摘要:

AbstractBased on theab initio/6–31G* calculation, the potential barrier to internal rotation in molecule H3N‐BH3has been studied by means of PD/LSF atomic charge model and Buckingham(exp‐6–1) energy partition method. The results indicate that the order of the contributions of the components to the total energy barrierΔEis |ΔVed|(electrostatic)>|ΔV| (charge transfer)>|ΔVex| (exchange repulsion)>|ΔVdi| (dispersion). ForΔVesthere are maxima atθ= 30° and 90°, and a saddle atθ= 60°. There are good linear relationships for the total barrierΔE, ΔVexandΔV| with cos3θrespectively, and the same for the dipole moment from PD/LSF model (μPD) and that fromab initiocalculation (

ISSN:1001-604X    

DOI:10.1002/cjoc.19920100501

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

年代:1992

数据来源: WILEY

摘要:

AbstractAn investigation on adsorption of NO on reduced CoMo/A12O3and Ru‐Co‐Mo/Al2O3catalysts has been performed using FT‐IR and MS spectroscopies. IR spectra of NO adsorption showed two bands at 1895 and 1800 cm−1, and NO‐TPD profiles gave rise to several peaks at 353, 423 and 473 K, which are assigned to various Co‐sites on the surface. Compared with Co‐Mo/A12O3, the adsorption rate, binding energy, and amount of NO adsorbed on Ru‐Co‐Mo

ISSN:1001-604X    

DOI:10.1002/cjoc.19920100502

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

年代:1992

数据来源: WILEY

摘要:

AbstractThis paper presents the preparations and characterization of vesicles of four new fluorocarbon amphiphiles with 1,3‐disubstituted glycerol structure in common and different headgroups (OH,1; CO2H,2; quaternary ammonium salt,3; and pyridinium salt,4). These vesicles have higher transition temperature due to the stronger hydrophobic interaction between fluorocarbon chains. Addition of fluorocarbon additives with carboxylic acid or quaternary ammonium salt head group respectively shows different influences on phase behavior of vesicles of2. These results are discussed based on the interaction within headgroup, hydrophobicity and specific mutahydrophobic interaction between fluoro‐ and hydrocarbon cha

ISSN:1001-604X    

DOI:10.1002/cjoc.19920100503

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

年代:1992

数据来源: WILEY

摘要:

AbstractReactions of lanthanoid trichlorides with sodium cyclopentylcyclopentadienyl in THF afford bis(cyclopentylcyclopentadienyl)lanthanoid chloride complexes (C2H9C5H4)2LnCl(THF)n(Ln = Nd, Sm,n= 1; Ln = Er, Yb,n= 0). The compound [Cp'2SmCl(THF)]2(2) (Cp' = cyclopentylcyclopentadienyl) crystallizes from mixed solvent of hexane and THF in monoclinic space groupP21/cwitha= 11.583 (3),b= 23.019(6),c= 8.227 (2) Å, β = 90.26 (2)°,V= 2194 (1)Å2,Dc= 1.59 g / cm3,μ= 28.6 cm−1,F(000) = 1060,Z= 2 (dimers). Its crystal molecule is a dimer with a crystallographic symmetry center. The central metal atom Sm is coordinated to two Cp' rings, two bridging chlorine atoms and one THF forming a distorted trigonal bipyramid. The crystal of [Cp'2ErCl]3(3) belongs to the triclinic space groupP1 witha= 11.264 (2),b= 13.296(5),c= 14.296(6)Å, α = 96.99 (3), β = 112.47(2),γ= 102.78(2)°,V= 1865(1)Å2,De= 1.67 g / cm2,μ= 48.0 cm−1,F(000) = 924,Z= 2 (dimers). The molecule is a dimer consisting of two Cp'2ErCl species bridged by two Cl atoms. The central metal atom Er is coordinated to two Cp' rings and two bridging chlorine atoms forming a pseudotetrahedron. All these complexes are soluble in THF, DME, Et2O, tol

ISSN:1001-604X    

DOI:10.1002/cjoc.19920100504

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

年代:1992

数据来源: WILEY

摘要:

