29Si NMR study of the surface of pyrogenic silica modified by methylchlorosilanes

Cross-polarization ²⁹Si NMR spectra have been used for aerosil modified by methylchlorosilanes to identify surface organosilicon compounds and their reactions during hydrolysis and methanolysis.Translated from Teoreticheskaya i Eksperimental'naya Khimiya, No. 3, pp. 378–383, May–June, 1986.     

Synthesis of amorphous block copoly(arylene ether ketones) and their characterization

Exchange reactions that may proceed in the course of polycondensation during formation of a polymer from 4,4′-difluorobenzophenone and 4,4′-(isopropylidene)diphenol have been studied. It has been shown that the molecular mass of the polymer decreases under the action of 4,4′-(isopropylidene)diphenol diphenolate. The nucleophilic substitution of the activated aryl halide in DMAA in the presence of potassium carbonate yields high-molecular-mass block copoly(arylene ether ketones) based on 4,4′-difluorobenzophenone and a number of bisphenols. It was demonstrated the synthetic procedure and the chemical structure of block copoly(arylene ether ketones) strongly affect the onset temperature of softening and the mechanical characteristics of the films based on these polymers.     

Intracrystalline diffusion in zeolites

Conclusions A technique for measuring diffusion coefficients for rapid sorption processes has been proposed and applied for studying intracrystalline mass transfer in zeolites.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1217–1219, June, 1981.     

Kinetics of the adsorptional deformation of zeolites

Adsorptional deformation in the Xe-CaA system has been studied at 303 K; the kinetics of adsorption and deformation has been investigated. A kinetic model of deformation is proposed based on the principle of the instantaneous establishment of local deformational equilibrium. Kinetic deformation curves based on this model are plotted that have local extrema above equilibrium values or in the negative region. It is shown that when Xe is adsorbed by CaA zeolite and trans-2-butene is adsorbed by NaA zeolite, the time required for deformational equilibrium to be established is negligibly small, and that deformation at any point of time at any point in the crystal is in equilibrium with respect to adsorption and temperature.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 1948–1951, September, 1990.     

Redox Properties of Rhodium(III) Oxo-Bridged Carboxylate Complexes

Chemical and electrochemical oxidation of rhodium (III) oxo-bridged carboxylate complexes was studied. The chemical [with O₃ and Ce(IV) salts] or electrochemical (at potentials of 1.00-1.20 V) oxidations of the binuclear complexes [Rh₂(-O)(-O₂CCH₃)₂(H₂O)₆]^{2 +} and [Rh₂(-O)(-O₂CCF₃)₂(H₂O)₆]^{2 +} leads to the superoxo complexes [Rh₂(-O)(O₂-)(-O₂CCH₃)₂(H₂O)₅]⁺ and [Rh₂(-O)(O₂ ^-)(-O₂CCF₃)₂(H₂O)₅]⁺ with terminal coordination of O₂-. The trinuclear acetate [Rh₃(₃-O)(-O₂CCH₃)₆(H₂O)₃]⁺, unlike its trifluoroacetate analog [Rh3(₃-O)(-O₂CCF₃)₆(H₂O)₃]⁺, is oxidized only electrochemically at a potential of 1.38 V. The oxidation of [Rh₃(₃-O)(-O₂CCH₃)₆(H₂O)₃]⁺ is reversible and involves formation of an unstable superoxo group O₂ ^- between two Rh₃III(₃-O) cores.     

Reaction between palladium(II) and gallium(III) halogenides in arenes: influence of halogen nature on the formation of binuclear palladium(I) clusters

Palladium(II) bromide reacts with gallium(III) bromide in the presence of arenes yielding binuclear palladium(I) complexes [Pd₂(GaBr₄)₂(arene)₂], where arene=benzene (1), toluene (2) and p-xylene (3). Reaction of palladium(II) chloride with gallium(III) chloride in p-xylene leads to the analogous palladium(I) compound [Pd₂(GaCl₄)₂(p-xylene)₂] (4); the X-ray structures of 1-4 were determined.     

Study of intracrystalline diffusion in zeolites 6. Comparison of the results obtained by the method of densitometry of light and the adsorption method

The use of the method of densitometry of light passing through a layer of zeolite crystals permits determining the limiting stage of diffusion during adsorption by zeolites. Diffusion in transport pores and external heat exchange play the basic role in adsorption of benzene by NaX zeolite, while diffusion in crystals is the determining mechanism of transport in adsorption of water by NaA and NaX zeolites. The diffusion coefficients of water in NaX zeolite have an order of magnitude of 10^–17 m²/sec and increase with an increase in the degree of filling. An explanation for the anomalous behavior of the kinetic adsorption curve for brief times of adsorption of water by zeolite is proposed.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1224–1228, June, 1990.