Chlorherstellung mit Sauerstoffverzehrkathoden. Energieeinsparung bei der Elektrolyse

Chlorine is one of the most important base chemicals and is required for the manufacture of about two‐thirds of all chemical products such as polymers, crop protection and pharmaceutical products, products for drinking water purification, and ultrapure silicon for photovoltaics and electronics applications. The industrial chlorine production through the chlor‐alkali electrolysis has since 1975 mainly been based on the advanced membrane process. Chlorine recycling by manufacturing processes based on hydrogen chloride has also become increasingly important. The still very high energy demand for the electrochemical chlorine synthesis can be significantly reduced by up to 30 % if the hydrogen evolving cathodes in the classical processes are replaced by oxygen depolarized cathodes (ODC) which are well known from fuel cells. Hydrogen chloride electrolysis with ODCs is already carried out in world‐scale plants. The more important chlor‐alkali process with ODCs will be realized for the first time in 2011 in a demonstration unit with a chlorine capacity of 20000 tons per year in Uerdingen, Germany.     

Computer plots of HOH normal modes depending on time

The combination of the antisymmetric and symmetric stretching vibrations of water is a decoupled OH vibration. It means the X₁₃ anharmonicity constant of HOH must be related with the X₃₃ anharmonicity constant of HOD. It is found that $\text{1}\text{2}$X₁₃(HOH)= X₃₃(DOH) = X(OH). Instead of the usual condition X_ik = 0 for i > k a new definition will be given for the anharmonicity constants: $\text{X}$_ik = $\text{X}$_ki. The X values of other molecules were compared with each other and it follows the general rule for a symmetric molecule m-M-m with m ? M: $\text{X}$₁₃ (mMm) = $\text{X}$₃₁ (mMm) = X (Mm).Computer plots of normal modes of the ν₁ + ν₃ combination depending on time show the rotation of the dipole moment derivatives vector. It is strongly different for H₂O and HOD and explains the different band intensities. We expect higher band intensities and X₁₃ values using IR light with rotating electric field vector.     

Lactam analogues of galiellalactone

A synthetic route to lactam analogues of the fungal STAT3 inhibitor galiellalactone is presented. The synthesis involves a one-pot tosylamide amide coupling/intramolecular Michael addition and an introduction of an α,β-unsaturation, regioselectively directed by the tosyl functionality. An iodolactonization of the octahydroindolizine 9 and a re-opening of the lactone were employed for introducing an iodo substituent, facilitating the preparation of 8-substituted analogues (e.g., 4) using a Suzuki cross-coupling.     

On the production of \pi^{+}_{} \pi^{+}_{} pairs in pp collisions at 0.8 GeV

Data accumulated recently for the exclusive measurement of the pp $ \rightarrow$ pp $ \pi^{+}_{}$ $ \pi^{-}_{}$ reaction at a beam energy of 0.793GeV using the COSY-TOF spectrometer have been analyzed with respect to possible events from the pp $ \rightarrow$ nn $ \pi^{+}_{}$ $ \pi^{+}_{}$ reaction channel. The latter is expected to be the only $ \pi$ $ \pi$ production channel, which contains no major contributions from resonance excitation close to threshold and hence should be a good testing ground for chiral dynamics in the $ \pi$ $ \pi$ production process. No single event has been found, which meets all conditions for being a candidate for the pp $ \rightarrow$ nn $ \pi^{+}_{}$ $ \pi^{+}_{}$ reaction. This gives an upper limit for the cross-section of 0.16μb (90% C.L.), which is more than an order of magnitude smaller than the cross-sections of the other two-pion production channels at the same incident energy.     

Free-knot spline approximation of stochastic processes

We study optimal approximation of stochastic processes by polynomial splines with free knots. The number of free knots is either a priori fixed or may depend on the particular trajectory. For the s-fold integrated Wiener process as well as for scalar diffusion processes we determine the asymptotic behavior of the average L_p-distance to the splines spaces, as the (expected) number of free knots tends to infinity.     

