摘要:

AbstractThe bonding nature of the canonical molecular orbitals 2σg, 2σu and 3σg in the molecules N2,O2, F2and the related analogous molecular orbitals in the molecules P2and CO, is analysed using Weinhold's natural bond orbital set. When the canonical molecular orbitals can be well localized into natural bond orbitals, the covalent bond can be completely attributed to the bonding type natural bond orbitals. The decomposition of canonical molecular orbitals into the natural bond orbital basis then gives the weighted bond order as the component of the bonding portion in the canonical molecular orbital. The weighted bond order results match the photoelectron spectroscopy assignment quite satisfactori

ISSN:0009-4536    

DOI:10.1002/jccs.199600001

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractA charge distribution method to solve the linearized Poisson‐Boltzmann equation numerically through use of the finite difference method is proposed, The molecules are mapped by 1 and 0.25 Å grid systems. Each atom is modeled as a point charge and a weighted sum of point charge of every atom that is within its van der Waals radius with a grid point is assigned to the grid point. Depending on a charge distribution factor determined, the charge/grid (q/g) ratio calculated for every grid point inside a molecule can be fixed to a certain value. A grid size of the I Å grid is often fixed for mapping a small or large molecular system. Solvation energies for a group of small molecules calculated by the method arc comparable with those calculated by other methods and the grid energy calculated by the method is also redu

ISSN:0009-4536    

DOI:10.1002/jccs.199600002

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractTwo kinds of capillary columns were prepared and tested as the stationary phases of ligand exchange gas chromatographic separation of dialkyl sulfides. The PTFE column wall‐coated with silane‐DTC‐Cu but without the addition of silicone exhibits significantly better selectivity towards dialkyl sulfides than a column wall‐coated with 10% silane‐DTC‐Cu in silicone. With the first column connected to a microsample injection valve and a microsample loop, the quantitative determination of dialkyl sulfides can be performed. The column also shows great promise for the separation of dialkyl sulfide‐hydroca

ISSN:0009-4536    

DOI:10.1002/jccs.199600003

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractA variety of chlorinated organic wastes were photodecomposed with p‐CuO‐modified TiO2particles (denoted CuO/TiO2). Based on the photoactivity measured in oxygenated solutions containing sodium 2,2′‐dichloropropionate, the photoactivity of TiO2is significantly enhanced with p‐CuO loading; in the case with 0.4 wt% of CuO, the activity is increased by a facor of 4. Photochemical‐TiO2‐slurry cell techniques and voltammetric characterizations suggest this CuO‐promoted enhancement is likely to result from the acceleration of oxygen reduction at TiO2via CuIIO/CuI0. Long‐term tests showed that these CuO/TiO2particles are photochemically robust; within 100‐hours' continuous photolysis, insignificant loss in photoactivity was detected. However, increasing loading of p‐CuO may jeopardize the photoactivity, due to the deterioration in the TiO2absorbabil

ISSN:0009-4536    

DOI:10.1002/jccs.199600004

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThecis‐[Mn(CO)4(TePh)2]−, similar to bidentate ligand PhTe(CH2)3TePh, acts as a “chelating metalloligand” for the synthesis of metallic tellurolate compounds. The reaction ofcis[Mn(CO)4(TePh)2]−with BrMn(CO)5in THF leads to a mixture of products[(CO)3,BrMn(μ‐TePh)2Mn(CO)4]−(1) and Mn2(μ‐TePh)2(CO)g(2). Complex 1 crystallizes in the triclinic space group Pl̄ with a = 11.309(3) Å,b= 14.780(5) Å, c = 19.212(6) Å, a = 76.05(3)° β = 72.31(3)°, γ = 70.41(3)° V = 2848(2) Å3, Z = 2. Final R = 0.034 and Rw= 0.035 resulting from refinement of 10021 total reflections with 677 parameters, Dropwise addition of (MeTe)2to a solution of [Me3O][BF4] in CH3CN leads to formation of [Me2TeTeMe][BF4], a potential MeTe+donor ligand. In contrast to oxidative addition of diphenyl ditelluride to [Mn(CO)s]−to givecis‐[Mn(CO)4(TePh)2]−which was thermally transformed into [(CO)3Mn(μ‐TePh)3Mn(CO)3]−, reaction of [Mn(CO)5]−with [Me2TeTeMe]+proceeded to give the monomeric species MeTeMn(CO)5as initial product which was

