Specific determination of 20 primary aromatic amines in aqueous food simulants by liquid chromatography-electrospray ionization-tandem mass spectrometry

A multi-analyte method without any pre-treatment steps using reversed-phase liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) was developed and applied for the determination of 20 primary aromatic amines (PAA) associated with polyurethane (PUR) products or azo-colours. The method was validated in-house for water and 3% acetic acid food simulants using spiked migrates from plastic laminates. Detection limits ranged from 0.27 to 3 microg amine/L food simulants, and RSD values of within-laboratory reproducibility at the 2 microg PAA/L level ranged from 3.9 to 19%. PAA migration from plastic laminates and black nylon cooking utensils were determined with the method, and high levels of 4,4'-methylenedianiline and aniline were found in migrates from about half of the tested cooking utensils. The method fulfils present legislative demands in the EU for screening and verification of PAA migration from food contact materials.     

A boxmodel development to study the relationships between the photo-oxidants and the particles formation in the troposphere

The model BAGS (Boxmodel for Aerosol and Gasphase Simulations) has been developed. It is composed of two major modules: the first one describes the system of the chemical reactions in the gaseous phase, the second one calculates the aerosol chemical composition and the dimensional distribution of the particles. The boxmodel has been developed with the introduction of new chemical and physical processes, not previously included, in particular the formation of Secondary Organic Aerosol. The other implemented processes are a module for the dynamic of the particle population, nucleation, coagulation and dry deposition. The last phase of the work has been a check of the BAGS capabilities by a series of tests, that have permitted to compare it with other models (MAPS and MADM). The tests in particular have concerned the aerosol water content prediction, the photochemistry, the condensation of the inorganic compounds and the formation of Secondary Organic Aerosol.     

Zur Kenntnis der NaCl-Strukturfamilie Die Kristallstruktur von NaMnO2

To the Knowledge of the NaCl Family of Structure: The Crystal Structure of NaMnO₂ Ochre coloured single crystals of NaMnO₂ show a monoclinic [a = 5.662 Å, b = 2.860 Å, c = 5.799 Å, β = 113.1°] variant [C–C2/m; Na in 2(d), Mn in 2(a), O in 4(i), R = 11.2% (MoK_α)] of the α-NaFeO₂-type of structure. The Jahn-Teller-distortion within the {MnO₆}-Group ist remarkable with Mn ? O = 1.93 (4×), 2.40 (2 ×) Å. NaMnO₂ posesses temperature indepent paramagnetism: +_Mol =+3450 · 10^?6 cgs. The Madelung Part of Lattice Energy is calculated and discussed.     

Coexistence of multiple conformations in cysteamine monolayers on Au(111)

The structural organization, catalytic function, and electronic properties of cysteamine monolayers on Au(111) have been addressed comprehensively by voltammetry, in situ scanning tunneling microscopy (STM) in anaerobic environment, and a priori molecular dynamics (MD) simulation and STM image simulation. Two sets of voltammetric signals are observed. One peak at -(0.65-0.70) V (SCE) is caused by reductive desorption of cysteamine. The other signal, at -(0.25-0.40) V consists of a peak doublet. The pH dependence of the latter suggests that the origin is catalytic dihydrogen evolution. The doublet feature is indicative of two distinct cysteamine configurations. Cysteamine monolayer formation from initial nucleation to a highly ordered phase has been successfully observed in real time using oxygen-free in situ STM. Random cellular patterns, disordered adlayer formation accompanied by high step edge mobility, and ultimately a highly ordered (square root 3 x 4) R30 degrees lattice are observed sequentially. Pits are formed due to enclosure of the mobile edges during the adsorption process. In the highly ordered cysteamine layer, each unit has two spots with apparent 0.6 A height difference in STM images. The coverage 5.7 +/- 0.1 x 10(-10) mol cm(-2) determined by voltammetry supports that the spots represent two individual cysteamine molecules. A priori MD and density functional simulations hold other clues to the image interpretation and indicate that the NH(3)(+) groups dominate the tunneling contrast. A wide range of interface structures, showing variations in the sulfur binding site and orientation, gauche and trans conformers, and especially hydrogen-bonding interactions, are examined, from which it is concluded that the adsorbate structure is controlled by interactions with the solvent rather than with the substrate.     

