Some cationic five coordinate complexes of formula [Os(CO)(NO)L2A]PF6 (L = tertiary phosphine, A = an acetylene) have been prepared by reaction of the appropriate acetylene with [Os(CO)(NO)L2(acetone)]PF6; the variable temperature 1H NMR spectra of some of these indicate that the coordinated π-acetylene undergoes fluxional behaviour. 相似文献
Using a method developed by us, a non-isothermal kinetic study of the thermal decomposition of some coordination compounds (CC) with the general formula MeIILpX2, where , was performed. 相似文献
The results of a kinetic investigation of the non-isothermal degradation and the isothermal degradation of the residual deformation
under constant deflection for polychloroprene rubber are presented. A relationship was derived between the degree of non-isothermal
conversion and the value of the investigated mechanical property.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
Nucleotides. XV. Synthesis and Properties of 2′O-t-Butyldimethylsilyl-5′-O-monomethoxytritylribonucleoside-3′-phosphotriesters, Starting Materials for Oligonucleotide Syntheses The syntheses of two types of fully blocked ribonucleoside 3′-phosphotriesters 6–14 have been achieved in excellent yields from 2′-O-t-butyldimethylsilyl-5′-O-monomethoxytrityl-ribonucleosides 1–5 by phosphorylation with 2-chloro- and 2,5-dichlorophenylphosphorodichloridate respectively and subsequent treatment by cyanoethanol to 6 , 8 , 10 , 12 and 14 and by p-nitrophenylethanol to 7 , 9 , 11 and 13 . These phosphotriesters are valuable starting materials for oligonucleotide syntheses due to the fact that the corresponding phosphotriesters 15–23 with free HO? C(5′) could be obtained by detritylation and the 3′-phosphodiester triethylammonium salts 24–32 by deblocking of the cyanoethyl and the 2,5-dichlorophenyl group respectively. All newly synthesized compounds have been characterized by UV.-and NMR.-spectra as well as C, H, N elementary analyses. 相似文献
We show that the kinetic model of a single rate-determining step in a reaction mechanism can be extended to systems with multiple overall reactions for which the elementary reactions obey nonideal or fractal kinetics. The following assumptions are necessary: (1) The system studied is either closed or open, but no constraints exist preventing the evolution toward equilibrium. (2) Elementary reactions occur in pairs of forward and backward steps. (3) The kinetics of the elementary steps are either nonideal or fractal and are compatible with equilibrium thermodynamics. (4) The number of reaction routes is identical with the number of rate-determining steps. If these hypotheses are valid, then the overall reaction rates can be explicitly evaluated: they have a form similar to the kinetic equations for the elementary reactions and the apparent reaction orders and fractal coefficients can be expressed analytically in terms of the kinetic parameters of the elementary reactions. We derive a set of relationships which connect the equilibrium constants of the reaction routes, the corresponding overall rate coefficients, and the stoichiometric numbers of the rate-determining steps. We also derive a set of generalized Boreskov relations among the apparent activation energies of the forward and backward overall processes, the corresponding reaction enthalpies, and the stoichiometric coefficients of the rate-determining steps. If the elementary reactions obey fractal kinetics, the same is true for the rate-determining steps. The fractal exponents of the forward and backward overall reactions are linear combinations of the fractal exponents of the fractal elementary reactions. Similar to the theory of single rate-determining steps, our approach can be used for selecting suitable reaction mechanisms from experimental data. 相似文献
The stoichiometry and spectral properties of [Ni(4-Etpy)4(NCS)2]nG clathrates have been studied where n = 2 for G = 1-BrN (N = naphthalene), n = 1 or 2 for G = 1-MeN, and n = 0.5 for 2-MeN and 2-BrN. The complexes under study show electronic absorption spectra typical of an octahedral environment of the Ni(II) central atom. The differences found in IR spectra for the (CN) and (Ni–-NNCS) vibrations are discussed. The crystal structure of [Ni(4-Etpy)4(NCS)2]1-MeN was determined by X-ray diffraction and refined to R = 0.0586. Discrete non-centrosymmetric [Ni(4-Etpy)4(NCS)2] molecules form layers of a host structure and the space between the layers is occupied by 1-MeN. The relationship between interatomic distances in the host complex of similar clathrates are discussed. 相似文献
Trimethylsilyl ethers of various hydroxyl-containing thiazole derivatives have been synthesized. The psychotropic activity (in vivo) and the cytotoxicity (in vitro on tumor cell lines HT-1080 and MG-22A) of these ethers and of their unsilylated precursors have been studied. It was discovered that the obtained compounds possess a sedative action. A moderate cytotoxic effect was detected for piperidine-containing thiazoles, displayed most strongly in relation to MG-22A cells. 相似文献
The dehydration of a series of VPI-5 and H3 samples, synthesized under various conditions, as well as the solid state transformation
of VPI-5 to AlPO4-8 have been investigated using combined TG-DTG-DSC and high-resolution solid state31P-NMR. The TG curves show a quasi-continuous release of water, the total loss being characteristic for each sample. Complete
dehydration is achieved when the samples are heated from 20°C to about 150°C at various beating rates. Besides the main dehydration
effect, several weak endothermic peaks are observed. These generally non-reproducible modulated peaks, recorded at high heating
rates, are presumably due to the interactions of the water molecules leaving the channels of VPI-5 with the randomly positioned
fragments stemming from the destruction of the water triple helix assemblage.
The non-isothermal kinetic parameters of the dehydration have been evaluated from the TG and DTG curves recorded at low heating
rates.
In celebration of the 60th birthday of Dr. Andrew K. Galwey 相似文献
The chemical synthesis of 3′-deoxyadenyly-(2′-5′)-3′-deoxyadenylyl-(2′-5′)-3′-deoxyadenosine ( 30 ; trimeric cordycepin) is described by three different routes using various protecting groups and applying the phosphotriester approach. The intermediates have been isolated and characterized by elemental analyses and spectroscopic means. High yields of 30 have been obtained on deprotection making this biologically very active compound available in preparative scale. 相似文献
In order to allow for the relative increase of self-interaction in few-electron systems, a reduction factor is introduced into the statistical free-electron exchange potential. This net-exchange potential has been used in the calculation of elastic electron scattering by rare-gas atoms in the low-energy region from 0 to 10 eV. Whereas former attempts to treat these phenomena as simple potential scattering have failed, in this work at least a crude qualitative agreement with experimental data has been achieved in most cases. 相似文献