A New Samarium Diiodide Induced Reaction: Intramolecular Attack of Ketyl Radical Anions on Aryl Substituents with Formation of 1,4-Cyclohexadiene Derivatives

Beware of samarium diiodide and aryl ketones! If the ketyl radical anion which is formed by electron transfer finds a properly placed aryl group, a highly diastereoselective cyclization may occur. After the transfer of a second electron and protonation bi- and polycyclic products with a common 1,4-cyclohexadiene moiety may be isolated [Eq. (a)]. X=CHCO₂R, NCH₂Ph; HMPA=(Me₂N)₃PO.     

Characterization of Mixing Efficiency in Polymerization Reactors Using Competitive-Parallel Reactions

Summary: In this article particular attention is paid to processes of mixing fluids with different viscosities relevant for polymerization where the reaction is fast and mixing is the limiting factor. Apart from this, mixing fluids with different viscosities is still one of the challenging tasks in industrial chemistry. Therefore, the characterization of mixing elements is another important topic. Two different multiple chemical reactions, based on the principle of competitive-parallel reactions, were used and compared to investigate (micro)mixing efficiency in polymerization reactors. The well-known Villermaux-Dushman reaction and the third Bourne reaction were applied. The observed product distribution represents the quantity of segregation of the fluid which gives in turn information about the dependency on certain parameters like type and speed of stirrer, dosing period, feed position, and the viscosity of the fluid. The results from semibatch and continuous stirred tank reactors and two different stirrers, Rushton and INTERMIG^® impeller, are discussed.