摘要:

AbstractAccording to geometrical considerations, a method is devised to show a geometric relationship between the tetrahedron and the small heterofullerenes below C60: C24N4, C36N4and C52N4all of which belong to the Tdpoint group. These simple geometric relationships also allow us to predict the possible structures of heterofullerenes consisting of more than sixty carbons with the Tdsymmetry. The number of hexagonal faces (besides the 12 pentagonal faces), vertices and edges of these heterofullerenes are obtained by applying Euler's theorem. Calculated by means of molecular mechanics MM2(87), the minimum energy structure, the bond lengths, the bond angles and the torsion angles for such heterofullerenes were generated. The simple Hückel MO calculations are used to determine the HOMO, LUMO and the energy gap between HOMO and LUMO of C24N4and C36N4heterofullerenes. The heats of formation of C28and C40, C24N4and C36N4were calculated according to the MNDO method. The ionization energies, die Δϵ (LUMO‐HOMO) and the resonance energies were investigated with semiempirical MNDO methods for comparison with the stabilities of C28, C24N4and C28H4. The kinetic and thermodynamic stabilities of such tetrahedral derivatives of heterofullerenes were predicted based on the energy gaps and heats of forma

ISSN:0009-4536    

DOI:10.1002/jccs.199300080

出版商:WILEY‐VCH Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractThe intermediates of nitrene‐extrusion reaction were found in the forms of (ANB)Fe(CO)4or (ANB)Fe(CO)3during the reaction of 7‐azanorbornadiene derivatives (ANB) with diiron nonacarbonyl. By using extended Hückel molecular orbital (EHMO) calculation, we found that the chemical behavior of these complexes is correlated with the nature of substituents of ANB. The relative reactivity of (ANB)Fe(CO)4and (ANB)Fe(CO)3is influenced by the charge distributions on iron and nitrogen. In the crystal structure of (ANB)Fe(CO)4an angular distortion of Fc‐C=O is observed, which is a result of donor‐acceptor interaction between the lone‐pair of N and the π* or

ISSN:0009-4536    

DOI:10.1002/jccs.199300081

出版商:WILEY‐VCH Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractThe catalytic properties of Na‐buserite and Keggin ion‐pillared buserite (abbreviated as KPB) in the oxidation of ethane, were investigated with varied mixtures of ethane and air. Na‐buserite Na4Mn14O26xH2O is a layered manganese oxide, KPB was prepared by the introduction of aluminium Keggin ions, [Al13O4(OH)24(H2O)12]7+into the interlayers. Pillaring of the interlayers increases the active surface area participating in the reactions, as indicated by greater conversion over KPB than over a Na‐buserite catalyst. In an oxygen‐rich environment, complete combustion of ethane is achieved at temperatures ≈︁ 350 °C over KPB, and the structure of KPB is retained. The structure of KPB is less stable than that of Na‐buserite in an oxygen‐poor environment, and it disintegrates at large conversion. This phenomenon is explained in terms of the oxygen deficiency in the interlayer at a large reaction rate. Similar effects were absent from an oxygen‐rich environment. The variation of the product selectivity of Na‐buserite and KPB catalysts is discussed in terms of the presence of int

ISSN:0009-4536    

DOI:10.1002/jccs.199300082

出版商:WILEY‐VCH Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractSupercritical extraction with CO2as solvent was adopted to remove alkaloids and safrole from the betel quid. The extraction efficiency was significantly affected by the operating pressure and temperature. Results of sensory evaluation showed that the eating qualities of the betel quid decreased but still satisfied the chewer after the extraction treatment.

ISSN:0009-4536    

DOI:10.1002/jccs.199300083

出版商:WILEY‐VCH Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractThe molecular structure of a binuclear copper(II) complex [Cu2L2DMF2]·DMF·2ClO4in which LH is 4‐methyl‐2,6‐bis (indazol‐2‐ylmethyl)phenol and DMF isN,N‐dimethylformamide is reported. The structure of the crystal was characterized by X‐ray diffraction: monoclinic, space group P21/C, Z = 2, a = 15.863(4), b = 20.642(3),c = 19.598(5) Å, β = 113.05(2)°. The final R and Rw values are 0.060 and 0.061, respectively, for 4777 reflections with I>2σ(I). Each copper(II) is penta coordinate, with two N atoms from the indazole ring, two O atoms from phenolate in ligands and another O atom from DMF to form a distorted square‐pyramid. The mean value of the lengths of the four Cu‐N bonds is 1.987(6) Å and the Cu ⃛Cu distance is 3.094(1) Å No EPR signal was detected, and the magnetic moment has a small value μ = 1.17 per copper. These results indicate strong antiferromagnetic interaction bet

