Epaminierungen. II. Herstellung von Aziridinen aus Olefinen und N-Halogenaminen

Epaminations. II. Synthesis of Aziridines from Olefins and N-Haloamines Chloramine, dichloramine as well as the N-chloro- and N-bromo-derivatives of primary aliphatic amines react with olefins to give aziridines. Yields up to 75% are obtained by the reaction of N.N-dibromamines with styrene-type olefins. The reaction is shown to proceed stereo-unspecifically by a chain-mechanism with the radical R N· Br as the chain carrier.     

Die zweite Geo‐Geum‐Brücke in Südkorea – Schrägkabelbrücke und Vorlandbrücke für Straßenverkehr mit Verbundfachwerkträger

The 2nd Geo Geum Grand Bridge in Korea – cable‐stayed bridge and approach bridge with composite truss girder for roadway traffic. The 2nd Geo Geum Grand Bridge forms part of the fixed connection from the mainland to the Island of Geo Geum in South Korea (Fig. 1). This high level crossing is composed of a 912 m long approach viaduct and a 1116 m long stay cable bridge with a main span of 480 m. The approach viaduct is a continuous girder with regular spans of 120 m. The superstructure of both bridges is a composite truss girder bridge, which carries a 2 lane highway on top and a pedestrian and bicycle way on the lower deck. The main design considerations were function as a high‐way, innovation in design and visual harmony with its surround‐ings. The stay cables are arranged in a single plane at the centre of the bridge, their semi‐fan arrangement with bundled configur‐ation gives a very special and unique appearance.     

Synthesis of Synthetic Lubricants by Trimerization of 1‐Decene and 1‐Dodecene with Homogeneous Chromium Catalysts

The Cr‐catalyzed trimerization of 1‐decene and 1‐dodecene is a highly selective method to synthesize C₃₀ and C₃₆ olefins. After hydrogenation, these products display very attractive viscosity indices (VI's). Due to the high trimer selectivity of the reaction no additional work‐up is needed to separate C₂₀, C₂₄ or C₄₀₊ oligomers from the product prior to a potential use of these products in synthetic lubricants for automotive applications.     

Fast Burning Rocket Propellants Based on Silicone Binders – New Aspects of an Old System

Fast burning rocket propellants based on ammonium perchlorate (AP) and polydimethylsiloxane (PDMS) binders have been formulated and basically characterized in aluminized and non aluminized versions. The thermodynamic performance of PDMS bound propellants is limited by the evaporation point of silicon dioxide (crystobalite at 2863 K), which is formed during the combustion. The maximum specific impulses calculated with an expansion ratio of 70 : 1 are I_SP = 2340 N s/kg (238 s) for AP/PDMS and I_SP = 2430 N s/kg (247 s) for AP/Al/PDMS formulations. With a tri‐modal AP‐fraction of 200 μm, 30 μm and 2 μm it was possible to achieve processable propellants with 83% and 84% solid loading. They give burning rates close to 60 mm/s at 10 MPa and pressure exponents between 0.5 and 0.6 in the range of 7–25 MPa. The thermodynamic specific impulse of these systems was calculated to I_SP=2319 N s/kg (236 s) for AP/PDMS and I_SP=2403 N s/kg (245 s) for AP/Al/PDMS formulations at 70 : 1 expansion ratio. Measurements of the glass transition point by DMA and TMA detected a time dependent partial crystallization of the used PDMS close to T_G in the temperature range from −44 °C to −60 °C. Basic tests reveal high thermal and chemical stability with flash points over 300 °C and zero detonation sensitivity at 50 mm diameter. The property profile, so far determined, tends to fulfil the demands for applications as propellants with high burning rates and operating pressures together with a high thermal stability and a low vulnerability.     

Einfache Darstellung von 4-Oxo-tetrahydropyrimidinen

Convenient Synthesis of 4-Oxo-tetrahydropyrimidines Enamino-nitriles as 6 or 11 yield 4-oxo-pyrimidines ( 2 ; 2a ; 10 ; 12a – c ) on treatment with cyclohexanone in basic media. Analogous compounds are obtained using acetone, butyraldehyde, benzaldehyde or substituted benzaldehydes.     

Elektrocyclische Synthese von aromatischen Aldehyden aus kettenförmigen Polymethinfarbstoffen

Electrocyclic Synthesis of Aromatic Aldehydes from Chain-shaped Polymethine Dyes Chain-shaped heptamethines form benzaldehyde by an electrocyclic reaction whereas nonamethines give cinnamic aldehyde. The Eyring parameters and the yields of the reaction are determined in dependence on the concentration of hydrogen ions.