Formation and decay of the dehydrogenated parent anion upon electron attachment to dialanine

The dehydrogenated parent anion [M-H](-) is one of the most dominant anions formed in dissociative electron attachment to various small biomolecules like nucleobases and single amino acids. In the present study, we investigate the [M-H](-) channel for the dipeptide dialanine by utilizing an electron monochromator and a two-sector-field mass spectrometer. At electron energies below 2?eV, the measured high-resolution ion-efficiency curve has a different shape to that for the single amino acid alanine, which is explained by the altered threshold energies for formation of [M-H](-) determined in quantum chemical calculations. Moreover, the structure of the formed [M-H](-) anion is further studied by investigating the unimolecular and collision-induced decay of this anion. Trajectory calculations have been carried out to aid the interpretation of the experimentally observed fragmentation patterns.     

Catalytic properties of Sn-Ce-Rh-O in dehydrogenation and oxidative dehydrogenation reactions

A new, single-phase Sn_0.925Ce_0.07Rh_0.005O₂ gas sensitive material has up to now been used as a catalyst for the bimolecular condensation of aldehydes and C-alkylation of hydroxyarenes with alcohols. It was subjected to the isopropanol test, the oxidative dehydrogenation of cyclohexane test, and the cyclohexene + H₂ test. A general physico-chemical analysis was done, and it included XRD, SEM, mercury porosimetry, TPD NH₃, and IR (pyridine) spectroscopy. The tests results are compliant with the basic character of the catalyst; however, it reveals significant total acidity (0.274 mmol NH₃/g) and the presence of Lewis strong acid centers (0.126 mmol Py/g). The presence of these centers in the dehydrogenating catalysts cause the ability to catalyze both the bimolecular condensation of aldehydes and C-alkylation of hydroxyarenes with alcohols. Published in Russian in Kinetika i Kataliz, 2007, Vol. 48, No. 1, pp. 74–80. The article was submitted by the authors in English.     

Influence of styrene on the oxidative dehydrogenation of ethylbenzene

The influence of styrene and by-products of side reactions on the oxidative dehydrogenation of ethylbenzene into styrene with use of the vanadia-magnesia catalyst has been investigated. Notable slowing-down influence of styrene contained in the substrates on the process has been ascertained, whereas the contamination with other products has not caused such an effect. The apparent activation energy and pre-exponential factor for the investigated reactions were calculated.     

Electrochemical modeling of the oxidative dehydrogenation of 4H-thiopyrans

The oxidation of substituted 4H-thiopyrans on a rotating platinum disk electrode with a ring in acetonitrile was accomplished for the first time. It was established that the dehydrogenation of both tri- and pentasubstituted thiopyrans proceeds via a scheme involving the successive transfer of an electron, a proton, and an electron (an EPE process); 4H-thiopyrans are oxidized more readily than the corresponding oxygen analogs.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 318–320, March, 1984.     

Tungsten-containing catalysts for oxidative dehydrogenation of hydrocarbons

Methods for introducing tungsten into the precursors of oxide catalysts for oxidative dehydrogenation (OD) were developed. Tungsten-containing samples of oxide catalysts of various compositions were synthesized and their catalytic properties in OD of ethane were studied. The introduction of tungsten into the catalysts increased the yield of ethylene in all cases. In the series of tungsten-containing catalysts, the ethylene yield increased in the following order of the catalysis: Mg-Al-V-Mo-W-O < Mg-Al-Ni-V-Mo-W-O < Mg-Al-Fe-V-Mo-W < Mg-Al-Cr-V-Mo-W-O.     

Copper-containing catalysts for the oxidative dehydrogenation of organic compounds

A method of doping magnesium aluminum hydrotalcites, which are precursors for oxidative dehydrogenation oxide catalysts of various compositions, with copper(II) was developed, and copper(II)-containing oxide catalyst samples were synthesized. The catalytic properties of these catalysts were studied in the oxidative dehydrogenation of ethane, propane, and hexane. The conversion of ethane into ethylene on the copper-containing catalysts was established to proceed with high selectivities (90?C97%) and at low temperatures (400?C450°C).     