ISSN:0009-4536    

DOI:10.1002/jccs.199600005

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractRedox reactions of Co(edta)−with Ru(NH3)5L2+(L = 3‐ and 4‐aminopyridine (AmPy)) were found to follow an outer‐sphere electron transfer mechanism. The specific rate constants are (3.26 ± 0.03) × 102and (3.07 ± 0.04) × 103M−1S−1, for L = 3‐ and 4‐AmPy, respectively, at μ, = 0.10 M LiClO4, pH = 8.0 (tris) and T = 25 °C. The rate constants of oxidations for a series of Ru(NH3)5L2+complexes are higher than those of the corresponding Fe(CN)5L3‐complexes by factors of 4 to 15 even after corrections for differences in reduction potentials and in charges of the complexes. Nonadiabaticity in the reactions of Fe(CN)5L3 complexes may account for the difference in th

ISSN:0009-4536    

DOI:10.1002/jccs.199600006

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractMethyl 3‐amino‐2‐methoxy‐7‐isopropylazulene‐l‐carboxylate(8a) and its 5‐isopropyl isomer (8b) were synthesized by reduction of the 3‐nitro derivatives (7a,b) with zinc/acetic acid in excellent yields.7aand7bwere prepared by nitration and methylation of methyl 7‐isopropyl‐2‐hydroxyazulene‐l‐carboxylate (5a) and methyl 5‐isopropyl‐2‐hydroxyazulene‐l‐carboxylate (5b), respectively. Diazotization of8awith sodium nitrite in trifluoroacetic acid at 0 °C gave methyl 5‐isopropyl‐1,2‐azulenequinone‐3‐carboxylate (9a) in 91% yield. Similar reaction of8bgave the corresponding methyl 7‐isopropyl‐1,2‐azulenequinone‐3‐carboxylate (9b) in 93% yield. No evidence for

ISSN:0009-4536    

DOI:10.1002/jccs.199600007

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThe separation of amino acids into enantiomers while derivatizing with benzoyl chlorides is demonstrated. It was found that enantioselectivity among these reagents tagging with the same amino acid is quite different and is very sensitive to its structural variations. A noninclusion complexation mechanismi.e. external association is thought to involve in the separation carried out with a nonaqueous polar organic mobile phase. Results also indicate that the chiral recognition seems to be controlled either by moieties from tagging reagents or functional groups on all amino acids examined in this study on the basis of competition. The polarity of side‐chain group on peptide backbone can not be ignored in achieving a successful separation. Furthermore, chiral recognition appears to closely rely upon the location of stereogenic center that is simultaneously attached by amino and carboxyl groups. Finally, mechanism involved will be explored structurally with these tagging reagents derivatized amino acids which structures are highly ordered and amine‐containing compounds with structures similar to that of amino a

ISSN:0009-4536    

DOI:10.1002/jccs.199600008

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractTreatment of 3‐phenylthio‐2‐sulfolene (1) with an equimolar proportion of butyllithium at −78 °C in THF followed by addition of an electrophile gave the 2‐substituted 3‐phenylthio‐2‐sulfolenes (2). The deprotonation was found to proceed only at the vinylic C‐2 position. Some of the 2‐sulfolenes 2 underwent desulfonylation upon heating with base. Of particular interest was the conversion of 3‐phenylthio‐2‐trimethylsilyl‐2‐sulfolene (2h) to its 3‐sulfolene isomer6by sequential addition of butyllithium and salicylic acid at low temperatures. The 3‐sulfolene6was desulfonylated by Kugelrohr distillation at 150° C under vacuum to give (Z)‐2‐phenylthio‐l‐trimethylsilyl‐1,3‐butadiene (8). The regiochemistry of the Diels Alder reaction of this highly reactive diene8was found to be controlled by the phenylthio group, and the stereochemistry isendoaddition. Diene8was oxidized to its sulfone derivative12which also

ISSN:0009-4536    

DOI:10.1002/jccs.199600009

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractAddition of hydrochloric or hydrobromic acid to a solution of potassium permanganate in acetonitrile produced a homogeneous mixture, which is suitable for laboratory chlorination or bromination, respectively. Aromatic compounds more reactive than alkylbenzenes can be chlorinated or brominated without additional catalyst. Alkenes and alkynes give the correspondingvicinaldihaloalkanes and vinyl halides. All reactions complete within two hours under mild condition (25‐60 °C) with excellent to moderate yiel

ISSN:0009-4536    

DOI:10.1002/jccs.199600010

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY