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V. A. Popov S. I. Lopatin L. Sh. Tsemekhman L. A. Pavlinova S. P. Kormilitsyn V. V. Barsegyan 《Russian Journal of Applied Chemistry》2003,76(10):1564-1567
Evaporation of chromium ore and concentrates was studied using high-temperature differential mass-spectrometry. The data obtained, concerning the component vapor pressures in evaporation of complex oxide systems in the range 1700-2100 K, can be used to calculate the evaporation loss in melting and to assess the possibility of utilization of the sublimates formed. 相似文献
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D. S. Barsegyan 《Mathematical Notes》2007,82(3-4):451-460
Applying the method proposed by Kashin for proving inequalities of Lieb-Thirring type for orthonormal systems, we prove a similar inequality in the multidimensional case. 相似文献
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M. Zh. Ovakimyan S. K. Barsegyan A. S. Pogosyan N. M. Kikoyan M. G. Indzhikyan 《Russian Journal of General Chemistry》2006,76(11):1757-1759
Dehydrogenation of 1-(diphenylphosphinoyl)-2-hydrazino-substituted ethanes and N-butyl-N′-phenylhydrazine to the corresponding hydrazone derivatives is performed. Both reactions were established to involve predominantly, if not exclusively, an azo intermediate. 相似文献
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Vera A. Vil' Yana A. Barsegyan Leah Kuhn Maria V. Ekimova Egor A. Semenov Alexander A. Korlyukov Alexander O. Terent'ev Igor V. Alabugin 《Chemical science》2020,11(20):5313
How far can we push the limits in removing stereoelectronic protection from an unstable intermediate? We address this question by exploring the interplay between the primary and secondary stereoelectronic effects in the Baeyer–Villiger (BV) rearrangement by experimental and computational studies of γ-OR-substituted γ-peroxylactones, the previously elusive non-strained Criegee intermediates (CI). These new cyclic peroxides were synthesized by the peroxidation of γ-ketoesters followed by in situ cyclization using a BF3·Et2O/H2O2 system. Although the primary effect (alignment of the migrating C–Rm bond with the breaking O–O bond) is active in the 6-membered ring, weakening of the secondary effect (donation from the OR lone pair to the breaking C–Rm bond) provides sufficient kinetic stabilization to allow the formation and isolation of stable γ-hydroperoxy-γ-peroxylactones with a methyl-substituent in the C6-position. Furthermore, supplementary protection is also provided by reactant stabilization originating from two new stereoelectronic factors, both identified and quantified for the first time in the present work. First, an unexpected boat preference in the γ-hydroperoxy-γ-peroxylactones weakens the primary stereoelectronic effects and introduces a ∼2 kcal mol−1 Curtin–Hammett penalty for reacquiring the more reactive chair conformation. Second, activation of the secondary stereoelectronic effect in the TS comes with a ∼2–3 kcal mol−1 penalty for giving up the exo-anomeric stabilization in the 6-membered Criegee intermediate. Together, the three new stereoelectronic factors (inverse α-effect, misalignment of reacting bonds in the boat conformation, and the exo-anomeric effect) illustrate the richness of stereoelectronic patterns in peroxide chemistry and provide experimentally significant kinetic stabilization to this new class of bisperoxides. Furthermore, mild reduction of γ-hydroperoxy-γ-peroxylactone with Ph3P produced an isolable γ-hydroxy-γ-peroxylactone, the first example of a structurally unencumbered CI where neither the primary nor the secondary stereoelectronic effect are impeded. Although this compound is relatively unstable, it does not undergo the BV reaction and instead follows a new mode of reactivity for the CI – a ring-opening process.Protecting stereoelectronic effects prevent Baeyer–Villiger rearrangement and stabilize γ-OX-γ-peroxylactones (X = H, OH), the previously elusive non-strained Criegee intermediates. 相似文献
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M. Zh. Ovakimyan S. K. Barsegyan N. M. Kikoyan M. G. Indzhikyan 《Russian Journal of General Chemistry》2005,75(7):1069-1073
Triphenyl- and tributyl[2-(2-phenylhydrazino)ethyl]phosphonium salts undergo dehydrogenation on heating to form the corresponding phenylhydrazones in high yields. The phenylhydrazone formed from the triphenylphosphonium salt can also be prepared from triphenyl(1-alkoxy-2-bromoethyl)phosphonium bromides. The latter reaction is proposed to involve reduction of the COC group with phenylhydrazine. N,N-Diphosphonioethylation and N,N-diphosphoniopropylation of hydroxylamine are performed. Alkaline hydrolysis of the resulting diphosphonium salts gave N, N-bis[2-(diphenylphosphoryl)ethyl(propyl)]hydroxylamines in high yields.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 7, 2005, pp. 1132–1136.Original Russian Text Copyright © 2005 by Ovakimyan, Barsegyan, Kikoyan, Indzhikyan. 相似文献
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Ovakimyan M. Zh. Barsegyan S. K. Karapetyan A. A. Panosyan G. A. Indzhikyan M. G. 《Russian Chemical Bulletin》2002,51(9):1744-1747
The reactions of phenylhydrazine and hydroxylamine with (-X-ethyl)triphenylphosphonium salts (X = Ph, Ph3P+Br–) (1, 2) afforded the corresponding -N-ethyl-substituted triphenylphosphonium salts (3, 4). The reaction of triphenyl(2-phenylhydrazinoethyl)phosphonium bromide 3with an aqueous solution of NaOH in benzene afforded a statistical mixture of the nisand transisomers of 2-(diphenylphosphoryl)acetaldehyde phenylhydrazone. (2-Hydroxyaminoethyl)triphenylphosphonium bromide reacted with sodium methoxide to give O-phosphobetaine. 相似文献
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A. G. Barsegyan 《Differential Equations》2012,48(5):756-759
We suggest a constructive method for solving a nonsingular convolution equation with two kernels whose kernel functions are integrable on the entire line. The right-hand side is assumed to be integrable with power p ⩾ 1. 相似文献