Eine neue Methode zur Bestimmung geringer Konzentrationen von Nitroglykol und Nitroglycerin in der Luft

Zusammenfassung Auf geringe Konzentrationen von Nitroglykol und Nitroglycerin zu untersuchende Luft wird durch Äthanol/Wasser-Gemisch (11) geleitet, wobei die Salpetersäureester quantitativ aufgefangen werden. Nach Zugabe von Tetramethylammoniumbromid wird elektrolytisch bei einem Potential von –1300 mV gegen SCE, das mittels eines Potentiostaten konstant gehalten wird, reduziert. Die Reduktion führt unter den gewählten Bedingungen zu NO₂-, das in dem Elektrolyten nach Diazotierung von Sulfanilsäure und Kupplung mit -Naphthylamin photometrisch bestimmt wird. Die Methode hat bei guter Reproduzierbarkeit eine Empfindlichkeit von etwa 0,1 g/ml und eignet sich für Bestimmungen im Bereich der arbeitshygienischen Grenzkonzentrationen in Luft (MAK-Werte).

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Summary Low concentrations of ethylene glycol dinitrate and glycerol trinitrate to be determined in air are trapped in ethanol/water mixture (1:1). After addition of tetramethylammonium bromide, electrolytic reduction is performed at a constant potential of-1,300 mV vs. S.C.E. controlled by a potentiostat. The reduction quantitatively yields NO₂-which is determined photometrically with sulphanilic acid and alpha-naphthylamine within the electrolyte. The method has a sensitivity of about 0.1 g/ml and good reproducibility. The method proposed for the toxicological analysis in industrial hygiene is capable of measuring the maximum allowable concentration of ethylene glycol dinitrate and glycerol trinitrate in air.

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Der Verf. spricht Herrn Direktor Prof. Dr. G. A. Hunold, dem Leiter des Laboratoriums für chemische Toxikologie des Max von Pettenkofer-Institutes, den besten Dank für die Anregung und Förderung der vorliegenden Arbeit aus. Ferner dankt der Verf. Herrn Chemotechniker H. Wenske für die Ausführung der experimentellen Untersuchungen.     

Carbohydrate-protein interactions at interfaces: comparison of the binding of Ricinus communis lectin to two series of synthetic glycolipids using surface plasmon resonance studies

Two C-lactosyl lipids and the related C-galactosyl lipids have been synthesised and their binding to RCA120 plant lectin was compared with a second series of thiolactosylethoxyalkanes. The interactions were measured quantitatively in real time by surface plasmon resonance (BIAcore) at a range of concentrations and temperatures from 5 to 30 degrees C. The C-galactosyl lipid (1,3-dimethyl-5-[beta-D-galactopyranosyl]-5-(4-octadecyloxybenzyl)pyrimidine-2,4,6-trione) bound much more weakly with a K(A) = 8.86 x 10(5) than the corresponding C-lactosyl lipid (1,3-dimethyl-5-[beta-D-galactopyranosyl-(1 --> 4)-beta-D-glucopyranosyl]-5-(4-octadecyloxybenzyl)pyrimidine-2,4,6-trione) (K(A) = 2.31 x 10(7)). The influence of the linker region of the two different series of lactosyl lipids was clearly demonstrated by the differences in the binding to RCA120 lectin. The changes in kinetic values and in the enthalpic and entropic contribution to the free energy of binding reflected the importance of the linker and the hydrocarbon anchor holding the synthetic glycolipids in the neomembrane.     

Relationship between hydration energy of zeolites and cation distribution in their crystals

A method is proposed for calculating the heat of immersion of zeolites in water from data on the composition and density of the zeolite framework. The phenomenon of localization of some of the zeolite cations in the unhydrated crystallographic positions is explained. For ferrisilicates with the ZSM-5 structure, the fraction of iron atoms in the framework has been estimated from data on the energy of hydration.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 29, No. 2, pp. 174–179, March–April, 1993.     

Physicochemical aspects of the development of new functional materials based on heterosubstituted titanates of rare-earth elements with the Perovskite structure

In the example of titanates of rare-earth elements with the perovskite structure, relationships have been established for the influence of heterovalent substitution in the cation sublattices, through which the electrophysical properties within a single structural type can be controlled over a broad range, from microwave dielectrics to cationic conductors and semiconductors. V. I. Vernadskii Institute of General and Inorganic Chemistry, National Academy of Sciences of Ukraine, 32/34 Akademika Palladina Prospekt, Kiev-142 252680, Ukraine. Translated from Teoretischeskaya i éksperimental'naya Khimiya, Vol. 34, No. 6, pp. 331–346, November–December, 1998.     

Photosensitization of electronic transitions by dye molecules in systems consisting of a semiconductor and adsorbed molecules of p-benzoquinone

Electrophysical methods and ESR measurements have been used to investigate the changes, photosensitized by molecules of rhodamine B (RB), in the charge states of electron traps created by molecules of p-benzoquinone (pBQ) in the Ge/GeO₂ system. The results obtained in studying the quenching of fluorescence of RB molecules indicate that the photodestruction of electron traps is due to transfer of electronic excitation energy traps is due to transfer of electronic oxidation energy from the RB molecules to charged complexes formed upon adsorption of the pBQ. In order to select optimal conditions for recharging of such complexes, a study has been made of the relationship between the relative change in ESR signal and the concentration of adsorbed RB molecules.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 25, No. 5, pp. 545–550, September–October, 1989.     

Kinetics of p-cumylphenol alkylation by isobutylene in the presence of p-toluenesulfonic acid

Kinetics of p-cumylphenol alkylation by isobutylene in the presence of 0.1–2 wt.% p-toluenesulfonic acid has been studied and a reaction scheme is suggested. The rate constants have been determined.

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- 0,1–2 % . -. .

     

Diels-Alder versus heterodiene reaction: The effect of acid catalysis.

The difference between thermal, AlCl₃- and CF₃ COOH-catalyzed reaction of (E)-4-benzal-1-phenyl-5-pyrazolone and 2,3-dimethylbutadiene is discussed in terms of Diels-Alder $\text{versus}$ heterodiene reactivity.     

A new method for the direct calculation of resonance parameters with application to the quasibound states of the H2X1Σ g + system

A new method for the direct calculation of resonance parameters is presented. It is based upon searching for poles of the scattering matrix at complex energies. This search is expedited by the use of analytic derivatives of the scattering matrix with respect to the total energy. This procedure is applied initially to a single channel problem, but is generalizable to more complicated systems. Using the most accurate available potential energy data, we calculate resonance parameters for all of the physically important quasibound states of the ground electronic state of the hydrogen molecule. Corrections to the Born-Oppenheimer potential are included and assessed. The new method has no difficulty locating resonances with widths greater than about 1×10^–7 cm^–1. It is easier to find narrow resonances by monitoring the dependence of the imaginary part of the reactance matrix on the real part of a complex energy than to monitor the dependence of the eigenphase sum on energy at real energies.     

Surface reaction dynamics and the harmonic oscillator

One of the fundamental steps in chemical reaction dynamics involves breaking reactant bonds. This is facilitated by placement of energy into the vibrational degrees of freedom associated with the bond. Here we present a model for vibrational excitation in molecule-surface collisions in which the equilibrium geometry of the (diatomic) molecule varies with distance from the surface. The special feature of this model is that the potential energy surfaces for bound nuclear motion are constructed from quadratic potentials, thus enabling analytic solutions. Comparisons are made between exact results obtained from a purely classical trajectory model and various hybrid models in which the internal vibrational modes are treated quantum mechanically in the harmonic limit.