Experimentelle Untersuchungen zur Ionisierung und Umladung von Alkanolen durch 6-25 keV Wasserstoffionen

Experimental Investigations of Ionisation and Charge-transfer of Alcohols by 6-25 keV Hydrogen Ions Ionisation and charge-transfer cross sections were measured for the interaction of H⁺, H and H ions (in the energy range 6-25 keV) with alcohols (methanol-octanol). The cross sections depend significantly on the target molecular structure like molecular length, ionisation potential, polarizability and atomic bonds in the target molecule.     

Anwendung der GRYZINSKY-Theorie zur Berechnung der Ionisierungs- und Umladungwirkungsquerschnitte für die Wechselwirkung von Wasserstoffionen und Alkanolmolekülen

An Application of GRYZINSKY -theory to Calculations of Ionisation and Charge-transfer Cross Sections for the Interaction of Hydrogen Ions with Alcohol Molecules Ionisation and charge-transfer cross sections were calculated for the interaction of H⁺, H and H ions (energy range 5-25 keV) with alcohols (methanol-butanol). A modified GRYZINSKY approximation is used for the calculation of the cross sections. The calculated values have been compared with experimental determined cross sections. The agreement between experimental results and theoretical results is satisfactory.     

Synthesis of periphery-functionalized dendritic molecules using polylithiated dendrimers as starting material

A general method for the functionalization of Si-Cl terminated carbosilane dendritic molecules via organolithium or organomagnesium reagents is described. Quantitative exchange of the bromine atoms of 4-bromophenyl-functionalized dendrimers affords polylithiated species that are valuable starting materials for further functionalization, e.g., into pyridyl alcohols. The latter were successfully applied as catalyst precursors in a ruthenium-mediated ring-closure metathesis reaction.     

Chemie der Seltenerdmetalle, 19. Mitt.: Dissoziation des Ce(III)-succinats im sauren Gebiet

Zusammenfassung Die Dissoziation von Ce₂ Suc ₃·3 H₂O^** in Perchlorsäure-Lösungen wurde verfolgt und die Dissoziationskonstanten der Succinationen: (CeSuc)⁺ und (CeSuc ₂)^– unter Benützung einer Löslichkeitsmethode in 1m-NH₄ClO₄-Lösung bei 25°C bestimmt. Die Löslichkeitsprodukte von Ce₂ Suc ₃: [Ce³⁺]²[Suc ^2–]³, [CeSuc ⁺]²[Suc ^2–], [CeSuc ⁺][CeSuc ₂ ^–] wurden bestimmt.

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The dissociation of Ce₂ Suc ₃·3H₂O in perchloric acid solutions was investigated. The dissociation constants of the succinate ions (CeSuc)⁺ and (CeSuc ₂)^– were determined inM-NH₄ClO₄ at 25° using a solubility method and the solubility products of Ce₂ Suc ₃, i. e. [Ce³⁺]²[Suc ^2–]³, [CeSuc ⁺]²[Suc ^2–], [CeSuc ⁺][CeSuc ₂ ^–] measured.

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18. Mitt.:R. Pastorek, Lanthantartrate im neutralen und alkal. Bereich. Mh. Chem.99, 676 (1968).     

Phototropie von niedergeschlagenem AgBr-Aerosol

Zusammenfassung Mit einer Drahtexplosion von Silberdraht in einer Brom/Argon-Atmosphäre wurde AgBr-Aerosol hergestellt und auf einer Quarzglasplatte niedergeschlagen. Bei Bestrahlung der so gebildeten Schicht im UV-Spektralbereich von 300–400 nm ergab sich eine Schwärzung, die nach Unterbrechung der Einstrahlung wieder zurückging (Phototropie), wenn die Schicht mit Bromdampf in Berührung stand. Mit Laserlichtbeleuchtung wurde an mehreren Schichten der zeitliche Verlauf der Remission gemessen und dabei Bestrahlungsstärke, Bromdampfdichte und Belegungsdichte der Schicht variiert. Zunehmender Bromgehalt hat aufhellende Wirkung. Die gemessenen Schwärzungs- und Regenerationszeiten sind etwa 10mal kleiner als die von handelsüblichen phototropen Gläsern. Zur phänomenologischen Deutung der Ergebnisse wurde ein einfaches reaktionskinetisches Modell aufgestellt, das 4 Konstanten enthält, die aus dem Experiment bestimmt wurden. Dabei wurde die Konzentrationsabhängigkeit der die Remission kennzeichnendenKubelka-Munk-Funktion herangezogen.Summary A silver wire exploding in an atmosphere of bromine and argon provides the generation of a silver bromide aerosol which is precipitated on a quartz glass plate. As the layer formed in this way is submitted to ultraviolet radiation ranging from 300 to 400 nm, a blackening occurs which, after interruption of the emitted radiation, decreases again (phototropy) when the layer is in contact with the bromine vapor. A laser beam is used to measure the development with time of the reflectance of various layers. For this the irradiante, bromine vapor concentration, and surface density of the layer are being varied. The increase in the content of bromine causes the blackening to attenuate. Both the measured blackening and regeneration durations are approximately ten times shorter than those of commercially available phototropec glasses. In order to explain these phenomena as well as the relating results, a simple kinetic model was established including four constants which were determined from the experiment. For this theKubelka-Munk function was used characterizing the reflectance as a function of concentration.

