Stereochemistry of the formation of 2-alkyl-4,5-dimethyl-1,3,2-dioxaborinanes

It is demonstrated with the help of¹H and¹³C NMR spectroscopy and GLC that the formation of the stereoisomers of 2-alkyl-4,5-dimethyl-1,3,2-dioxaborinanes from 2-methyl-1,3-butanediol and acyclic boric acid esters occurs stereospecifically. This conclusion was confirmed by calculations of the optimal geometries and relative energies of the molecules of thecis-andtrans-isomers of model 4,5-dimethyl-1,3,2-dioxaborinanes and the proposed intermediate with a tetravalent boron atom using the method of molecular mechanics.A. V. Bogatskii Physicochemical Institute, National Academy of Sciences of Ukraine, Odessa 270080, Ukraine. Institute of Organic Chemistry, Ufa Science Center, Russian Academy of Science, Ufa 450054, Russia. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 400–404, March, 1998.     

Effect of intramolecular rotational reorganization of reagents on the ratio between free energies of activation and reaction

Conclusions The relationship between the free energies of activation G and reaction G_o for proton transfer processes have been analyzed, taking into account the effect of hindered rotation of the reagents. We have shown that the considered effect can considerably affect the shape of the G=f(G_o) curve.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 77–81, January 1989.     

Spectral methods in arithmetic problems

Combining ideas of convolution due to Rankin with spectral considerations of Selberg, the author proposes a new approach to obtaining mean values for certain number-theoretic functions f(n). This approach is illustrated for the examples of functions f(n)=(Mn²+N),(n)(Mn+N), where (n) is the number of divisors of n.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova AN SSSR, Vol. 76, pp. 159–166, 1978.     

Synthesis of N,N-dimethylaminoethyl methacrylate copolymers with N-vinyl caprolactam and their complexing and flocculating behavior

Thermosensitive copolymers of N-vinyl carprolactam with N,N-dimethylaminoethyl methacrylate have been synthesized via free-radical polymerization, and reactivity ratios in dioxane have been estimated as 2.44 and 0.07, respectively. It has been shown that temperatures of phase separation for 1% aqueous solutions of homopolymers are close and remain virtually unchanged with the copolymer composition. The efficiency of flocculating behavior of copolymers with respect to a polystyrene latex has been estimated from the initial rate of flocculation as a function of the polyelectrolyte concentration in an acidic medium.     

Reactions of nitrogen oxides (NO,N2O) with the surface of a copper-chromium oxide catalyst

Weight-space and IR spectroscopic methods have been used to investigate the reaction of NO and N₂O with the surface of a copper-chromium oxide catalyst in the form of copper chromite with a 20% excess of Cr₂O₃. Comparisons have been made between the relative reactivities of the different oxides (NO, N₂O, O₂) in oxidation of the Cu⁺ and Cu^o surface centers. The role of these centers in oxidation of CO by oxygen and by nitrogen oxides is discussed.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 21, No. 3, pp. 338–343, May–June, 1985.     

Oxidative addition of N-aminophthalimide to 2-alkenyl-1,3,4-oxadiazoles. Synthesis of aziridinyloxadiazoles

Oxidation of N-aminophthalimide with lead tetraacetate in the presence of 2-[(E)-2-arylethenyl]-5-phenyl-1,3,4-oxadiazoles gives the corresponding 2-(3-aryl-1-phthalimidoaziridin-2-yl)-5-phenyl-1,3,4-oxadiazoles. From 2-phenyl-5-[(1E,3E)-4-phenylbuta-1,3-dien-1-yl]-1,3,4-oxadiazole only the addition product at both C=C bonds was obtained, while in the reaction with 2,5-bis[(E)-2-phenylethenyl]-1,3,4-oxadiazole both mono- and bis-adducts were isolated.     

Influence of the preparation method of precipitated Fe?Mn catalysts on their properties in CO hydrogenation

Studies of the properties of precipitated Fe–Mn catalysts in CO hydrogenation have revealed that samples precipitated from iron and manganese nitrates by sodium carbonate are more selective to olefins than those precipitated by ammonia. Difference in the catalytic properties is due to the different phase compositions of the catalysts.

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