Evaluation of the sulfur(IV) catalyzed autoxidation of cobalt(II) in an azide containing medium as a means for the determination of sulfite in precipitation

Summary The sulfur(IV) catalyzed oxidation of cobalt(II) by dissolved oxygen in azide containing medium has been investigated with respect to its analytical potentialities. The strong absorptivity at 365 nm of the cobalt(III)/azide-complex formed makes possible the establishment of a simple and fast spectrophotometric method for sulfite determinations in aqueous solution. With manganese(II) as an activator and 5 cm cuvettes for absorption measurements the working range is between 5×10^–7 and 5×10^–5 mol/l sulfite. The new method has been successfully applied to the investigation of rain water samples. Of the potential interferences only those originating from iron(III) and formaldehyde are of practical relevance. The first one can be avoided by proper blank correction, the second by a slight modification of the procedure.

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Untersuchung der durch Schwefel(IV) katalysierten Autoxidation von Cobalt(II) in azidhaltiger Lösung im Hinblick auf ihre Anwendung zur Bestimmung von Sulfit in NiederschlÄgen

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Dedicated to Prof. Dr. W. Fresenius on the occasion of his 75th birthday     

Synthesis of new beta-substituted meso-tetraphenylporphyrins via 1,3-dipolar cycloaddition reactions. 1

The azomethine ylide generated from the reaction of (beta-formyl-meso-tetraphenylporphyrinato)nickel(II) with N-methylglycine reacts with a range of dipolarophiles, yielding new beta-substituted-meso-tetraphenylporphyrins. The regio- and stereochemistry of the new compounds was established using one- and two-dimensional NMR techniques.     

Isolation and structural elucidation of 5-formyl-2,3-dihydroisocoumarin from Centaurium erythraea aerial parts

An isocoumarin was isolated from the aerial parts of Centauriwn erythraea Rafn. (Gentianaceae). Its structure was established by spectroscopic means as 5-formyl-2,3-dihydroisocoumarin.     

Effects of substrate polarity and chain length on conformational and thermal properties of phosphonic acid self-assembled bilayers

Conformational and thermal behavior of self-assembled structures of three phosphonic acids, OPA (octadecylphosphonic acid), TPA (tetradecylphosphonic acid), and OcPA (octylphosphonic acid), with different alkyl chain lengths are investigated and compared. The orientation of self-assembled bilayers depends on whether the substrate is nonpolar (graphite) or polar (mica). For nonpolar substrates, bilayers lay parallel to the surface, and for polar substrates, bilayers lay perpendicular to the surface. Thermal behaviors of these structures on mica and graphite are also investigated, showing that, depending on the temperature they are submitted to, molecules stack, unstack, or agglomerate on mica and form larger domains on graphite.