Niobium-containing catalysts for oxydehydrogenation of hydrocarbons and alcohols

The first methods are developed for introducing niobium(V) into Mg-Al hydrotalcites used as precursors of oxide catalysts for oxydehydrogenation (OD) of alkanes and alcohols. Samples of niobium(V)-containing oxide catalysts are synthesized. Their catalytic properties are studied in oxydehydrogenation of ethane and ethylbenzene to styrene, oxidation dehydrocyclization of octane into ethylbenzene and styrene, and oxydehydrogenation of sec-butanol to ketone (octane-(2)-one). It is ascertained that ethane transformation into ethylene is highly a selective highly process (92–97%) at low temperatures (450–500°C) in the presence of a niobium-containing catalyst; the catalyst is appreciably efficient in ethylbenzene transformation to styrene and dehydrocyclization of n-octane to ethylbenzene and styrene, and in oxydehydrogenation of secbutanol to octane-(2)-one. All the catalysts studied operate stably in OD reactions; no decrease in their activity or selectivity was detected after 50 h operation.     

Influence of hydrothermal conditions on the phase transformations of amorphous alumina

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Reactive Hydrogel Networks for the Fabrication of Metal–Polymer Nanocomposites

In this study, highly stable gold and silver nanoparticles evenly distributed within a crosslinked poly(acrylamide)/poly(N‐(hydroxymethyl)acrylamide) (PAAm‐PHMAAm) network have been fabricated without addition of a reducing agent. Remarkably, the same chemical hydrogel composition has been involved in the successful fabrication of spherical gold and silver nanoparticles within the hydrogel template. The hydrogel network acts simultaneously as an efficient reducing agent and stabilizer. The PAAm–PHMAAm hydrogel network binds metal ions and, following reduction of bound to crosslinked template metal ions, proceeds via oxidation of hydroxymethyl hydrogel fragments. A one‐electron mechanism is proposed for the formation of the silver and gold nanoparticles.

     

[Tri(tert-butoxy)silyl]methylmagnesium chloride

A reaction of potassium tert-butoxide with chloromethyltrichlorosilane in THF leads to tri(tert-butoxy)chloromethylsilane. Upon reflux in THF, it reacted with magnesium with the formation of stable [tri(tert-butoxy)silyl]methylmagnesium chloride, whose structure was confirmed by ¹H, ¹³C, and ²⁹Si NMR spectroscopy. In the THF solution at 25 °C, [tri(tert-butoxy)silyl]methylmagnesium chloride exists in the equilibrium with bis{[tri(tert-butoxy)silyl]methyl}magnesium (in the ratio of 1: 1).     

Reaction products of nitronyl nitroxyl radicals with acids

Study of the structures of compounds generated by the reactions of 4,4,5,5-tetramethyl-2-phenyl-4,5-dihydro-1H-imidazole-1-oxyl 3-oxide with trifluoromethanesulfonic and picric acids demonstrated that these reactions produced salts of disproportionation products of nitronyl nitroxyl.     

Formation of Exciplexes in Films of Polyimides,Polyamides, and Polyquinazolones Derived from Aromatic and Heteroaromatic Diamines

The emission bands exchibited by films of polyimides derived from 1,3-bis(3,4-dicarboxyphenoxy)benzene dianhydride, hexafluoroisopropylidenedibenzene-3,3′,4,4′-tetracarboxylic dianhydride, and aromatic and heteroaromatic diamines, and also of polyamides and polyquinazolones derived from the same amines are exciplex bahnds. With polyamides, complexes in the ground state are formed. The fluorescence of the photoconductivity sensitizer Rhodamine 6G is quenched in films of these polymers by the exciplex mechanism.     

Synthesis and Structure of Diisopropyl 6-Hydroxy-6-methyl-4-oxocyclohexane-1,3-dicarboxylates and Their Reactions with Nucleophilic Reagents

Base-catalyzed reactions of isopropyl acetoacetate with aromatic and heterocyclic aldehydes afforded the corresponding diisopropyl 6-hydroxy-6-methyl-4-oxocyclohexane-1,3-dicarboxylates which were brought into reactions with mono- and difunctional nitrogen-containing nucleophiles. According to the X-ray diffraction data, diisopropyl 4-oxocyclohexane-1,3-dicarboxylates in crystal exist in the ketone form.__________Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 7, 2005, pp. 1039–1045.Original Russian Text Copyright © 2005 by Gein, Nosova, Potemkin, Aliev, Kriven’ko.