Synthese,Struktur und einige Reaktionen [N-(N′,N′,N″,N″-tetramethyl)-guanidinyl]-substituierter Phosphorylverbindungen

Synthesis, Structure, and some Reactions of N-(N′,N′,N″,N″-tetramethyl)guanidinyl-substituted Phosphoryl Compounds The tetramethylguanidinyl-substituted phosphoryl compounds 1 – 10 were prepared in the reaction of the appropriate chlorophosphoryl compounds with either N′,N′,N″,N″-tetramethylguanidine (HTMG) or N-trimethylsilyl-(N′,N′,N″,N″-tetramethyl)guanidine (TMSTMG). With methyl iodide 1 reacted with N-alkylation to give the ammonium salt 11. 1 reacted with BF₃ · Et₂O at both imino nitrogen atoms with formation of the bis-BF₃-adduct 12 . The X-ray structure determination of phenylphosphonic acid-bis(N′,N′,N″,N″-tetramethylguanidinide) 3 shows shortened PN-bonds and widened PNC-angles, consistent with the partial double bond character of the PN-bond.     

Synthesis of enantiomerically enriched allenes by (-)-sparteine-mediated lithiation of alkynyl carbamates

[reaction: see text]. The alpha-deprotonation of alkynyl carbamates 3 with the chiral base (-)-sparteine (4)/n-butyllithium, transmetalation with ClTi(O(i)()Pr)3, and subsequent substitution with an aldehyde results in the formation of enantioenriched 4-hydroxyallenyl carbamates 11. Stereoselection is determined by dynamic resolution of the lithium/(-)-sparteine complexes by selective crystallization.     

Notiz über Li2PdO2

Note on Li₂PdO₂ For the first time we prepared ruby-red single crystals of Li₂PdO₂ by reaction with the wall 3 Na₂O + Li₂O₂ + ?Tb₄O₇”?(+ Pd) = 3 Na₂TbO₃ + Li₂PdO₂ + ?TbO₂”?, Pd-tube, 1100°C, 7 d. Single crystal data confirm the Li₂CuO₂-type of structure [a = 375.34(5), b = 298.18(4), c = 931.58(10) pm; spacegroup Immm; d_x = 4.85 g · cm^?3; 144 I₀(hkl); R = 3.54%, Rw = 3.19%; MoKα ; four-circle diffractometer Philips PW 1100] and reveal clearly different parameters compared with those deduced by powder data. The Madelung Part of Lattice Energy, MAPLE, corresponds now to the sum of the MAPLE values of the binary oxides.     

Watching photoinduced chemistry and molecular energy flow in solution in real time

Energized molecules are the essential actors in chemical transformations in solution. As the rearrangement of bonds requires a movement of nuclei, vibrational energy is often the driving force for a reaction. Vibrational energy can be redistributed within the "hot" molecule, or relaxation can occur when molecules interact. Both processes govern the rates, pathways, and quantum yields of chemical transformations in solution. Unfortunately, energy transfer and the breaking, formation, and rearrangement of bonds take place on ultrafast timescales. This Review highlights experimental approaches for the direct, ultrafast measurement of photoinduced femtochemistry and energy flow in solution. In the first part of this Review, we summarize recent experiments on intra- and intermolecular energy transfer. The second part discusses photoinduced decomposition of large organic peroxides, which are used as initiators in free radical polymerization. The mechanisms and timescales of their decarboxylation determine the initial steps of polymerization and the microstructure of the polymer product.     

Über Fluoride des zweiwertigen Eisens: Ba2[Fe3F10]

On the Knowledge of Ba₂[Fe₃F₁₀] For the first time colourless single crystals of Ba₂Fe₃F₁₀ have been prepared by reduction of a mixture of 3 BaF₂/7 FeF₃ in a Fe-tube (reaction with the wall 750°C, 60 d). Ba₂Fe₃F₁₀ crystallizes in the monoclinic spcgr. P2₁/c with a = 788.3(1), b = 623.0(1), c = 1868.0(3) pm, β = 111.79(1)º, Z = 4. (Fourcircle diffractometer PW 1100, Fa. Philips, MoKα, 2383 of 2383 I₀(hkl), R = 8.1%, R_w = 4.1%, parameters see in the text). The Madelung Part of Lattice Energy, MAPLE, is calculated and discussed.     

XRD-Studies of SiC/Si layers on carbon substrates

Structural investigations of thin films of SiC, SiC with free silicon and various titanium suicides (TiSi₂, TiSi and Ti₅Si₃) are described. The crystal phases have been identified using X-ray diffractometry. The growth of reaction products from surface reactions between silicon and deposited titanium can be observed.Dedicated to Professor Dr. rer.nat. Dr. h.c. Hubertus Nickel on the occasion of his 65th birthday