摘要:

AbstractBased on five thermodynamic equilibria among the components I, II, and adsorbent, a stoichiometric displacement model of adsorption (SDM‐A) from binary liquid mixture with complete range of concentration in liquid‐solid system is proposed and tested by using data published in literatures. The two expressions of this model show the quantitative relationships between the activity of the component I on the surface and that in the bulk solution and between its partition coefficient in two phases and its equilibrium activity in bulk solution, respectively. In some cases, the two expressions may become two linear equations, from which the correspondingly linear slopes (i.e. the adsorption parameters) are obtained with which the stoichiometric displacement relation and relative adsorption ability between components I and II can be elucidated. The effectiveness of these two expressions for different adsorption systems and the similarity and difference between SDM‐A and the Freundlich Empirical Equation are also investigated. A rule illustrating a parallel relationship between 2n/Zand the property of bulk solution is also found. And, having studied the quantitative relation of the adsorption from either ideal or non‐ideal liquid mixture and compaired their linear adsorption parameters, we find that SDM‐A is much better than the L

ISSN:1001-604X    

DOI:10.1002/cjoc.19930110501

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

年代:1993

数据来源: WILEY

摘要:

AbstractIn this work, the time development of surface enhanced Raman intensities of the vibrational modes involving the ring skeleton and the C—H motions of the pyrazine molecule as the applied voltage on the silver electrode is shifted between −0.2 V and −0.5 V (vs.saturated calomel electrode) is reported. The observation shows that there are two processes of enhancement involved during this shift of applied voltage. One is vibrational mode dependent while the other is not. The detailed behavior of these two processes of enhancement is discussed along with the retarded response of the Helmholtz double layer structure to the change of the applied voltage on the elec

ISSN:1001-604X    

DOI:10.1002/cjoc.19930110502

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe crystal structure of 2,3‐benzo‐1,4,7,13‐tetraoxa‐10‐selenacyclopentadeca‐2‐ene was determined. C14H20O4Se,Mr=331.27, orthorhombic,Pbca, a=18.445(3) Å,b=16.334(4) Å,c=9.232(2) Å,V=2781.3 Å3,Z=8,Dx=1.582 Mg m−3, λ(MoKα)equals;0.71073 Å, μequals;26.77 cm−1,F(000)equals;1360,T=297 K,R=0.0329,Rw=0.0438 for 2192 reflections withI>3 s̀(I). The crystal structure is closely related to that of benzo‐15‐crown‐5 (at 123 K), whereas the molecular geometry of the two coronands is different according to their torsion angles cal

ISSN:1001-604X    

DOI:10.1002/cjoc.19930110503

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

年代:1993

数据来源: WILEY

摘要:

AbstractIn this paper a series ofab initioSCF and configuration calculations were reported for the ground state and excited states X2E, A2E,2B2and2A1of allene. For ground state X2E Jahn‐Teller distorsion was discussed and a twisted angle of 50° and a torsional barriers of 0.21–0.51 eV were derived. Based on calculated results, the experimental photoelectron spectrum of allene has been assi

ISSN:1001-604X    

DOI:10.1002/cjoc.19930110504

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

年代:1993

数据来源: WILEY

摘要:

AbstractThermal decomposition of supported magnesium formate has been studied by gas chromatography. The reaction paths of decomposition of supported magnesium formate depend on the nature of the supports. For Mg(HCO2)2/HZSM‐5, the zeolite behaves as a dehydration catalyst to give CO and H2O at lower temperatures; when the zeolite is modified by phosphorus, the methanation reaction will be partly restrained. In the case of Mg(HCO2)2/AC, strong adsorption of CO2leads to the formation of the shoulder peak of CO2at higher temperatures, however, CH4disappears after modified by phosphorus. For Mg(HCO2)2/Al2O3, the dehydrogenation of HCO2−takes place on the surface of Al2O3. The decomposition of Mg(HCO2)2on SiO2in hydrogen yields two peaks of CO and only one appears after modified by phosphorus. When Mg(HCO2)2decomposes on MgO, the first peak of CO2arises from the reaction of surface Mg2+with HCO2−from dissociated Mg(H

ISSN:1001-604X    

DOI:10.1002/cjoc.19930110505

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

年代:1993

数据来源: WILEY

摘要:

