An expedient preparation of Stryker's reagent

A convenient and efficient preparation of Stryker's reagent, [Ph₃PCuH]₆, under homogeneous conditions using silanes as the reducing agent is detailed. The reaction time can be reduced to 1-2 h, and high yields of Stryker's reagent can be routinely achieved. The same method has been extended to the synthesis of [Ph₃PCuD]₆ using Ph₂SiD₂.     

Sensing the chirality of Dawson lanthanide polyoxometalates [alpha1-LnP2W17O61]7- by multinuclear NMR spectroscopy

Lanthanide complexes of the chiral Dawson phosphotungstate [alpha(1)-P(2)W(17)O(61)](10-) were used to study the formation of diastereomers with optically pure organic ligands. The present work started with the full assignment of the (183)W NMR spectra of [alpha(1)-Yb(H(2)O)(4)P(2)W(17)O(61)](7-) at different temperatures and concentrations, which allowed the structure of the dimerized form in aqueous solution to be established. Different enantiopure amino acids and phosphonic acids were screened as ligands. Both types allowed chiral differentiation by multinuclear NMR spectroscopy under fast-exchange conditions. Functional groups with a good affinity for the oxo framework of the polyoxometalate were identified, and maps of the interactions between L-serine and N-phosphonomethyl-L-proline with [alpha(1)-Yb(H(2)O)(4)P(2)W(17)O(61)](7-) were established. This demonstrates the power of (183)W NMR spectroscopy to elucidate the molecular recognition of inorganic molecules by organic compounds. N-Phosphonomethyl-L-proline appears to be a convenient ligand to promote separation of the diastereomers and ultimately resolution of the enantiomers of [alpha(1)-Yb(H(2)O)(4)P(2)W(17)O(61)](7-).     

The Alkylation of 6-Bromo-1,4-dihydro-4-oxo-3-cinnolinecarboxylic Acid

Alkylation of the title compound gave 3a, b + c and 2a, b + c in ca. equivalent yields. Intermediate 4a was isolated and its facile decarboxylation to 2a was studied.     

Kinetics of gas-phase addition reactions of methyl radicals. I. Addition to ethylene,acetylene, and benzene

The reactions have been studied by a mass-balance method involving the photolysis of small amounts of biacetyl in the presence of a large excess of isobutane containing a small proportion of the unsaturated substrate. The following Arrhenius parameters have been derived:

Certification of the contents of some heavy metals (Cd, Co, Cu, Mn, Hg, Ni, Pb and Zn) in three types of sewage sludge

Summary The element contents of Cd, Co, Cu, Mn, Hg, Ni, Pb and Zn of three different types of sewage sludge were certified. The preparation, the homogeneity and the stability are reported. The certified contents as well as values for Cr and Se and for the aqua regia soluble contents of Cd, Cr, Co, Cu, Mn, Ni, Pb and Zn are given.

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Zertifizierung von Schwermetallspuren (Cd, Co, Cu, Mn, Hg, Ni, Pb und Zn) in drei Klärschlammproben

Zusammenfassung In drei verschiedenen Klärschlammproben wurden die Elementgehalte an Cd, Co, Cu, Mn, Hg, Ni, Pb und Zn zertifiziert. Es wird berichtet über die Herstellung, Homogenität und Stabilität. Die zertifizierten Gehalte sowie der Gehalt von Cr, Se und der Gehalt an königswasserlöslichem Cd, Cr, Co, Cu, Mn, Ni, Pb und Zn werden angegeben.

     

Linear Convergence Rates for Variants of the Alternating Direction Method of Multipliers in Smooth Cases

In the present paper, we propose a novel convergence analysis of the alternating direction method of multipliers, based on its equivalence with the overrelaxed primal–dual hybrid gradient algorithm. We consider the smooth case, where the objective function can be decomposed into one differentiable with Lipschitz continuous gradient part and one strongly convex part. Under these hypotheses, a convergence proof with an optimal parameter choice is given for the primal–dual method, which leads to convergence results for the alternating direction method of multipliers. An accelerated variant of the latter, based on a parameter relaxation, is also proposed, which is shown to converge linearly with same asymptotic rate as the primal–dual algorithm.     

Development of the parametric tolerance modeling and optimization schemes and cost-effective solutions

Most of previous research on tolerance optimization seeks the optimal tolerance allocation with process parameters such as fixed process mean and variance. This research, however, differs from the previous studies in two ways. First, an integrated optimization scheme is proposed to determine both the optimal settings of those process parameters and the optimal tolerance simultaneously which is called a parametric tolerance optimization problem in this paper. Second, most tolerance optimization models require rigorous optimization processes using numerical methods, since closed-form solutions are rarely found. This paper shows how the Lambert W function, which is often used in physics, can be applied efficiently to this parametric tolerance optimization problem. By using the Lambert W function, one can express the optimal solutions to the parametric tolerance optimization problem in a closed-form without resorting to numerical methods. For verification purposes, numerical examples for three cases are conducted and sensitivity analyses are performed.