Heteropolyacids as catalysts for synthesis of methyl tert-butyl ether

The influence of the composition and structure of heteropolyacids (HPA) on their catalytic activity in the liquid phase synthesis of methyl tert-butyl ether (MTBE) at 42 °C has been studied. The activity of HPA is compared with that of other acid catalysts. The most active are HPA's of the Dawson structure, then come HPA's of the Keggin and Dexter-Silverton structures. HPA salts have low activity in the synthesis of MTBE.

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() () 42°C. . , -. .

     

The thermodynamic properties of weakly bound oxygen and electron transport in Sr3Fe2O6+δ under oxidizing conditions

The content of oxygen, electrical conductivity, and thermal electromotive force were measured for ferrite Sr₃Fe₂O_6+δ over the oxygen partial pressure range 10^?4–0.5 atm at 650–950°C. The partial molar thermodynamic functions of weakly bound oxygen in the oxide structure were determined. Labile oxygen ions were characterized as an ensemble of weakly interacting particles. The predominant charge carriers under experimental conditions were electron holes. An analysis of conductivity was performed using the data on the oxygen content. The concentration, activation energy, and mobility of charge carriers were determined. The results can be satisfactorily interpreted using the polaron transfer model of conductivity taking into account the charge disproportionation reaction for iron ions, 2Fe⁴⁺ = Fe³⁺ + Fe⁵⁺.     

5-Acylmethyl-3-(2-pyridyl)-1,2,4-triazines: Synthesis and Complexes with Cu(II)

5-Acylmethyl-3-(2-pyridyl)-1,2,4-triazines are easily prepared from accessible 3-(2-pyridyl)-1,2,4-triazine 4-oxides by reaction of the latter with acetophenone or trifluoroacetone in the presence of NaH. The compounds obtained behaved as efficient ligands in reaction with CuCl₂ furnishing dimeric neutral complexes with Cu(II) whose structure was investigated by means of X-ray diffraction analysis.     

KINETICS OF DYNAMIC HOLOGRAM RECORDING IN POLYMER FILMS WITH IMMOBILIZED BACTERIORHODOPSIN

Abstract— Polymer films with immobilized photosensitive membrane protein, bacteriorhodopsin (BR), were prepared and investigated. A sensitive holographic interferometer with phase modulated optical beams was used for investigation of kinetics of dynamic hologram recording in BR polymer films. It was found that phase hologram formation consisted of two quasi-exponential stages demonstrating existence of a diffusive process in obtained films. It was shown that the kinetics of a phase hologram recording by high intensity beams do not correlate with the exponential law. The applicability of BR polymer films as reversible photorefractive materials for dynamic holography and real-time interferometry was discussed.     

An efficient route to 5-(hetero)aryl-2,4′- and 2,2′-bipyridines through readily available 3-pyridyl-1,2,4-triazines

A new route to substituted bipyridines based on a new method for the synthesis of substituted 3-pyridyl-1,2,4-triazines and their aza-Diels-Alder reactions is shown to be an efficient strategy for the preparation of structurally diverse bipyridine ligands.     

Charge states and hyperfine interaction parameters in perovskite SrFeO3

The parameters of the electronic structure and hyperfine interactions in perovskite SrFeO₃ were determined for different types of spin and charge states by ab initio discrete variations within the cluster model. The best agreement with experiment was achieved when the charge disproportionation effect {[Fe⁴⁺O₆]^8? + [Fe⁴⁺O₆]^8?} → {[Fe³⁺O₆]^9? + [Fe⁵⁺O₆]^7?} was taken into account.     

Thermolysis of α-pinene in supercritical lower alcohols

Thermal isomerization of α-pinene in supercritical solvents, viz., ethanol, methanol, and propan-1-ol, was carried out, and differences in the rate and selectivity of the process were revealed. In supercritical ethanol the reaction rate increases sharply and the selectivity remains unchanged with an increase in the temperature (from 290 to 390 °C) or pressure (from 90 to 270 atm). The main reaction products are limonene, isomeric alloocimenes, and pyronenes. The selectivity for limonene in propan-1-ol is higher than in other alcohols when the conversion of α-pinene not higher than 50%. In supercritical ethanol (430 °C, 120 atm, 140 s) limonene is more stable than α-pinene (conversion 8%).