Investigation of the reaction order for nucleophilic substitution of dialkyl methylphosphonates by alkoxides

The rate of nucleophilic substitution at the phosphorus centre of dialkyl methylphosphonates by methoxide and ethoxide has been studied to investigate the possible involvement of hexacoordinated phosphorus species in this reaction. For alkoxide concentrations less than ca. 1.5 M the rate increases with the square of alkoxide concentration. However, consideration of the activity of the alkoxides, represented by an appropriate acidity function, reveals that only one equivalent of alkoxide is involved in the rate-determining step. Thus, there is no requirement to invoke the intermediacy of a hexacoordinated species in the reaction pathway. © John Wiley & Sons, Inc.     

Deformations of incompressible bodies with free boundaries

Communicated by C. Dafermos     

Poincaré series and holomorphic averaging

Summary We provide an alternate proof of McMullen's theorem on contractive properties of the Poincaré series operator in the special case of the universal covering. This case includes in particular Kra's Theta Conjecture.Oblatum 16-X-1991 & 14-IV-1992First author supported in part by a grant from the National Science Foundation     

Multilayers as defect barriers

A multilayer structure consisting of undoped GaAs and AlAs layers was incorporated into a buffer layer on GaAs substrates. This reduces the spreading of impurities from the substrate (e.g. tellurium) into layers deposited on top of the multilayer system as observed by SIMS and C/V profiling. Incorporation coefficients for tellurium in GaAs, AlAs and multilayers were calculated.     

Validation of a solid-phase extraction high-performance liquid chromatographic assay for doxazosin.

The determination of doxazosin by high-performance liquid chromatography with fluorescence detection is described. Propanolol was used as the internal standard. Plasma samples were treated with methanol to precipitate the proteins. Doxazosin was isolated with C18 reversed-phase extraction columns. The determination limit is 1 ng/ml of plasma, while the extraction columns can be reused frequently. The method is applied to clinical trial samples.     

Complete assignment of the 1H and 13C NMR Spectra of 11,12-Dimethoxy[1]benzothieno[3,2-a]-4,7-phenanthroline and its 8-Chloro Analogue: Concerted Use of Two-Dimensional NMR Techniques

The ¹H and ¹³C nmr spectra of 11,12-dimethoxy[1]benzothieno[3,2-a]-4,7-phenanthroline and its 8-chloro precursor were totally assigned using a combination of two-dimensional nmr techniques. After correlation of the majority of the proton signals by a COSY spectrum and one-bond heteronuclear correlation, the full assignment of the ¹H and ¹³C nmr spectra of the novel heterocyclic compounds required the application of long-range CH coupling information particularly for quaternary carbon resonance assignments and the orientations of individual spin systems relative to one another. Key long-range heteronuclear couplings in both compounds served to confirm the one-bond heteronuclear correlations. Unequivocal interpretation of the spectral data leads to the complete assignments of the resonances.