐41, AlMSU‐1 and AlSBA‐15 retained more mesoporosity than cubic Al/MCM‐48 after exposure to pure steam at 800 °C, which may be responsible for their much higher activities in bulky 1,3,5‐triisopropylb

ISSN:0009-4536    

DOI:10.1002/jccs.200600140

出版商:WILEY‐VCH Verlag    

年代:2006

数据来源: WILEY

摘要:

AbstractThis paper demonstrates the spectral analysis of some distillates obtained from asphalt cracking in the presence of a conventional expensive catalyst, i.e., HZSM‐5, and local cheap and readily available clay, i.e., UTIMAC. Each distillate was fractionated into pentane soluble (PI) and pentane insoluble (PI) fractions based on solubility in n, pentane. Both PS and PI obtained in the case of HZSM‐5 and UTIMAC were analyzed by1H‐NMR spectrophotometry using CDCl3as dissolving solvent and tetramethylsilane (TMS) as internal standard. It is evident from the profiles that both catalysts caused the generation of some peaks ascribed to methylene and methene configurations in the aliphatic region. Bands corresponding to aromatic configurations were also generated. The results indicate that the cheap local catalyst used has comparable suitability with the conventional expensive catalyst in terms of asphalt cra

ISSN:0009-4536    

DOI:10.1002/jccs.200600141

出版商:WILEY‐VCH Verlag    

年代:2006

数据来源: WILEY