Oxidation of primary alcohols to aldehydes with oxygen catalysed by tetra-n-propylammonium perruthenate

The liquid-phase oxidation of a series of saturated and unsaturated non-allylic alcohols to aldehydes with oxygen or air catalysed by tetra-n-propylammonium perruthenate (TPAP, represented as [(n-Pr)₄N]RuO₄) at 80–110 °C is shown to proceed with selectivities of 72–91% at 55–80% alcohol conversion. The unsaturated alcohols, such as 9-decenol, 9-octadecenol and β-citronellol, give the corresponding unsaturated aldehydes without competing double bond attack. The time course of oxidation indicates a complex reaction mechanism. The results on oxidation of a test alcohol, t-Bu(Ph)CHOH, suggest that one-electron processes do not play an important role in the TPAP-catalysed aerobic oxidation of alcohols.     

Thermoconvective instability during electrodialysis

A laser interferometry method is proposed for studying the instability of concentration fields during electrodialysis. It is shown that exceeding the limiting diffusion current density first gives rise to alternating oscillations and then to oscillations at the membrane whose ionogenic groups exhibit the lowest catalytic activity towards the water dissociation reaction. Thereafter, the auto-oscillation process extends over the whole solution volume in the compartments, and dissipative chaos is observed with a further increase in the current density. This instability is presumably a consequence of unevenly distributed heat sources, namely, the Joule heat and the heat of dissociation and recombination of water molecules.     

Acetoxylation of olefins catalyzed by a palladium(II)-heteropolyacid system

The catalytic acetoxylation of ethylene and propylene occurs under the action of oxygen in the presence of Pd(II)+HPA-6, where HPA-6 is the heteropolyacid H₉PMo₆V₆O₄₀. In addition to the products of acetoxylation (alkenyl and allyl acetates), oxidation products (acetaldehyde and acetone) are also formed. The selectivity of acetoxylation increases upon the addition of NaOAc.

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— — Pd(II)+-6, -6 H₉PMo₆V₆O₄₀. (- ) — . NaOAc.

     

Alkylation of p-substituted phenols by heteropoly acids

Liquid-phase alkylation of p-tert-butylphenol (TBP) and p-cresol by olefins and benzyl chloride in the presence of solid heteropoly acids (HPA) H₃PW₁₂O₄₀ and 25% H₃PW₁₂O₄₀/SiO₂ at 100–150°C provides high yields of mono- and disubstituted products. HPAs are more active than H₂SO₄, easily separated from the reaction mixture and can be used repeatedly. -- () - () H₃PW₁₂O₄₀ 25% H₃PW₁₂O₄₀/SiO₂ 100–150°C - - . , H₂SO₄, - - .     

Oxidation of mesitylene by hydrogen peroxide in AcOH-Ac2O-H2SO4

By the oxidation of raesitylene by hydrogen peroxide in AcOH-Ac₂O-H₂SO₄ one can obtain mesitol (2,4,6-trimethylphenol) (with a selectivity of 57–69% at a mesitylene conversion of 22–16% and the acetate of mesitol with a selectivity of 72–85% at 25–22% conversion. The peroxide responsible for the oxidation of mesitylene in this system is in the form of peracetic acid, formedin situ. Over the concentration range studied, the reaction is first order in AcOOH, mesitylene, and H₂SO₄. Hydroxylation of mesitylene by AcOOH proceeds by an electrophilic substitution mechanism, the limiting step being the formation of the -complex.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2716–2721, December, 1990.The authors express their thanks to L. V. Efremova, G. M. Maksimov, and V. D. Chinakov for their assistance in this work.     

p-Type electron transport in La1−xSrxFeO3−δ at high temperatures

Electrical conductivity, thermopower and oxygen content were measured for La_1−xSr_xFeO_3−δ (x=0.2, 0.5, 0.9) within the oxygen partial pressure range 10⁻⁴-0.5 atm and at temperatures 750-950 °C. The dominating charge carriers under these experimental conditions are electron holes. The results of oxygen nonstoichiometry measurements are used to estimate the concentration of holes and to analyze data on conductivity and thermopower. The changes in thermopower are described by the model assuming that the number of sites accessible for migration of holes is independent on oxygen content. The mobility of electron holes is calculated, and it is found to be virtually independent on temperature in the compositions with x<0.5 while compositions with x>0.5 exhibit thermally activated mobility and mobility values about 0.1 cm² V⁻¹ s⁻¹ or smaller. It is suggested that the main contribution to the composition dependent variations in electron hole mobility are associated with Coulomb interactions at small x's, whereas at high degrees of doping the mobility of holes is most strongly affected by the increasing amount of oxygen vacancies.     

Analyticity of the semigroup generated by the operator of a viscous compressible fluid

The linearized initial‐boundary value problem describing small motions of the viscous, barotropic compressible fluid in a bounded vessel is studied under various boundary conditions (Dirichlet, Neumann and intermediate). It is shown that the corresponding operator generates an analytic semigroup in the space L₂. Copyright © 1999 John Wiley & Sons, Ltd.     

Phase of φω interference due to unitarity corrections to the amplitude of φω mixing

The phase of φω interference in the reaction e ⁺ e ^? → π⁺π^?π⁰ near the energy of the φ(1020) peak is calculated within an approach that is virtually independent of the model for φω mixing. A comparison with the phase measured recently (with a poor precision) shows that the deviation of the measured result from the expected value of 180° is associated largely with the effect of the right shoulder of the ω(782) peak in the region of the φ(1020) peak. The ω width at the energy equal to the φ mass is within the interval 120–200 MeV. The effect of the φω-state-induced unitarity corrections to the φ and ω coupling constants on the phase of ρπ interference is considered in detail.