Ein Metaarsenat(V) Anion neuartiger Konstitution in AgAsO3

Metaarsenate(V) Anion of Novel Constitution in AgAsO₃ AgAsO₃ was prepared, for the first time, through solid state reaction of Ag₂O and As₂O₃, or As, respectively, while applying an elevated oxygen pressure (T = 500 °C, p(O₂) = 2 kbar, 1—2 days). The crystal structure (Pca2₁; a = 1948.8(3), b = 660.0(1), c = 1266.1(3) pm; Z = 24; 4741 independent reflexions; R₁ = 0.044) contains a novel polyanion, equation/tex2gif-stack-2.gif[(AsO_6/2)(AsO_2/1O_2/2)₂], with arsenic in an octahedral and tetrahedral coordination, at the same time. It thus features structural units similar to those in binary As₂O₅.     

Interpolation regions for convex cubic curve segments

Given a family of planar, convex, cubic curve segments with fixed end points and tangents, subregions of the plane are characterized in which additional points can be interpolated by at least one member of the family. The region for a second additional point is a remarkably thin double crescent.     

Theoretical investigation of the isomerization of trans-HCOH to H2CO: an example of a water-catalyzed reaction

A concerted hydrogen atom transfer mechanism has been elucidated for the isomerization of trans-HCOH to H(2)CO using a variety of ab initio and density functional theory methods. This work places specific emphasis on the role water molecules can play as a catalyst for this reaction and the mechanism by which this is achieved. This is of particular importance in the context of molecular ices in the interstellar medium because the presence of water in this reaction reduces the activation energy by at least 80%, which is accompanied by a significant enhancement of the reaction rate, at ≤300 K.     

Electrosynthesis of substituted 1H-indoles from o-nitrostyrenes

A novel procedure has been devised for the synthesis of derivatives of 1H-indole that is based on the direct, room-temperature electrochemical reduction of substituted o-nitrostyrenes at carbon cathodes in N,N-dimethylformamide containing tetramethylammonium tetrafluoroborate as supporting electrolyte and in the presence of a 10-fold molar excess of a proton donor (phenol or methyl 3-oxobutanoate).