摘要:

AbstractFor the isomerization reaction of monofluoro‐disilene, the geometrical structures of reactant, product and transition state have been optimized and energy constant, vibrational frequency calculated. By means of the statistical thermodynamics and Eyring's transition state theory, the equilibrium constant, rate constant and heat of isomerization have also been computed. Hence, this reaction has been analysed completel

ISSN:1001-604X    

DOI:10.1002/cjoc.19900080302

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractIn this paper, INDO perturbation theory has been extended to calculate the NMR chemical shifts of transition metal compounds. The nitrogen and oxygen INDO parameters have been refined by using a set of nitrogen and oxygen containing compounds to minimize the differences between calculated and experimental13C,15N, and17O shielding constants. These refined parameters, together with optimally selected iron INDO parameters, were used to evaluate the13C chemical shifts of three iron complexes (C5H5)Fe(CO)2CN, (C5H4CHO)2Fe2, and (C5H4CH2OH)2Fe. The calculated13C,15N and17O shielding constants were fairly in agreement with experimental results. In addition, a good linear relationship between the calculated [diamagnetic shielding constants σd(M) of13C,15N and17O nuclei and the net charge ρ (M) of these atoms was notice

ISSN:1001-604X    

DOI:10.1002/cjoc.19900080303

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractTungsten oxycarbide with specific surface area ⋍ 24 m2/g was prepared from white tungstic acid by reduction and carburization with CO and H2. XRD and EXAFS measurements confirmed that the WOC obtained has a simple hexagonal structure isotypic with α‐WC and the oxygen is inserted into the trigonal prismatic interstices of the crystal lattice. The reactions ofn‐hexane,n‐heptane and cyclohexane on WOC were studied and compared with WC prepared by direct synthesis at high temperature. WOC and WC are active for the hydrogenolysis, isomerization and dehydrocyclization of alkanes and dehydrogenation of cyclohexane and their catalytic properties are in many ways similar to Pt catalysts. Oxygen insertion inhibits the catalytic activities of tungsten carbide for hydrocarbon conversion reactions probably due to electroni

ISSN:1001-604X    

DOI:10.1002/cjoc.19900080304

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractThe unimolecular reactions of silathione: (a) dehydrogenation, (b)trans‐isomerization, (c)cis‐isomerization, are investigated byab initioMO calculations using RHF/4‐31G basis set. The geometries and energies of the reactant, transition states and products have been determined on the singlet potential energy surface of the ground state. The reaction ergodography along the intrinsic reaction coordinate (IRC) for the three reactions has also been perf

ISSN:1001-604X    

DOI:10.1002/cjoc.19900080305

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractTheab initiocalculations have been performed on the reaction paths of 1,2‐H shift and inversion processes of amino‐carbene molecule by the Intrinsic Reaction Coordinate (IRC) method. We have determined the equilibrium geometries and energies of the reactant, transition state and product, and obtained the activation energies, reaction heats, frequency factors and the activation entropies of these two reaction processes. The vibrational correlation from reactant to transition state indicated that the IRCs of 1,2‐H shift and inversion processes were associated with the deformation modes of 1540 and 1208 cm−1, respectively. The vibrational coupling between normal coordinates in the inversion process would be helpful for selecting the inversion reaction

ISSN:1001-604X    

DOI:10.1002/cjoc.19900080306

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractThree empirical rules of interfacial potential and Gibb's energy with the radius, charge number of transfer ions and dielectric constant of organic phase are obtained for the ion transfer across the liquid‐liquid interface, which are verified by the transfer of simple anions, dye ions and metal ions facilitated by neutral ionophores across the interface between water and some organic solvents, and deduced theoretically based on the electrostatic interaction of ion and high‐permittivity solvent. The rules are proved to be effective of choosing supporting electrolytes and searching for new transfer system which follows the rule thatr/nof transfer ion should be larger than that of electrolytes ion in water phase and less than that in organic phase. A rule for judgement of the charge sign of transfer ion is suggested firstly based on the relationship between interfacial half‐wave potential and dielectric constant of organic

ISSN:1001-604X    

DOI:10.1002/cjoc.19900080307

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractFive samples of chemically desposited Ni‐P amorphous alloys were prepared and investigated. In these amorphous alloys there are Ni‐P atom groups in which phosphorus and nickel are connected with strong interaction. Nickel atoms and Ni‐P groups are deposited in a random manner on the surface of matrix and a quasilayer structure is formed. The spacing between two layers in alloys resembles that in (111) plane in the nickel crystal. Therefore there is a peak at the same position of 2θ=44.4° as that of the (111) reflection of crystalline nickel in the X‐ray powder diffraction pattern of alloys. However, the dimension of Ni‐P groups is different from that of a nickel atom and the atomic arrangement in the layer is in disorder. These result in the space change and there is a distribution of spacing around the average. As a consequence of distribution of spacings, the peak at 2θ=44.4° is broadened and enhanced as the amount o

ISSN:1001-604X    

DOI:10.1002/cjoc.19900080308

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractTwo‐dimensional NMR study on the single‐stranded octadeoxynucleotide, d(TT‐GGGGTT) is presented. Assignments of the base protons, the H1′, H2′ and H2″ protons were made by two‐dimensional Nuclear Overhauser Enhancement Spectroscopy (NOESY) and two‐dimensional homonuclear J‐correlated Spectroscopy (COSY). The result indicates that the overall structure of the single‐stranded d (TTGGGGTT) is a right

ISSN:1001-604X    

DOI:10.1002/cjoc.19900080309

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractThe complete amino acid sequence of chicken plasma apolipoprotein (apo) A‐I was determined by sequencing overlapping peptide fragments produced by trypsin, S. aureus V8 protease, and cyanogen bromide cleavage respectively. All of the peptide fragments were purified on a Waters or on a Beckman HPLC system with a Vydac C18column using 0.1% TFA in water as buffer A, and 0.08% TFA in 95% acetonitrile and 5% water as buffer B. Most of the peaks separated by these systems were pure. The partially purified fractions were subjected to rechromatography with a Hypersil ODS column using 0.005M sodium phosphate, pH 6.0, as buffer A, and 90% acetonitrile and 10% water as buffer B. The N‐terminus of chicken apo A‐I was determined to be aspartic acid by directly sequencing the intact protein up to 30 residues, while the C‐terminus was identified as alanine by carboxypeptidase Y cleavage. There are 240 amino acid residues in mature chicken apo A‐I. By direct analysis of cyanogen bromide peptide, we also determined the sequence of a 6 amino acid prosegment, which is present at approximately 10% of the molar amount of the mature protein in chick

ISSN:1001-604X    

DOI:10.1002/cjoc.19900080310

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractReaction of aqueous solution of sodium perfluoroalkanesulfinate with cupric sulphate gave a high yield of cupric perfluoroalkanesulfinate, which decomposed slowly in the air on exposure to light to give perfluorocarboxylic acid. The reaction between cupric perfluoroalkanesulfinate and olefins in the presence of potassium iodide and excess CuSO4in ether at low temperature (‐30 to‐20°C) formed two kinds of adducts, namely the normal adducts, RfSO2CH2CHIR(2) and the adducts resulting from the loss of SO2moiety, RfCH2CHIR(3) in yields ranging from morderate to good. These results were identical with that of the addition of perfluoroalkanesulfonyl iodide to olefins. A radical reaction mechanism is prop

ISSN:1001-604X    

DOI:10.1002/cjoc.19900080311

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY