Diels-Alder-Reaktionen von Vinylindolen mit Arin und 1,4-Benzochinonen: Neue potentielle DNA-Interkalatoren

Summary Diels-Alder reactions of 2- and 3-vinylindoles with aryne, 1,4-benzo- and 1,4-naphtho-quinone lead to new six-ring annellated carbazoles. Molecular modeling studies predict that the compounds with coplanar framework are able to intercalate with the B-DNA.

     

Electrocatalysis by foreign metal monolayers: Oxidation of formic acid on platinum

It was demonstrated that some foreign metal monolayers formed by underpotential deposition have pronounced catalytic effects on the oxidation of formic acid on platinum. The explanation of these effects was sought within the framewor of existing data on the formic acid oxidation and the underpotential deposition. It was found that the catalytic effect of foreign metal monolayers originates in the decrease of hydrogen adsorption thus preventing the formation of the main poisoning species COH. At the same time these experiments confirm the previously postulated mechanism of formation of the poisoning species involving adsorbed hydrogen.     

New evidence on the structure of potassium salts of 12-tungstophosphoric acid, KxH3-xPW12O40

Physicochemical properties and compositions of KxH(3-x)PW12O40 salts, where 2 < or = x < or = 3, have been investigated. It has been found that freshly prepared K2HPW12O40 salt (drying at 313 K) contains particles of heteropolyacid and particles of the neutral potassium salt, the sample being in 78.6% amorphous. On aging at room temperature, the heteropolyacid spreads to form a surface layer covering the neutral potassium salt particles K3PW12O40. Heat treatment of KxH(3-x)PW12O40 salts, where 2 < or = x < 3, from 313 K to higher temperatures induces the transformation of the heteropolyacid-covering K(3) core into a well-dispersed, amorphous surface layer. On further heating of the acidic potassium salts, the surface layer decomposes between 855 and 915 K with the formation of a PW8O26-type bronze as a new phase, the K3PW12O40 salt remaining unchanged. The latter starts to decompose at 1093 K, and in the case of all samples, the process is completed at about 1183 K. Rietveld structure refinement, XPS, and 31P NMR measurements of acidic potassium salts indicate that the core of these salts is always formed by the K3PW12O40 salt, which is covered by a heteropolyacid. Comparison of lattice parameters of the K3 salt and HPW leads to the conclusion that the layer is composed of partially or completely dehydrated heteropolyacid molecules. The coverage of the core by HPW in the K2 sample was estimated to be equal to one monolayer.     

The polymorphic transformations of cobalt molybdate

Polymorphic transformations of CoMoO₄ were studied by means of high temperature X-ray measurements within the temperature range 25–1200°C. On heating phase a obtained from low temperature modification b a new modification a′ was discovered. Phase a obtained by thermal decomposition of solvated α-CoMoO₄ shows different behaviour. At 700–930°C depending on the conditions of preparation it transforms irreversibly into still another modification a″. On cooling, a mixture of phases a + a″ is obtained, the presence of a″ being responsible for the explosionwise transition into b, observed around the room temperature.     

IR-spectroscopic studies of the interaction of propylene and acrolein with a CoMoO4 catalyst

IR spectra of propylene and acrolein adsorbed at different temperatures on CoMoO₄ supported on MgO were recorded. Four different surface species were found: a -complex, an oxygen bonded carbonyl complex, acrylic acid and a carboxylate type complex. The mechanism of their transoformation is discussed.

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- CoMoO₄ MgO. , 4 : -, , , . .

     

Influence of the oxide matrix on the electronic state of vanadium ions

ESCA spectra of V₂O₅, V₂O₅/TiO₂ and V₂O₅ dissolved in TiO₂ were recorded after oxidation and reduction. V⁴⁺ ions have the same effective charge in reduced V₂O₅ and in TiO₂, whereas the effective charge of V⁵⁺ ions in TiO₂ is higher than in V₂O₅, indicating enhanced electron acceptor properties.

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V₂O₅, V₂O₅ TiO₂ V₂O₅ TiO₂ . , V⁺⁴ V₂O₅ TiO₂ V⁺⁵ TiO₂ V₂O₅, .

     

Electrochemical oxidation of formic acid at noble metals: Catalytic effects of foreign metal monolayers

The catalytic effects of a submonolayer of lead on noble metals have been shown and discussed in terms of a previously published model. A theoretical analysis of these effects is presented. It was demonstrated that foreign metal monolayers allow a determination of the true catalytic activity of electrodes in the case of self-poisoning reactions. A volcano-shaped curve for oxidation of formic acid on noble metal electrodes was obtained.     

Efficient synthesis of 4-aminoquinazoline and thieno[3,2-d]pyrimidin-4-ylamine derivatives by microwave irradiation

[reaction: see text] A simple, efficient, and high-yielding synthesis of quinazolin-4-ylamine and thieno[3,2-d]pyrimidin-4-ylamine derivatives is reported under microwave irradiation conditions. Reaction conditions including temperature, solvent, and reaction time have been studied. An efficient parallel workup procedure was developed to generate a small library (23 compounds) in a short time period.     

Testing equality in lisp-like environments

A function is presented to test equality between lists. In any case the function requires at most one single traversal of the lists and behaves as follows:

1. if there are no cycles, it works as standardEQU AL functions;
2. if there are cycles, it does not give information about equality, but it can detect cycles, i.e. it signals which lists are cyclic.

A simplified version of the function is also considered which is always at least as efficient as standardEQU AL; it grants protection against cycles without signaling them. A coroutine organized version of the function is shown.     

Oxidation of naphthalene on olefin oxidation catalysts

Oxidation of naphthalene on Co–Mo–O, NiMoO₄ and Mg–Mo–O catalysts gives phthalic anhydride, its maximal yield being about 40% on nickel molybdate. On bismuth molybdates and the Sn–Sb–O system, naphthalene is mainly oxidized to carbon oxides.

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Co–Mo–O, NiMoO₄ Mg–Mo–O , ( 40%) . Sn–Sb–O .