Boron nitride for enhanced oxidative dehydrogenation of ethylbenzene

It is demonstrated experimentally and confirmed theoretically that highly defective boron nitride showed outstanding performance for oxidative dehydrogenation o...     

Indium-containing catalysts for oxidative dehydrogenation of organic compounds

For the first time, a method was developed for introducing indium into Mg-Al hydrotalcites—precursors of oxide catalysts for oxidative dehydrogenation of alkanes. Samples of oxide catalysts were synthesized that contained indium oxide and also oxides of magnesium, aluminum, chromium, vanadium, molybdenum, and niobium in various combinations. The catalytic properties of the produced catalysts were studied in the oxidative dehydrogenation of ethane, propane, and isobutane. It was established that the introduction of indium into catalysts increases the selectivity and the yields of desired products. New hydroxo salts with a layered structure of the hydrotalcite type were synthesized: [Al_{1 ? n} In _n Mg _m (OH)_{3 + 2m ? 1}][(NO₃) · nH₂O] and quaternary magnesium indium chromium aluminum hydroxonitrate of the composition [Al_0.5In_0.5Cr_0.5Mg_2.5(OH)_8.5][(NO₃) · nH₂O]; these salts were found to be isostructural. The obtained compounds were studied as catalyst precursors.     

Efficient aerobic oxidative dehydrogenation of dihydropyrimidinones and dihydropyrimidines

4-Substituted dihydropyrimidinones and dihydropyrimidines were first efficient aerobic oxidized to the corresponding pyrimidinones and pyrimidines, respectively, in high yields by molecular oxygen in the presence of catalytic amount of N-hydroxyphthalimide (NHPI) and Co(OAc)₂ in a mild and environmental benign condition.     

Gallium-containing catalysts for oxidative dehydrogenation of organic compounds

A method was developed for introducing gallium into Mg-Al hydrotalcites—precursors of oxide catalysts for oxidative dehydrogenation of alkanes. Samples of oxide catalysts were synthesized that contained gallium oxide and also oxides of magnesium, aluminum, chromium, vanadium, molybdenum, and niobium in various combinations. The catalytic properties of the produced catalysts were studied in the oxidative dehydrogenation of ethane, propane, isobutane, and hexane. It was established that the addition of gallium to catalysts increases the ethylene and propylene yields in the oxidative dehydrogenation of ethane and propane. New hydroxo salts with a layered structure of the hydrotalcite type were synthesized: ternary magnesium gallium aluminum hydroxonitrate of variable composition [Al_{1 ? n} Ga _n Mg _m (OH)_{3 + 2m ? 1}][NO₃ · nH₂O] and quaternary magnesium gallium chromium aluminum hydroxonitrate of the composition [AlGaCrMg_1.8(OH)_11.6][NO₃ · nH₂O]; these salts were found to be isostructural.     

Praseodymium-containing catalysts for oxidative dehydrogenation of organic compounds

A method is developed for incorporating praseodymium into magnesium–aluminum hydrotalcites, which are precursors for oxide catalysts for oxidative dehydrogenation (ODH) of alkanes. Oxide catalyst samples that contain praseodymium and various combinations of magnesium, aluminum, chromium, vanadium, molybdenum, and niobium are prepared. The catalytic properties of the prepared catalysts in ethane, propane, and butane ODH reactions are studied. Into some of our studied multicomponent catalysts, the incorporation of praseodymium enhances the reaction selectivity and increases yields of desired products.     

GRAPH-topological study of adamantanes

Topological characteristics of some structural analogs of adamantanes are calculated. Correlations are studied between the Wiener indices and the experimental chromato graphic retention indices as well as the calculated molecular volumes, hydration energies, and distribution coefficients in an n-octanol water system for the title compounds. Translated from Zhurnal Strukturnoi Khimii, Vol. 41, No. 4, pp. 805-812, July-August, 2000.