摘要:

AbstractIt is a theoretical study on the water‐assisted mechanism of one‐carbon unit transfer reaction, in which the energy barrier for each aansition state lowered by about 80‐1100 kJ/mol when compared with the one in no‐water‐involved mechanism. The water‐assisted path 4 is the favorite reaction way. Our results well explained the presumption from

ISSN:1001-604X    

DOI:10.1002/cjoc.20040220602

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:2004

数据来源: WILEY

摘要:

AbstractThe La(III) complex with a new amide‐type tripodal ligand,2,2′.2″‐nitrilotris{[(2′‐benzylaminofomyl)‐phenoxylethyl)amine (L), was synthesized and characterized by X‐ray crystallographic analysis. Crystal data: C48H55.50LaN7O18.75,Mr=1169.40, monoclinic. space group,P21/n, a= 1.0644(3) nm. b=2.3889(5) nm, c= 2.1917(5) nm, β=90.65°, V=5.573(2) nm3, Z=1, Dc=1.394 g°cm−3,R1=0.0487, wR[1>2s̀(I)]=0.1266. The results reveal that each La(III) ion binds to 9 oxygen atoms, three of which belong to carbonyl groups from three tripodal ligands and six to three bidentate nitrate groups and a two‐dimensional sheet of 4.82networks is assembled by metal‐ligand coordination interaction. L, a heptadentate compound, merely acts as a tridentate bridging spacer due to its steric hindrance and links the La(III) ions

ISSN:1001-604X    

DOI:10.1002/cjoc.20040220603

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:2004

数据来源: WILEY

ISSN:1001-604X    

DOI:10.1002/cjoc.20040220604

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:2004

数据来源: WILEY

摘要:

AbstractBased on the thermokinetic theory, a novel thermokinetic research method‐self‐function regression method, which could be used to determine the kinetic parameters kl.k2andk‐1of the complex reaction: B +\documentclass{article}\usepackage{chemarr}\pagestyle{empty}\begin{document}${\rm C} \xrightleftharpoons[{k_{- 1}}]{{{\rm k}_{\rm 1}}} {\rm I} \xrightarrow[]{{\rm k}_{\rm 2}} {\rm P},$\end{document}, was proposed in this paper. The kinetics of the reaction of ascorbic acid (H2A) with hydrogen peroxide was investigated at pH=5‐7 and T=298.15 K, and the kinetic parametersk1k2andk‐1were obtained with this method. The kinetics of the reaction was investigated in detail. The kinetic parameters of the oxidation of ascorbic monoanion (HA−) and ascorbic dianion (A2‐) with hydrogen peroxide were 3.33×10−3s−1and 25.48 s−1at 298.15 K, respectively. The molar enthalpy change for the reaction was ‐554.64 kJ · mol−1in phosphate buffer solution

ISSN:1001-604X    

DOI:10.1002/cjoc.20040220605

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:2004

数据来源: WILEY

摘要:

AbstractThe adsorption of asymmetrical triblock copolymers from a non‐selective solvent on solid surface has been studied by using Scheutjens‐Fleer mean‐field theory and Monte Carlo simulation method on lattice model. The main aim of this paper is to provide detailed computer simulation data, taking A8‐kB20Akas a key example, to study the influence of the structure of copolymer on adsorption behavior and make a comparison between MC and SF results. The simulated results show that the size distribution of various configurations and density‐profile are dependent on molecular structure and adsorption energy. The molecular structure will lead to diversity of adsorption behavior. This discrepancy between different structures would be enlarged for the surface coverage and adsorption amount with increasing of the adsorption energy. The surface coverage and the adsorption amount as well as the bound fraction will become larger as symmetry of the molecular structure becomes gradually worse. The adsorption layer becomes thicker with increasing of symmetry of the molecule when adsorption energy is smaller but it becomes thinner when adsorption energy is higher. It is shown that SF theory can reproduce the adsorption behavior of asymmetrical triblock copolymers. However, systematic discrepancy between the theory and simulation still exists. The approximations inherited in the mean‐filed theory such as random mixing and the allowance of direct back folding may be responsible for those

ISSN:1001-604X    

DOI:10.1002/cjoc.20040220606

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:2004

数据来源: WILEY

摘要:

