Systematische untersuchungen über das verhalten von organozinn-verbindungen gegenüber flüssigem schwefeldioxid VI. Zum mechanismus der SO2-einschiebung in die zinn—kohlenstoff-bindung

SO₂-insertion reactions of tetraorganostannanes in liquid sulphur dioxide proceed through an open transition state. Arguments favouring an S_E2 mechanism are presented on the basis of investigations on tetraalkyl-, tetraaryl-, and tetraalkenyl-stannanes, mixed substituted and perfluorinated tetraorganotin compounds as well as organotin halides.     

Pfaffsche Formen auf komplexen Räumen

Ohne Zusammenfassung     

Precise asymptotics in some strong limit theorems for multidimensionally indexed random variables

Consider Z₊^d (d2)—the positive d-dimensional lattice points with partial ordering , let {X_k,kZ₊^d} be i.i.d. random variables with mean 0, and set S_n=∑_knX_k, nZ₊^d. We establish precise asymptotics for ∑_n|n|^r/p−2P(|S_n||n|^1/p), and for

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, (0δ1) as 0, and for

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as .     

Trace-level determination of pesticides in food using difficult matrix introduction-gas chromatography-time-of-flight mass spectrometry

A procedure for the fully automated analysis of food samples by means of difficult matrix introduction-gas chromatography-time-of-flight mass spectrometry (DMI-GC-ToF MS) is discussed. After extraction, samples require very little clean-up and are injected in a micro- or micro-vial which is held in a liner. Next, the liner is placed in the injector and the contents of the vial are thermally desorbed and led directly to the capillary GC column. After GC-ToF MS analysis, the data are processed automatically using a peak deconvolution algorithm. The practicability of the procedure was demonstrated by analysing spiked grape and pineapple samples down to the 1-10 ng/g concentration level.     

Integral representations for the alternating groups

We show that every complex representation of an alternating group can be realized over the ring of integers of a ``small' abelian number field.

     

Methylation with sodium naphthalenide for the analysis of substituent distribution of trimethylsilyl celluloses and their evaluation

The substitution pattern of trimethylsilyl celluloses silylated withhexamethyldisilazane and N,N-dibutylamino­trimethylsilane was determined bymethylation analysis. Methylation with sodium hydride/methyl iodide wasaccompanied by significant desilylation because sodium hydride is alwayscontaminated with sodium hydroxide. Sodium naphthalenide prepared in tetrahydrofuran under anhydrous reaction conditions alloweda reduction of the extent of desilylation to less than 10 percent. In allcases preferred silylation of the 6-position was found. Celluloses silylatedwith hexamethyldisilazane and N,N-dibutylaminotrimethylsilane had almostidentical substituent distributions. Lower reaction temperature resulted inhigher regioselectivity.