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71.
Heating a toluene solution of dicarhomethoxyacetylenebis(triphenylphosphine)platinum(0) at 130°C gives the ortho-metalated complex (Ph3P)(Ph2t-trans-(COOMe)CCHCOOMe. 相似文献
72.
A solid-phase extraction method is described for the separation of alachlor, atrazine and metolachlor from groundwater using solid-phase disposable columns. The method is rapid, reproducible and uses considerably fewer reagents than classical liquid-liquid methods. The average recoveries were greater than 90% for all three compounds. 相似文献
73.
The reaction of a racemic perhydroisoquinolene derivative 9 with the homochiral lithium amide basse 3 in the presence of Me3SiCl in an regiodivergent fashion to give the two non-racemic regioisomeric enol silanes 10 and 11. Conversion of 10 into enone 15, an intermediate useful in the synthesis of the alkaloid (+)-yohimbine, was also possible. 相似文献
74.
D. T. Clark M. Z. Abrahman 《Journal of polymer science. Part A, Polymer chemistry》1981,19(11):2689-2703
A systematic investigation has been made of the composition, gross structural features, and rates of deposition of plasma polymer films produced from the excitation of inductively coupled RF plasmas in the isomeric tetrafluorobenzenes. ESCA data reveal that the dominant reaction involves rearrangement such that under a wide variety of experimental conditions the composition of the crosslinked products remains essentially the same as that of the starting material. Small differences in rates of deposition are observed for the different isomers, and theoretical SCF MO studies at the MNDO level provides a basis for discussion of the experimental data. 相似文献
75.
D. T. Clark B. J. Cromarty A. Dilks 《Journal of polymer science. Part A, Polymer chemistry》1978,16(12):3173-3184
Nonempirical LCAO MO SCF computations (in the ΔSCF formalism) have been carried out of binding energies and relaxation energies for an extensive series of oxygen-containing organic systems encompassing most of the common functionalities. The molecules for which experimental data are available for comparison demonstrate the adequacy of the treatment for describing the relative binding energies for both the Cls and Ols core levels. A sound basis is therefore provided for the discussion of relative core binding energies (Cls and Ols) for functionalities for which experimental data are not available, that is, hydroperoxides, peroxides, peroxyacids, and peroxyesters, a knowledge of which is essential for investigations of the surface oxidation of polymers by means of ESCA. Cls shifts are discussed in terms of primary and secondary substituent effects of oxygen, which greatly simplify the analysis of complex unresolved spectra, whereas for the Ols levels a similar but less straightforward situation exists. The relaxation energies associated with both Cls and Ols core ionization follow a dependence on the binding energy for a given structural type. 相似文献
76.
77.
W.John Albery David Clark Humphrey J.J. Drummond Anthony J.M. Coombs William K. Young Clive E.W. Hahn 《Journal of Electroanalytical Chemistry》1992,340(1-2)
A novel electrochemical sensor for the determination of CO2 in expired breath is described. The sensor works by generating
from the reduction of O2 in dimethyl sulphoxide (DMSO) in a generating pulse. There is a rapid titration reaction between the
and any CO2 present. In the recovery pulse the amount of unreacted
is determined. The larger the concentration of CO2 the less
is found in the recovery pulse. The solubilities and diffusion coefficients of O2 and CO2 in DMSO have been determined using rotating disc voltammetry and rotation speed step experiments. The stoichiometry, the product, and the rate constant of the titration reaction have been determined using ring—disc voltammetry and laser Raman spectroscopy. The operation and the effect of adventitious water on the sensor are described. Results are presented which show that the sensor can indeed measure the breath-by-breath rhythm of expired CO2 from a human subject. 相似文献
78.
Clark GR Pytel PD Squire CJ Neidle S 《Journal of the American Chemical Society》2003,125(14):4066-4067
The first crystal structure of a drug (daunomycin) bound to a parallel-stranded intermolecular telomeric G4 quadruplex (d(TGGGGT)4) has been determined to high resolution. A planar assemblage of three daunomycin molecules stacks onto the 5' end of the G4 column, with the daunosamine substituents occupying three of the four quadruplex grooves. The surface area of the terminal G-quartet in this parallel DNA quadruplex, presently occupied by three daunomycins, is sufficiently large that it could easily accommodate other potential telomerase inhibitors such as substituted porphyrins or telomestatin. 相似文献
79.
We have investigated the transitions between disordered phases in supercooled liquid silicon using computer simulations. The thermodynamic properties were directly obtained from the free energy, which was computed using the recently proposed reversible scaling method. The calculated free energies of the crystalline and liquid phases of silicon at zero pressure, obtained using the environment dependent interatomic potential, are in excellent agreement with the available experimental data. The results show that, at zero pressure, a weak first-order liquid-liquid transition occurs at 1135 K and a continuous liquid-amorphous transition takes place at 843 K. These results are consistent with the existence of a second critical point for the liquid-liquid transition at a negative pressure. 相似文献
80.
The source of the effect of N-alkylation on the redox properties of Ni(II/I) and Cr(III/II) cyclam complexes has been investigated using DFT calculations. The structures of the anhydrous and hydrated complexes were optimized in the gas phase, and single point calculations were performed in a polarized continuum. The main results are the following: the decrease in outer sphere solvation upon N-alkylation is the major source of the relative stabilization of the lower oxidation state complexes by the tertiary amine ligands; tertiary amine nitrogen donors are stronger sigma-donors than the secondary amines, as predicted from the inductive effect of alkyls; steric strain elongates the metal-nitrogen bonds in the tertiary complexes and decreases the ligand strain energies; and the site of water binding to the complexes differs because of their different electronic structures (i.e., in the Ni complexes, the water molecules bind to the M[bond]N[bond]H sites, whereas in the Cr complexes they bind to the central metal cation). Outer sphere hydrogen bonding of water to the ligands in the coordination sphere lowers the ionization potentials by charge delocalization. 相似文献