Synthesen von Heterocyclen, 108. Mitt.: Über Reaktionen mit Salicylsäurechlorid

Zusammenfassung Salicylsäurechlorid (1) reagiert mit Campherimin ·HCl bzw. Campheranil oder mit Aldazinen zu Derivaten des 1,3-Benzoxazin-4-ons.

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Salicoyl chloride reacts with camphorimine hydrochloride and camphoranile or with aldazines to give derivatives of 1.3-benzoxazin-4-ones.

     

Wasserstoffumlagerungen bei der elektronenstoßinduzierten Fragmentierung von Aminoäthern

Due to neighbouring group effects the behaviour under electron impact of amino ethers of the type RO(CH₂)_nNR₁R₂ is distinctly different from that of both simple ethers and amines. In addition to α-cleavages two further primary fragmentations can often be observed, one leading to [M–aldehyde]^+. or [M–ketone]^+. ions, the other (with n≥3) giving [M–R]⁺ ions. Both processes involve hydrogen rearrangements which were investigated by means of deuterium labelling. Their importance is strongly dependent upon the nature of the substituents R, R₁, R₂ and upon the length (n) of the carbon chain between the heteroatoms. This dependence can easily be explained by the fragmentation mechanisms put forward.     

Synthesen von Heterocyclen, 150. Mitt.: Über Reaktionen mit cyclischen Oxalylverbindungen, 4. Mitt.

Zusammenfassung Von den Pyrrol-2,3-dion-3-hydrazonen5–8 läßt sich lediglich7 in das Pyrrolo[2,3–b]indol-3-hydrazon (10) umlagern. Die analogen Heterocyclen9, 11 und12 sind durch direkte Einwirkung der entsprechenden Hydrazine auf die Pyrrolo[2,3–b]indole3 bzw.4 synthetisierbar.

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Syntheses of Heterocycles, CL: Reactions of Cyclic Oxalyl compounds, IV

Of the pyrrol-2,3-dione-3-hydrazones5–8 only7 can be rearranged to give the pyrrolo[2,3–b]indole-3-hydrazone10. The heterocyclic compounds9, 11, and12 are synthesized by the action of the corresponding hydrazines upon the pyrrolo[2,3–b]indoles3 and4, respectively.

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Herrn Dr. techn. Dr. rer. nat. h. c. Dr. phil. h. c.W. G. Stoll, Forschungsdirektor der Ciba-Geigy-AG, Basel, zum 60. Geburtstag gewidmet.     

Ultra-rapid separation of an angiotensin mixture in nanochannels using shear-driven chromatography

The present paper reports on the separation of a mixture of fluorescein isothiocyanate-labeled angiotensin I and II peptides in a shear-driven nanochannel with a C18-coating and using an eluent consisting of 5% acetonitrile in 0.02 M aqueous phosphate buffer at pH 6.5. The flat-rectangular nanochannel in fused silica consisted of an etched structure in combination with a flat moving wall. The very fast separation kinetics that can be achieved in a nanochannel allowed to separate the angiotensin peptides in less then 0.2 s in a distance of only 1.8 mm. Plate heights as small as 0.4 microm were calculated after substraction of the injection effect.     

Effect of ionic liquid on dielectric, mechanical and dynamic mechanical properties of multi-walled carbon nanotubes/polychloroprene rubber composites

This paper focuses on the influence of ionic liquid on carbon nanotube based elastomeric composites. Multi-walled carbon nanotubes (MWCNTs) are modified using an ionic liquid at room temperature, 1-butyl 3-methyl imidazolium bis (trifluoromethylsulphonyl) imide (BMI) and modified MWCNTs exhibit physical (cation–π/π–π) interaction with BMI. The polychloroprene rubber (CR) composites are prepared using unmodified and BMI modified MWCNTs. The presence of BMI not only increases the alternating current (AC) electrical conductivity and polarisability of the composites but also improves the state of dispersion of the tubes as observed from dielectric spectroscopy and transmission electron microscopy respectively. In addition to the hydrodynamic reinforcement, the formation of improved filler–filler networks is reflected in the dynamic storage modulus (E′) for modified MWCNTs/CR composites in amplitude sweep measurement upon increasing the proportion of BMI. Hardness and mechanical properties are also studied for the composites as a function of BMI.     

A Study on Transreactions of PET/PEN Reactive Blending in a Twin‐Screw Extruder Using an Axial Dispersion Model

Transreactions of PET and PEN melt‐mixed in a twin‐screw extruder are investigated. The extruder is modeled and characterized in the frame of a tubular system of closed type. The kinetic modeling is based on a modified second‐order reversible reaction equation, which allows the dispersion equation to be solved analytically. The analysis shows a good agreement between the model and experiment. The axial dispersion model is employed to predict the extent of transesterification reactions (X) and degree of randomness (RD). ¹H NMR measurements are performed to estimate X and RD. Theoretical and experimental data are in good agreement. The model can thus be exploited to describe the effects of processing parameters, mixing time, mixing temperature, and blend composition on X and RD.

     

Vibrational spectroscopic studies and DFT calculations on tribromoacetate and tribromoacetic acid in aqueous solution

Aqueous solutions of sodium tribromoacetate (NaCBr3CO2) and its corresponding acid (CBr3COOH) have been studied using Raman and infrared spectroscopy. The spectra of the species in solution were assigned according to symmetry Cs. Characteristic bands of CBr3CO2-(aq) and the tribromoacetic acid, CBr3COOH(aq), are discussed. For the hydrated anion, the CO2 group, the symmetric CO2 stretching mode at 1332 cm(-1) and the asymmetric stretching mode at 1651 cm(-1) are characteristic while the CO mode at 1730 cm(-1) is characteristic for the spectra of the acid. The stretching mode, νC-C at 912cm(-1) for CBr3CO2-(aq) is 10 cm(-1) lower in the anion compared with that of the acid. These characteristic modes are compared to those in acetate, CH3CO2-(aq). Coupling of the modes are fairly extensive and therefore DFT calculations have been carried out in order to compare the measured spectra with the calculated ones. The geometrical parameters such as bond length and bond angles of the tribromoacetate, and tribromoacetic acid have been obtained and may be compared with the ones published for other acetates and their conjugated acids. CBr3COOH(aq) is a moderately strong acid and the pKa value derived from quantitative Raman measurements is equal to -0.23 at 23°C. The deuterated acid CBr3COOD in heavy water has been measured as well and the assignments were given.