AbstractA series of tetranuclear Mo(W)‐Ag mixed‐metal clusters have been synthesized by making use of the solid state reactions of [NH4]2[MYS3](M= Mo, W; Y= O, S), AgX(X= Cl, Br, I) and (n‐Bu)4NX' (X' =Cl, Br), two of which [(n‐Bu)4N]3[MoOS3Ag3Br4] (1) and [(n‐Bu)4N]3[WS4Ag3Cl4] (2) have been structurally characterized by X‐ray analysis. The crystal data:1, cubic,P43m, αequals;12.093(4) Å,Z=1,R=0.076;2, cubic,P43m, αequals;12.059(2) Å,Z=1,R=0.075. The cluster anion core [Ag3MS3X'] of the two compounds can be viewed as a cube in which the four metal atoms and the four non‐metal atoms are statistically distributed, respectively. Substitution reaction with PPh3ligand is also discussed for this type of tetr

ISSN:1001-604X    

DOI:10.1002/cjoc.19930110506

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

年代:1993

数据来源: WILEY

摘要:

AbstractSingle crystal Ba0.6K0.4BiO3was studied by using XPS. The results show that there is no evidence for the presence of Bi5+in single crystal of Ba0.6K0.4BiO3; instead, there is evidence for the presence of mixed valent Bi3+and Bi(3+)‐δ. Moreover, the Ols XPS results suggest the presence of mixed valent O2−and O1−, and the valence band spectrum suggests the high degree of covalency for Bi

ISSN:1001-604X    

DOI:10.1002/cjoc.19930110507

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

年代:1993

数据来源: WILEY

摘要:

AbstractIonomeric networks (IN) with lithium sulfate and salt‐solvating oligo(oxyethylene) chain were synthesized on the purpose of improving the conductivity of single‐Li+−ionic conductors. Li+−ionic conductivity depends considerably on the salt content of the INs although the apparent degree of cross‐linking is fixed in a constant of 10 mol%. As salt content (Li/O value) equals 0.0467, conductivity of the IN containing neither small‐molecular salt nor low molecular weight plasticizer reaches a maximum of 7×10−6S/cm at 25°C. Temperature‐conductivity relationship of the INs shows curved Arrhenius plots, suggesting that the ionic conduction is primarily influenced by segmental motion of the polymer host. In addition, WLF (Williams‐Landel‐Ferry) equation is used to analyze the conductivity data, from which the related WLF para

ISSN:1001-604X    

DOI:10.1002/cjoc.19930110508

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe kinetics of oxidation of thiocarbohydrazide in the free and zinc(II)‐bound states by acid bromate have been studied in aqueous and water‐acetic acid (1:1,V/V) media under varying conditions, both in the absence and presence of added bromide ion. The rates of oxidations show first order kinetics in [bromate] in all the cases, but exhibit different kinetic behaviour in [substrate]and [H+]. Oxidation of TCH in aqueous medium shows zero order in [TCH]and nearly second order in [H+], while oxidation in aqueous acetic acid shows two ranges in [H+]. The rate shows first and fractional order kinetics in [TCH]in the first and second acid ranges. Kinetics observed in the presence of Br−are similar to those observed for oxidation of TCH in second acid range. In addition, the reaction shows fractional order in [Br−]. Oxidation of TCH in Zn(II)‐bound state exhibits first order kinetics in [substrate]and second order in [H+]. Increase in ionic strength of the medium decreases the rate in all the cases. Increase in acetic acid composition of the solvent increases the rate. Mechanisms consistent with the observed results have been considered and the rate laws deduced. The rate limiting steps have been identified and the coefficients of these steps have been calculated at different temperatures. The related activation parameters have also been computed. The validity of the deduced rate laws has also been tested by recalculating the rate constants from them as [TCH]and [H+] a

ISSN:1001-604X    

DOI:10.1002/cjoc.19930110509

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe aldol reaction of the silyl enol ether of cyclopent‐2‐enone with aldehydes is mediated by various Lewis acids.Threoisomers are the major diastereoisomers formed in most cases. A reverse diastereoselectivity was observed when the reaction was mediated by TBAF. The results have been discussed in detail by structure and transition state analy

ISSN:1001-604X    

DOI:10.1002/cjoc.19930110510

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

年代:1993

数据来源: WILEY