A Lennard-Jones-like perspective on first order transitions in biological helices

Helical structures with Lennard-Jones self-interactions are studied for optimal conformations. For this purpose, their self-energy is analyzed for extrema with respect to the geometric parameters of the helices. It is found that Lennard-Jones helices exhibit a first order phase transition from a state with large curvature of the helical backbone to one with a small curvature. I.e. from a dense helix to an extended helix. A transition from one helical structure to another is a phenomenon known to take place in self-assembling helices formed in multicomponent solutions with cholesterol.     

Sol–gel processing at increased temperatures: the formation of polyester nanocomposites

Polyester nanocomposites were prepared using sol–gel precursors, prehydrolyzed sols, or nanoparticles in polyester formulations. The different inorganic components were introduced in the early stages of the esterification reaction and a typical polymerization temperature program was applied leading to temperatures up to 240 °C at low pressures. The structural and physical properties of the final materials depend on the applied method for the introduction of the sol–gel materials. Silicon atoms were incorporated into the polyester chain if silicon tetraalkoxide was used as precursor. The silicon atoms represent branching points in the polymer structure. Prehydrolyzed sols that were prepared under acidic conditions were another source of silicon and formed larger inorganic aggregates in the polymer matrix. Nanoparticles prepared via the Stöber process were the third inorganic species in polyester formation. All three processing pathways produced different kinds of materials depending on the type of silica incorporated in the polyester networks but also with regard to the nanoscale structure of the materials. Both, composition and structure have a major influence on the final polyester nanocomposite properties. Model reactions between silicon tetraalkoxides and diols or diacids using the temperature program for the polyester formation showed that exchange reactions of the alkoxides and the alcohols or acids can occur and the obtained products can carry out side reactions in the polyester formation. The final materials show a homogeneous distribution of the silicon containing moieties in the polyester matrix. The viscosities and the branching degrees of the polymers changed dramatically compared to the pristine polymers by incorporation of the sol–gel precursors.     

Competitive Formation of Ylide and Carbene Intermediates from 1π,π*-Excited α,β-Unsaturated γ,δ-Epoxyketones

Laser flash photolyses (λ = 265mm) of the γ,λ-epoxyenones 1–3, 7 and 8 , the α,β-unsaturated γ,δ-epoxy ester 6 , and the epoxytriene 9 at ambient temperature produced short-lived transients with broad absorption maxima in the visible region, which are identified as carbonyl ylides. Comparison of the rather long-wavelength absorption maxima with the results of standard PPP SCF SCI calculations suggests that some degree of twisting is present in all the ylides studied. The lifetimes of the order of hundreds of ns of these intermediates and Stern-Volmer analysis of the trapping of the carbonyl ylide derived from 2 with CH₃COOH provide conclusive evidence that the carbene products are not formed via the carbonyl-ylide intermediate (Scheme 3).     

The He(Iα) Photoelectron Spectra of the Perfluoroderivatives of Trisannelated Benzenes and Tetrakisannelated Cyclooctatetraenes

The He(Iα) photoelectron (PE) spectra of tris(perfluorocyclobuta)benzene 4 (F)

1 3,3,4,4,7,7,8,8,11,11,12,12-Dodecafluorotetracyclo[8.2.0.0^2,5.0^6,9]dodeca-1,5,9-triene

, tris(perfluorocyclopenta)benzene 5 (F)

2 1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9-Octadecafluoro-2,3,4,5,6,7,8,9-octahydro-1H-trindene.

, tetrakis(perfluorocyclobuta)cyclooctatetraene 6 (F)

3 3,3,4,4,7,7,8,8,11,1l,l2,l2,l5,15,16,16-Hexadecafluoropentacyclo[12.2.0.0^2,5.0^6,9.0^10,13]hexadeca-1,5,9,13-tetraene.

, and of tetrakis(perfluorocyclopenta)cyclooctatetraene 7 (F)

4 1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12-Tetracosafluoro-1,2,3,4,5,6,7,8,9,10,11,12-dodeca-hydrotetracyclopenta[a,c,e,g]cyclooctene.

are reported. A tentative assignment of the PE spectra is derived by empirical correlation with those of relevant reference compounds. The results suggest that 6 (F) retains the D_4h-conformation in the gas phase, i.e. A conformation with a planar cyclooctatetraene ring, as observed in the crystal. All four compounds exhibit a sharp increase of their first ionization energies, relative to the corresponding parent hydrocarbons, due to the perfluoro effect.