AbstractCubic boron nitride (cBN) and orthorhombic boron nitride (oBN) crystals have been prepared in hydrothermal solutions by reacting H3BO3+NaN3+P and H3BO3+NaN3+N2H4respectively. The experimental results indicated that, if the temperature was increased rapidly, both the yield and perfectness of BN crystals became poor. On the contrast, the yield and perfecmess of BN crystals can be improved very much by slowly increasing the temperature of the reaction mixture. The results of X‐ray powder diffraction (XRD), Fourier transform infrared spectrum (FTIR) and high resolution transmission electron microscopy (HRTEM) proved that the samples were composed of oBN and cB

ISSN:1001-604X    

DOI:10.1002/cjoc.20040220607

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:2004

数据来源: WILEY

摘要:

AbstractThe Ag2S2rings connect [Fe(NCS)5(DMF)]2‐(DMF=N,N‐dimethylformamide) octahedrons by bridging thiocyanates leading to a 3‐D [Ag2Fe(SCN)5(DMF)]nframework. The Fe(III) atoms are in the octahedral geometry and Ag(1) atoms are in the distoned tetrahedral geometry. One‐dimensional Ag2S2‐S‐Ag2S2wave‐like strand chains along the b‐axis and channels constructed from ten‐membered Ag2Fe(SCN)2S rings along the c‐axis feature the three‐dimensional framework. The Ag…Ag distance of 0.3103(1) nrn in Ag2S2rings indicates weak Ag…Ag interaction. Such an Ag2S2‐S‐Ag2S2chain in silver(I) complexes is unprecedented. Crystal data: M,=635.09, ortho‐rhombic,Pnma, a=1.64214(13) nm,b=1.40075(11) nm, c=0.84445(7) nm, V=1.9424(3) nm3, Z=4, μ(Mo Kα) =3.278 mm−1, Dcaled=2.172g × cm

ISSN:1001-604X    

DOI:10.1002/cjoc.20040220608

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:2004

数据来源: WILEY

摘要:

AbstractThe structure of dipepide AcMet‐Gly was determined by X‐ray crystallographic analysis. It possesses mono‐clinic, space groupP21(No. 4). with cell dimensions of α=0.8571(2) nm, b=0.5871(2) nm,c=1.197(3) nm, β= 99.290(10)°. V=0.5944(15) nm3, Z=2, μ=2.74 cm−1. Mononuclear chelates, described as[Pd(X)(S,N,O‐AcMet‐Gly)]−, in which Pd(II) is coordinated by thioether, deprotonated amide nitrogen, carbonyl oxygen of me‐thionine and X (AcMetGly or other ligands present in aqueous solution or in mobile phase solution), were detected 5 min after mixing AcMet‐Gly with [Pd(H2O)4]2‐at room temperature using electrospray ionization mass spectrometry. The geometry of [Pd(H2O)(S,N,O‐AcMet‐Gly)]−is optimized at density functional B3LYP/LanL2DZ level. The fused five‐ and six‐membered chelate is responsible for cleavage of Met‐Gly bond. This is the first time to provide a direct evidence for Pd(II)‐mediated cleavage of d

ISSN:1001-604X    

DOI:10.1002/cjoc.20040220609

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:2004

数据来源: WILEY

摘要:

AbstractA closed analytical relation is derived for the two‐center nuclear attraction integrals over Slater type orbitals (STOs) in terms of binomial coefficients. This formula can be used in highly accurate calculations of the nuclear attraction integrals. The relationships obtained are valid for arbitrary values of quantum numbers and screening constants of STOs and location of nucle

ISSN:1001-604X    

DOI:10.1002/cjoc.20040220610

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:2004

数据来源: WILEY

摘要:

AbstractIonic liquids are a type of salts that are liquid at low temperature (<100 °C). Because of their some special properties, they have been widely used as new “green solvents” for many chemical reactions and liquid‐liquid extraction in the past several years. In this paper, a new method for the separation of nucleotides is developed and the essential feature of the method is that 1‐alkyl‐3‐methylimidazolium salts are used as mobile phase additives, resulting in a baseline separation of nucleotides without need of gradient elution and need of organic solvent addition as currently used in RP‐HPLC. This study shows the potential application of ionic liquids as mobile phase additives in reversed‐phase liqui

ISSN:1001-604X    

DOI:10.1002/cjoc.20040220611

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:2004

数据来源: WILEY