ISSN:0009-4536    

DOI:10.1002/jccs.199300084

出版商:WILEY‐VCH Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractThe title complex underwent ligand substitution by diphenylphosphine to form dicarbonyl[P,P′,S‐(2,2‐bis(diphenylphosphinoniethyl)‐1‐phcnylthiopropane](diphenylphospline)manganesc(I) hexafluorophosphate 2 under photochemical conditions. The crystal structure of complex 2 was determined. The reaction was kinetically independent of the concentration of diphenylphosphine, so a first‐ord

ISSN:0009-4536    

DOI:10.1002/jccs.199300085

出版商:WILEY‐VCH Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractExtended fluorescence quenching analysis is demonstrated to be an efficient steady‐state method to evaluate the exciplex (excimer) rate constants under certain conditions. This method is attractive as the monitor of only fluorescence of the exciplex's precursor is required for a complete analysis, regardless whether or not the exciplex. Using the interaction of methyl 2‐naphlhoate in its singlet excited state with H2S04as a kinetic model, for which all the rate constants are known, this method is described and shown to reproduce accurately these rate constants. Limitations and applications of this method are discus

ISSN:0009-4536    

DOI:10.1002/jccs.199300086

出版商:WILEY‐VCH Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractPhotochemical reactions of 2‐cyclopentylidenecyclopentanone with diisopropylmethylamine, diisopropylethylamine, dimethylaniline, triethylamine, isopropyldimethylamine and dimethylbutylamine in acetonitrile were studied. Besides the addition product, a novel 3+2 cycloaddition adduct 3a‐hydroxytrispiro(octahydropentalene‐1,1′:2,1″:3,1‴‐triscyclopentane)‐2‴‐one was isolated. The quantum yield and Stern‐Volmer parameters with triplet quencher piperylene are reported. From these kinetic studies of mechanism photo‐induced electron transfer and proton transfer is proposed for formation of the novel 3+2 cycloadduct of 2‐cyclo

ISSN:0009-4536    

DOI:10.1002/jccs.199300087

出版商:WILEY‐VCH Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractIrradiation of bicyclo[2.2.2]oct‐5‐ene‐2,3‐diones la‐c proceeded quantitatively via 1,3‐acyl shifts to yield the corresponding bicyclo[4.2.0]oct‐2‐ene‐7,8‐diones 2a‐c that underwent bisdecarbonylation to afford also quantitatively 1,3‐cyclohexadienes 3a‐c upon further excitation. In contrast the thermolysis of 2c produced lc and 4; the kinetic parameters were found to be ΔH≠= (90.4 ± 0.8) kJ mot.1and

ISSN:0009-4536    

DOI:10.1002/jccs.199300088

出版商:WILEY‐VCH Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractA systematic investigation of the electrochemical reduction of substituted anthracenes inN,N‐dimethylformamidc has unveiled the reductive properties of the aromatic compounds. For the anthracenes with a reversible first reduction, the redox potential exhibits linearity vs a value of the Hammett equation. For anthracenes with an irreversible first reduction, the electron transfer and chemical reaction occur via either a sequential or a concerted pathway. When the irreversible first reduction occurs at a potential more negative than E1/2calculated from the σ value, the reaction occurs via a sequential pathway, such as for 9‐chloroanthracene. When the irreversible first reduction occurs at a potential more positive than the expected E1/2, the reaction occurs via a concerted mechanism of electron transfer and bond breaking, such as for 9‐chloromethylanthracenc. The displacement of the halide results in the parent polyaromatic hydrocarbons, as in dicated by the spectroelectrochemical

ISSN:0009-4536    

DOI:10.1002/jccs.199300089

出版商:WILEY‐VCH Verlag    

年代:1993

数据来源: WILEY