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71.
New samarium carbene complexes have been synthesized and characterized by X-ray diffraction analysis; the carbenic nature was assessed by reactivity studies.  相似文献   
72.
A one-pot synthesis of substituted imidazoles is described. The cornerstone of this methodology involves the thiazolium-catalyzed addition of an aldehyde to an acyl imine to generate the corresponding alpha-ketoamide in situ followed by ring closure to the imidazole in a one-pot sequence. The extension of this methodology to the one-pot synthesis of substituted oxazoles and thiazoles is also described. [reaction: see text]  相似文献   
73.
In designing an experimentin which non-linear regression analysis is used to evaluate the physicochemical parameters that chracterize the behavior of the system being studied, it would be useful to be able to predict how the number of data points affects th reliabilities of the values obtained. The relation between these depends on hos the points are distributed as well as on the nature of the equation to which thd data are fitted. Weighted non-linear regression analysis has been applied to six common equations involving a total of fourteen parameters, using a number of n of points that was varied from 4 to  相似文献   
74.
The hydrogen evolution reaction (HER) was investigated on a lanthanum-phosphate-bonded nickel (LPBN) powder electrode in 30 wt.% NaOH at 70°C using ac impedance and steady-state polarization techniques. Circuits containing one or two constant-phase elements (CPEs) in parallel with a resistance and corresponding to fractal and porous electrode models were tested in order to interpret the ac impedance data. The experimental impedance spectra were well described by the porous electrode model and the circuit containing two CPEs. The results obtained from the ac impedance and steady-state measurements allowed the mechanism and kinetics of the HER to be evaluated. Comparison of these parameters with those obtained on the polycrystalline nickel electrode in 1 M alkaline solution at 25°C indicates that an increase in activity is principally due to an increase in the real surface area.  相似文献   
75.
A new liquid chromatography-mass spectrometry technique is described that utilizes a particle beam interface to transport and deposit desolvated analyte molecules onto a target surface that is bombarded by a primary beam of massive multiply charged glycerol cluster ions to generate secondary ions for mass analysis. The massive cluster ion beam is generated by electrohydrodynamic emission from a solution of 1. 5-M ammonium acetate in glycerol. In the present instrumental configuration the massive cluster ion gun is placed above the target probe and the particle beam interface is connected through a side port of the mass spectrometer. The massive cluster ion beam and particle beam are intercepted by a target surface substituted for a conventional ion volume. The target surface is positioned such that it is ~ 45 ° to the primary cluster ion beam, the particle beam, and the mass analyzer axis. This geometric orientation represents a compromise among the performances of these three elements. The feasibility of this liquid chromatography-particle beam on-line with massive cluster impact is demonstrated by flow injections of acetylcholine chloride and gramicidin S. Spectra generated from this preliminary study indicate promise for routine liquid chromatography-mass spectrometry of polar compounds by using a robust inlet and an effective generation of secondary ions without an added matrix.  相似文献   
76.
Kinetics of thermal decomposition in vacuum of Co3O4 powder as well as single crystals has been investigated. Discrepancies with the results of previous authors have been discussed. Decomposition of Co3O4 proceeds through formation of a compact layer of CoO and hence diffusion is the rate-limiting factor. The experimental curves α(t) be described for 0.05 < α < 0.85 using a modified Ginstling-Brounshtein equation: 1 ? 2α/3 ? (1 ? α)2/3 = ktn where the activation energy varies with the degree of decomposition.  相似文献   
77.
 The molecular ion 1 of N-(n-propoxy)benzaldimine I rearranges by an 1,5-H-shift to the δ-distonic ion 2 which subsequently cyclizes to the α-distonic ion 3. Homolytic cleavage of the N–O bond in 3 results in the δ-distonic ion 4 which expels CH2O leading to the β-distonic ion 5. Ion 5 is also formed from the molecular ions of tetrahydrooxazines II and III and from M+• of phenylazetidine IVa. In a subsequent step, ion 5 cyclizes to the N-protonated 3,4-dihydroisoquinolinium ion 6. The syntheses of IIIV and their derivatives are described.  相似文献   
78.
Replacement of C-4 with a hetero substituent (NR,O,S) in the 1-vinyl-3,4-dihydronaphthalene system has provided a new type of diene for participation in the McCormack cycloaddition reaction with P(III) halides. The tricyclic phospholene oxides so obtained are the first to bear an additional heteroatom in the ring system. 1,2-Dihydro-7-methoxy-1-(p-toluenesulfonyl)-4-vinylquinoline is a stable solid that reacts with methylphosphonous dichloride to give, after hydrolysis of the cycloadduct, the 1,2,4,5-tetrahydro-1H-phospholo-[2,3-c]quinoline ring system. The dihydroquinoline moiety was aromatized by detosylation with potassium t-butoxide. The tendency of 4-vinyl-2H-benzopyran to dimerize was a serious complication in its use, and the cycloaddition with methylphosphonous dichloride proceeded only in low yield. The product, a 2,3,3a,4-tetra-hydrobenzo[3,2-d]pyran derivative, was a stable, easily purified and characterized substance. 4-Vinyl-2H-benzo[b]thiopyran was more stable than the pyran, but the phospholo derivative from reaction with methylphosphonous dichloride was more difficult to purify. All products were characterized by 13C-nmr spectroscopy.  相似文献   
79.
The synthesis of poly(hydridocarbyne), one of a class of carbon-based random network polymers and a structural isomer of polyacetlyene, is reported. The network backbone of this polymer is primarily composed of tetrahedrally hybridized carbon atoms, each bearing one hydride substituent and linked via three carbon-carbon single bonds into a three-dimensional random network of fused rings. This atomic-level carbon network backbone confers unusual properties on the polymer, including facile thermal decomposition to form diamond or diamond-like carbon high-quality films at atmospheric pressure, by direct deposition or by chemical vapor deposition (CVD), without the use of hydrogen or any other reagent.  相似文献   
80.
DFT calculations have been performed with the B3LYP and MPW1K functional on the hydrogen atom abstraction reactions of ethenoxyl with ethenol and of phenoxyl with both phenol and alpha-naphthol. Comparison with the results of G3 calculations shows that B3LYP seriously underestimates the barrier heights for the reaction of ethenoxyl with ethenol by both proton-coupled electron transfer (PCET) and hydrogen atom transfer (HAT) mechanisms. The MPW1K functional also underestimates the barrier heights, but by much less than B3LYP. Similarly, comparison with the results of experiments on the reaction of phenoxyl radical with alpha-naphthol indicates that the barrier height for the preferred PCET mechanism is calculated more accurately by MPW1K than by B3LYP. These findings indicate that the MPW1K functional is much better suited than B3LYP for calculations on hydrogen abstraction reactions by both HAT and PCET mechanisms.  相似文献   
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