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Mit 10 Abbildungen     

Nuclear structure effects in light π- mesoatoms

Performing the angle transformation from pion-nucleon to pion-nucleus CMS frame the first order pion-nucleus optical potential receives also a contribution due to nucleonic Fermi motion. The corresponding term is always repulsive and reflects the nuclear spin-orbital interaction playing an important role particularly for nuclei with half-filled valence shells. We demonstrate the effects due to this term yielding a contribution to the level shifts and widths of pionic atoms. Such ideas allow one to explain theA-dependence of 2p-level energy shifts for most of the s-d shell-mesoatoms.Dedicated by the co-authors to the memory of M. Gmitro.Two authors (A. C. and R. M.) are grateful to Prof. H. J. Leisi, Prof. M. P. Locher and Dr. P. F. A. Goudsmit for stimulating discussions and hospitality extended to them during their stay at Paul Scherrer Institute.     

The catalytic system [(Cp2TiCl)2]:LiAlH4 in aromatic solvents,Part II. Formation of η3-allyltitanocene derivatives in the presence of dienes — their structure and e.s.r. spectra

Summary The addition of dienes to the system [(Cp₂TiCl)₂] LiAlH₄toluene changes the system so that the complex [Cp₂TiAlH₄] is quantitatively formed instead of a titanocene hydride — aluminium hydride cluster. The complex [Cp₂TiAlH₄] is further converted into ³-allyltitanocene derivatives ([Cp₂TiA]) if the diene structure is suitable for formation of stable [Cp₂TiA] compounds and if the equilibrium [Cp₂TiAlH₄]+diene[Cp₂TiA]+A1H₃ is shifted towards the formation of [Cp₂TiA] by the excess of diene. All the compounds [Cp₂TiA] exhibit high-resolution e.s.r. spectra at g=1.993, showing interaction of the unpaired electron with the cyclopentadienyl and ³-allyl protons. The e.s.r. spectra clearly reveal the presence of alkyl substituents atsyn-1,3-positions of ³-allyl ligand, and show a triplet of multiplets for (³-allyl)titanocene, doublets of multiplets for (1-alkyl-³-allyl)titanocenes and single multiplets for (1,3-dialkyl-³-allyl)-titanocenes. thermal isomerization of (1,3-dimethyl-³-allyl)-titanocene and (1-methyl-3-ethyl-³-allyl)titanocene, hitherto considered as the stable Cp₂TiA compounds, into (1-alkyl-³-allyl)titanocenes was confirmed by e.s.r. and electronic absorption spectroscopy as well as by chemical means.     

Regularity of weak solutions to rate‐independent systems in one‐dimension

We show that under some appropriate assumptions, every weak solution (e.g. energetic solution) to a given rate‐independent system is of class SBV, or has finite jumps, or is even piecewise C¹. Our assumption is essentially imposed on the energy functional, but not convexity is required.     

Spectral properties of coumarin derivatives in various environments

The structural and spectral properties of coumarin derivatives in complex environments were investigated within the time-dependent density functional theory (TD DFT). Absorption spectra calculations were obtained at TD PBE0/6-31+G(d,p) level of theory for coumarin47 in the gas-phase and in various polar and non-polar organic solvents. The geometries of coumarins 6, 30, 47 and 522 in the gas phase and in inclusion complexes with the β-cyclodextrin (βCD) were determined by PM3 and DFT (HCTH/6-31G) calculations. Encapsulation of coumarin in βCD and associated changes in electronic structure produced either a red or blue shift in the absorption spectra of coumarins. A proposed cavity model for βCD-coumarin complex in water solution allowed identification of various contributions to the overall shift in the absorption spectra of coumarin upon complex formation in a solvent environment      

Simultaneous determination of inorganic arsenic,antimony, selenium and tellurium by ICP-MS in environmental waters using SPE preconcentration on modified silica

This paper deals with a simplified multi-element profiling of inorganic arsenic, antimony, selenium and tellurium in the form of ⁷⁵As, ⁸²Se, ¹²¹Sb and ¹²⁵Te by ICP-MS for amounts less than 10?µg?L^?1. Internal standards such as ⁷²Ge and ²⁰⁹Bi were successfully used for the suppression of both influence of macro elements Na⁺, K⁺, Ca²⁺, Mg²⁺ or Al³⁺, and interference of limited concentrations of heavy metal ions. Modified silica sorbents Separon? SGX C18, C8, CN, NH₂, RPS and Phenyl were tested for the preconcentration of As, Sb, Se and Te (0.25–5?µg?L^?1) in the form of ion associates with cationic surfactants from 50–250?mL sample volume. 1-etoxycarbonyl-pentadecyltrimethylammonium bromide (Septonex®, 0.005?mol?L^?1) was suitable for this purpose in the presence of 4-(2-pyridylazo) resorcinol, 2-pyrrolidinecarbodithioate and 8-hydroxyquinoline-5-sulphonic acid. The quantitative retention occurred at pH 7?±?0.2 and the mixture of acetone with ethanol in ratio 1?:?1 in the presence of 0.1?mol?L^?1 HCl was used for the quantitative elution. Organic solvents and the excess of acid were removed by evaporation prior to the determination by ICP-MS. The determination of the above trace metalloids in various kinds of water with enrichment factor till 50 times on silica Separon? SGX C18 and the above reagents were compared with the standard addition method.