AbstractA simple, rapid, accurate and selective complexometric method is proposed for the determination of mercury(II). Mercury(II) is first complexed with a known excess of EDTA and the surplus EDTA is back‐titrated at pH 5.0–6.0 with lead nitrate, xylenol orange being used as indicator. Hexa hydropyrimidine‐2‐thione (HPT) is then added to displace EDTA from the Hg‐EDTA complex quantitatively and the EDTA released is titrated with lead nitrate. Reproducible and accurate results are obtained for 2–55 mg of mercury, with a relative error of less than 0.5% and standard deviation of les

ISSN:1001-604X    

DOI:10.1002/cjoc.19920100505

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

年代:1992

数据来源: WILEY

摘要:

AbstractThe electrochemiluminescence (ECL) of luminol in aqueous alkaline solution was studied. Trace amounts of chloride showed significant effect on the efficiency of light emission of luminol as a positive trigonometrical wave pulse was exerted on the solution. The detection limit for the chloride is 5.0 × 10−5mol / L and the linear calibration range extends up to 1.0×10−2mol /L; the relative standard deviation for 1.0×10−5mol / L chloride is 5%. The influencing factors for chloride determination are also discussed. The possible mechanism for the electrochemiluminescence reaction may be due to the oxidation of chloride ion in the solution to ClO−, and the latter acts on luminol and then gives out luminescence. The method has been applied to determine the total chloride in tap water with satisfacto

ISSN:1001-604X    

DOI:10.1002/cjoc.19920100506

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

年代:1992

数据来源: WILEY

摘要:

AbstractTerbium‐ and yttrium‐group rare earths form β‐complexes with CPApC in acidic medium. The sensitivities for determination of these rare earths by this reaction depend on their ionic radii. Cerium‐ or terbium‐group rare earth in the presence of yttrium‐group element produces the cocolouration effect which remarkably sensitizes the reaction. Yb‐CPApC‐Eu complex has a molar composition of 1:4:2 and gives a molar absorptivity of 2.02×103L·mol−1·cm−1at 746 nm for Eu. It is found that the closer the lengths of ionic radii of the rare earths are, the greater will be t

ISSN:1001-604X    

DOI:10.1002/cjoc.19920100507

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

年代:1992

数据来源: WILEY

摘要:

AbstractSix chiral diamide stationary phases (CSPs), namelyN‐(3‐carbobenzoxypropionyl)‐L‐Val‐tert‐butylamide (CSP‐1),N‐undecenoyl‐L‐Val‐S‐α‐phenylethylamide (CSP‐2),N‐undecenoyl‐L‐Val‐R‐α‐phenylethylamide (CSP‐3), OV‐225‐L‐Val‐tert‐butylamide (CSP‐4), XE‐60‐L‐Val‐tert‐butylamide (CSP‐5) and polycyanoethyl vinyl siloxane‐L‐Val‐tert‐butylamide (CSP‐6), were investigated and CSP‐6 was crosslinked within narrow bore (70μm) fused silica capillary columns. The separation of amino acid

ISSN:1001-604X    

DOI:10.1002/cjoc.19920100508

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

年代:1992

数据来源: WILEY

摘要:

AbstractAsymmetric syntheses of (S)‐α‐amino acids in 28–98% optical yields via double chiral induction in alkylations of ketimine 1 derived from (+)‐2‐hydroxypinan‐3‐one and (‐)‐menthyl glycinate which is a chiral match pair have been studied. The factors controlling the diastereoselectivities in alkylation reactions of the ketimine, the properties of alkylating agents and various alkylation condi

ISSN:1001-604X    

DOI:10.1002/cjoc.19920100509

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

年代:1992

数据来源: WILEY

摘要:

AbstractAddition of various polyfluoroalkyl halides including 1,2‐dihalopolyfluoroalkanes to 1‐octene is effected by using a catalytic amount of Cp2TiCl3(IV) and iron powder to give 1:1 adducts in excellent yields. The reaction is performed in EtOH or THF. A Cp2TiCl(III) mediated radical mechanism is proposed. Radical reactivity of polyfluoroalkanes toward 1‐octene was found to be ‐CF2I>‐CF2Br

ISSN:1001-604X    

DOI:10.1002/cjoc.19920100510

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

年代:1992

数据来源: WILEY