Uranyl ion-selective optode based on neutral ionophores

A pulsed molecular beam Fourier transform microwave spectrometer especially designed for the quantitative analysis of polar pollutants in air is presented. This very fast method has a sensitivity in the ppm range and can be applied to a wide variety of substances. Details of the apparatus and the results of some performance tests are given.     

N,N,N′,N′-Tetrabutyl-3,6-dioxaoctan-dithioamid,Ionophor mit Selektivität für Cd2+

N,N,N′,N′-Tetrabutyl-3,6-dioxaoctane-dithioamide, an Ionophore with Selectivity for Cd²⁺ The dioxa-dithioamide 3 behaves as a highly selective ionophore for Cd²⁺ in solvent polymeric membranes. It induces cation-permselectivity in these membranes with a transference number of 1 for Cd(NO₃)₂- and of 2 for CdCl₂-solutions. In the presence of a proton carrier, 3 may be used to selectively pump Cd²⁺ through membranes by coupling with a pH gradient.     

A three-component coupling process based on vicarious nucleophilic substitution (VNS(AR))-alkylation reactions: an approach to indoprofen and derivatives.

The intermediate anion derived from the vicarious nucleophilic substitution (VNS) of hydrogen reacts with a series of alkyl halides to generate the corresponding alpha-alkylated conventional VNS product in a one-pot process. This one-pot VNS-alkylation reaction offers a convenient route to a range alpha-substituted nitrobenzyl phosphine oxides, sulfones, and esters via a three-component coupling reaction. Reactions of alpha-chloroethyl phenyl sulfone (14) and ethyl 2-chloropropionate (16) with nitrobenzene followed by subsequent addition of an alkylating agent give a series of sulfones and esters bearing an alpha-aryl quaternary center. The VNS-alkylation protocol has been applied to the synthesis of derivatives of Indoprofen from nitrobenzene using readily available inexpensive starting materials. Indoprofen itself was prepared using the conventional VNS reaction in four steps and 24% overall yield from nitrobenzene.     

Structure analysis of intercalated layer silicates: combination of molecular simulations and experiment

Na(+)-montmorillonite type Wyoming, cloisite Na(+) from Southern Clay Products, Inc., was intercalated (i) with octadecylammonium cations and subsequently intercalated with octadecylamine molecules, (ii) with dodecylamine molecules, and (iii) with octylamine molecules to determine the applicability of these intercalates for nanocomposite materials on the base of polymer/clay. The structures were determined on the basis of a combination of results from X-ray diffraction and molecular simulations. The calculated values of basal spacings are in good agreement with experimental basal spacings when experimental samples were prepared. The interlayer space of intercalated montmorillonite shows a monolayer or bilayer arrangement of alkyl chains in dependence on the concentration of the intercalation solution. The values of the total sublimation energy, interaction energy, and exfoliation energy were calculated for all investigated samples. Low values of exfoliation energies lead to better exfoliation of intercalated silicate layers and this material appears suitable for use as a precursor for polymer/clay nanocomposites. The values of exfoliation energy for the investigated samples show that montmorillonite intercalated with dodecylamine or octadecylamine molecules is suitable for exfoliation of silicate layers.     

Role of elemental fluorine in nuclear field

The preparation of fluorine gas by Henri Moissan by electrolysis of molten fluorides can be considered as one of the most important discoveries during the last centuries. Indeed, in addition to its use in many industrial fields (microelectronic, surface cleaning, pharmacology, medicine, …), fluorine gas is strongly involved in nuclear field for the preparation of UF₆. The latter allows the natural uranium enrichment via the gaseous diffusion process. Due to the increase of the energy demand in industrialised and emergent countries, the production of UF₆ and consequently of F₂ should increase drastically during the next decades. The aim of this paper is to summarise the evolution of the process to produce fluorine from its discovery to the present process. Few aspects on the researches done for a better understanding of the fluorine evolution reaction are presented. The use of fluorine in the nuclear field is also discussed.     

