Bicyclo[2.2.1]-2,5-heptadiene complexes of transition metal carbonyls have been treated with organometallic phosphines, to give the disubstituted compounds [(R3M′)3P]2M(CO)4 [R = CH3; M′ = Ge, Sn; M = Cr, Mo, W] by exchange of ligands. The chemical and spectroscopic properties of the new compounds are reported. 相似文献
Summary In this paper an approach is outlined to the two-dimensional analogon of the Gaussian quadrature problem. The main results are necessary and sufficient conditions for the existence of cubature formulae which are exact for all polynomials of degree m and which have a minimal number of 1/2k(k+1) knots,k=[m/2]+1. Ifm is odd, similar results are due to I.P. Mysovskikh ([5, 6]) which will be derived in a new way as a special case of the general characterization given here. Furthermore, it will be shown how this characterization can be used to construct minimal formulae of even degree. 相似文献
Integral cross sections for pure rotational and vibrational-rotational excitation of H2(X1Σ+g) by Li+(1S) impact are computed by close-coupling methods at 0.2, 0.6, and 1.2 eV in the c.m. system using vibrational functions that are numerical solutions of the one-dimensional radial Schrödinger equation for harmonic, Morse, and adiabatically corrected Kolos-Wolniewicz (KW) potential functions. Comparison of results employing KW and Morse functions shows excellent agreement for all transitions studied. Findings using harmonic oscillator functions, however, differ noticeably from KW and Morse values for vibrational (0 → 1) and very large rotational (Δj = 10) transitions, but are satisfactory for lower order (0 → 2, 4, 6, 8) rotational transitions. 相似文献
Two digestion-free methods for trace analysis of boron nitride based on graphite furnace atomic absorption spectrometry (GFAAS) and electrothermal vaporization inductively coupled plasma spectrometry optical emission (ETV-ICP-OES) using direct solid sampling have been developed and applied to the determination of Al, Ca, Cr, Cu, Fe, Mg, Mn, Si, Ti and Zr in four boron nitride materials in concentration intervals of 1–23, 54–735, 0.05–21, 0.005–1.3, 1.6–112, 4.5–20, 0.03–1.8, 6–46, 38–170 and 0.4–2.3 μg g− 1, respectively. At optimized experimental conditions, with both methods, effective in-situ analyte/matrix separation was achieved and calibration could be performed using calibration curves measured with aqueous standard solutions. In solid sampling GFAAS, before sampling, the platform was covered with graphite powder and, for determination of Si, also the Pd/Mg(NO3)2 modifier was used. In the determination of all analyte elements by solid sampling ETV-ICP-OES, Freon R12 was added to argon carrier gas. For solid sampling GFAAS and ETV-ICP-OES, the achievable limits of detection were within 5 (Cu)–130 (Si) ng g− 1 and 8 (Cu)–200 (Si) ng g− 1, respectively. The results obtained by these two methods for four boron nitride materials of different purity grades are compared each with the other and with those obtained in analysis of digests by ICP-OES. The performance of the two solid sampling methods is compared and discussed. 相似文献
Unusual assignments have been observed for the 1H-NMR of alkoxy groups in syndiotactic methyl methacrylate-methacrylic acid (MMA-MAA) copolymers and methyl methacrylate-diphenylmethyl methacrylate (MMA-DPMMA) copolymers. Thereby, the alkoxy groups OCH3 and OCH show a degenerate pentad assignment, in as much as the two monomer units nearest to the central monomer unit exert no differentiating influence on chemical shift, in contrast to the two next-to-nearest monomer units. By the use of copolymers possessing a tendency toward alternation with respect to compositional statistics, it is possible to distinguish between a degenerate pentad and a normal triad assignment. The reason for the degenerate pentad assignment is seen in specific conformations of the pentads, leading to the elimination of the differentiating influence on chemical shift for the two monomer units nearest to the central unit. 相似文献
This paper is focused on the use of branched poly(ethyleneimine) (PEI) as reducing as well as stabilizing agent for the formation of gold nanoparticles in different media. The process of nanoparticle formation was investigated, in the absence of any other reducing agents, in microemulsion template phase in comparison to the nucleation process in aqueous polymer solution.
On the one hand, it was shown that the polyelectrolyte can be used for the controlled single-step synthesis and stabilization of gold nanoparticles via a nucleation reaction and particles with an average diameter of 7.1 nm can be produced.
On the other hand, it was demonstrated that the polymer can also act as reducing and stabilizing agent in much more complex systems, i.e. in water-in-oil (w/o) microemulsion droplets. The reverse microemulsion droplets of the quaternary system sodium dodecylsulfate (SDS)/toluene–pentanol (1:1)/water were successfully used for the synthesis of gold nanoparticles. The polymer, incorporated in the droplets, exhibits reducing properties, adsorbs on the surface of the nanoparticles and prevents their aggregation. Consequently, nanoparticles of 8.6 nm can be redispersed after solvent evaporation without a change of their size.
Nevertheless, the polymer acts already as a “template” during the formation of the nanoparticles in water and in microemulsion, so that an additional template effect of the microemulsion is not observed.
The particle formation for both methods is checked by means of UV–vis spectroscopy and the particle size and size distribution are investigated via dynamic light scattering and transmission electron microscopy (TEM). 相似文献
Skeleton Rearrangement of an α-β-Unsaturated γ,δ-Epoxyketone during Birch Reduction: Structure Elucidation by Means of 13C-INADEQUATE-NMR Spectroscopy When the γ-epoxide 2 of β-ionone is treated under standard Birch-reduction conditions, unexpectedly a 70% combined yield of regioisomeric octalones 4 and 5 is isolated. These products unquestionably result form cleavage of the central epoxide C?C bond. The structure of compounds 4 and 5 could be determined by means of 13C-INADEQUATE-NMR spectroscopy. 相似文献
Zusammenfassung Die durch direkte Silylierung von Carbonamidgruppen mit Halogensilanen nicht zugänglichen Verbindungen der Gruppierung R-CONHSiR3 konnten durch Umsetzung von Säureamiden oder Säurechloriden mit Hexamethyldisilazan gewonnen werden. So wurden Derivate mit R=CH3, C2H5, C6H5, CONHSiR3, OCH3, OC2H5, OCH(CH3)2; R=CH3 (vgl. Tab. 1) dargestellt und in ihren physikalischen und chemischen Eigenschaften näher studiert.Herrn Prof. Dr.A. Zinke zum 70. Geburtstag gewidmet.15. Mitt.:U. Wannagat undH. Kuckertz, Angew. Chem.74, 117 (1962).Auszug aus der DissertationJ. Pump, Techn. Hochsch. Aachen 1962. 相似文献
The OH--catalysed hydrolysis of p-nitroacetanilide and p-nitroacetanilide-1-d3 has been studied between pH11·5 and 13·5 at 30°. The value of the secundary isotope effect is changed with respect to the OH--concentration. The inverse istope effects at high OH--concentrations (Hkkorr/Dkkorr = 0·87 ±0·05) and the opposite effects in the lower OH?-concentration ranges (Hkkorr/Dkkorr = 1·08 ± 0·04)are discussed on the basis of change in the rate limiting step. 相似文献