Isolation of a new member of the ecdysteroid glycoside family: 2-deoxy-20-hydroxyecdysone 22-O-beta-D-glucopyranoside

A new ecdysteroid glycoside, 2-deoxy-20-hydroxyecdysone 22-O-beta-D-glucopyranoside, is isolated from the herb Silene italica ssp. nemoralis (Waldst. and Kit.) Nyman. The compound is purified with multistep chromatography, such as classical column chromatography on alumina and droplet countercurrent distribution. Also, it is expanded using twice low-pressure reversed-phase liquid column chromatography. Chromatography in four steps results in the purified 2-deoxy-20-hydroxyecdysone 22-O-beta-D-glucopyranoside. Two other ecdysteroids have also been separated, including the formerly identified integristerone A and 24(28)-dehydromakisterone A.     

Covalent attachment of a nickel nitrilotriacetic acid group to a germanium attenuated total reflectance element

The surface of a germanium internal reflectance element (IRE) was modified to bind 6X-histidine (his)-tagged biomolecules. The step-by-step surface modification was monitored via single-pass attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FT-IR). Initially an adlayer of 7-octenyltrimethoxysilane (7-OTMS) was formed on the Ge crystal through the surface hydroxyl groups, which were produced via ozonolysis of the Ge surface. The vinyl moiety of 7-OTMS was oxidized to a carboxylic acid, which was activated by 1,1'-carbonydiimidazole (CDI) to produce a labile imidazole. The labile imidazole that resulted from the CDI coupling was then displaced by the primary amine of nitrilotriacetic acid (NTA). Nickel sulfate was added to the system, and it coordinated with the three carbonyl groups and the nitrogen on NTA, thus leaving the ability of Ni to coordinate with two adjacent histidine residues. Binding of his-tagged biotin to nickel nitrilotriacetic acid (Ni-NTA) was observed by ATR-FT-IR spectroscopy. The surface modification method presented in this paper had minimal nonspecific binding, the Ni-NTA surface was reusable if stored properly, and complete removal of the organic surface was achievable.     

Nitrogen bridgehead compounds part 21. Preparation of new quaternary 2,3a,6a-triazaphenalenium salts

The first representatives of a new ring system, the 2,3a,6a-triazaphenalenium quaternary salts are prepared by the cycloaddition of tetrahydro-4H-pyrido[1,2-a] pyrimidin-4-ones containing an α-chloroenamine moiety with azomethines.     

Synthese und Struktur von [(Ph3PAu)3NPPh3][PF6]2, einem Gold(I)‐phosphoraniminato‐Komplex

Synthesis and Crystal Structure of [(Ph₃PAu)₃NPPh₃][PF₆]₂, a Gold(I) Phosphoraneiminato Complex The photolytic reaction of Ph₃PAuN₃ with Cr(CO)₆ in THF yields the phosphoraneiminato complex [(Ph₃PAu)₃NPPh₃]²⁺ in low yield as well as the cluster cation [(Ph₃PAu)₈]²⁺ as the main product. The phosphoraneiminato complex crystallizes from CH₂Cl₂ with [PF₆]^? ions as [(Ph₃PAu)₃NPPh₃][PF₆]₂·CH₂Cl₂ in the triclinic space group with a = 1200.8(1), b = 1495.6(2), 2053.5(5), α = 86.97(2)°, β = 82.79(1)°, γ = 81.87(2)°, and Z = 2. The phosphoraneiminato ligand bridges through its N atom three Au atoms, which itself are connected to each other by weak aurophilic interactions.     

On the Structure of the Spectra for a Class of Combustion Waves

The stability of a premixed laminar flame supported by a general combustion reaction system is considered using the Evans function method. The spectrum of the linearised second-order differential operator is investigated in detail. The special structure of the differential equations due to an Arrhenius temperature dependence is exploited. It is shown that, for certain combustion systems, the limit of the Jacobian of the reaction terms as the travelling wave coordinate approaches the front and rear of the flame is a lower triangular matrix. For this type of system a simple geometrical method is shown for the study of the essential spectrum of the linearised operator, and for determining the domain of the Evans function. The results are applied to some representative combustion reactions.