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11.
Vladimir B. Kobychev Nadezhda M. Vitkovskaya Elena Yu. Larionova Boris A. Trofimov 《Phosphorus, sulfur, and silicon and the related elements》2013,188(12):2931-2940
The ab initio calculations of 1-methoxy-2-propene ( 1 ), 1-methylthio-2-propene ( 2 ), and their anions are performed using the RHF/6-31+G* geometry optimization followed by MP2/6-31+G* energy calculations. Both 1 and 2 are found to rearrange toward 1-substituted 1-propenes with a comparable exothermic effect. However, the proton abstraction energies of 1 and 2 differ significantly. So, the acidity of propene is just slightly affected by the OCH 3 group while the SCH 3 group decreases its proton abstraction energy by 17.5 kcal/mol. Changes in charge distribution, bond lengths and bond orders suggest the negative hyperconjugation to stabilize anions of 2 but not that of 1 . This divergence is explained with a difference in sulfur and oxygen electronegativity. The d -functions of both sulfur and oxygen act in polarization. The Z -isomer of anion 1 is found to be by 2.9 kcal/mol more stable than its E -isomer, this could provide a predominant kinetic formation of the less stable Z -isomer of 1-methoxy-1-propene under base catalysis. 相似文献
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E. Yu. Larionova N. M. Vitkovksaya V. B. Kobychev N. B. Caempf B. A. Trofimov 《Journal of Structural Chemistry》2008,49(4):595-599
The profile of the reaction CH3OH + MOH → CH3OM + H2O in the presence of an alkali (MOH, M = Li, Na, K) was investigated by the ab initio quantum-chemical method for the gas phase (with allowance for the solvent) within the continuum model. The proton transfer and the formation of the alkaline methoxide molecule in MOH/DMSO/CH3OH systems (M = Li, Na, K) in the alkali-methanol pre-reaction complexes can take place without their preliminary dissociation and are barrier-free reactions. 相似文献
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Yu. M. Gavrilyuk A. N. Gangapshev A. V. Derbin I. S. Drachnev V. V. Kazalov V. V. Kobychev V. V. Kuzminov V. N. Muratova S. I. Panasenko S. S. Ratkevich D. A. Tekueva E. V. Unzhakov S. P. Yakimenko 《JETP Letters》2018,107(10):589-594
Resonance excitation of the 83Kr first nuclear level (E = 9.4 keV) by solar axions formed via the Primakoff mechanism is sought. The γ- and X-ray photons and the conversion and Auger electrons arising from the excited-level relaxation are detected with a gas proportional counter of a low-background detector in the underground Baksan Neutrino Observatory. The following experimental constraint is obtained for the product of the axion–photon coupling constant and the axion mass:|gAγ × mA| ≤ 6.3 × 10 -17 In the framework of the hadronic-axion model, this corresponds to a new axion-mass constraint of mA ≤ 12.7 eV at 95% C.L. 相似文献
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Kobychev V. B. Vitkovskaya N. M. Klyba N. S. Trofimov B. A. 《Russian Chemical Bulletin》2002,51(5):774-782
Acetylene—allene rearrangement in propargyl systems XCH2CHCH (X = H, Me, NMe2, OMe, F, and SMe) was studied using the ab initio approach. The relative stabilities of the starting and final propyne structures and the corresponding allenes as well as the structure of intermediate carbanions were considered. n--Conjugation was shown to dominate in allene stabilization while the inductive effect of heteroatomic substituents makes at least comparable contribution to stabilization (or destabilization) of the propynyl structure. In particular, relative instability of 1-methoxypropyne can be rationalized by high electronegativity of O atom, which leads to dramatic decrease in the total electron density in the region of the neighboring CC triple bond. The influence of substituents on the mobility of the migrating proton was considered for the gas phase and with solvation effects included. Calculations involving electron correlation at the MP2 level of theory were shown to be insufficient for correct reproduction of the energy differences between the corresponding propynes and allene structures. The results of MP4 calculations with inclusion of ZPE correction are in good agreement with the available experimental data. 相似文献
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V. B. Kobychev 《Journal of Structural Chemistry》2004,45(1):20-27
Isomerization processes of a double bond site in propene and methylthiopropene molecules with the hydroxide ion were studied in the framework of the RHF/6-31+G*, MP2/6-31+G*, and B3LYP/6-31+G* (density functional) ab initio methods. The solvent effect was taken into account using PCM in its IEFPCM and SCIPCM versions. It is shown that to construct a reaction profile for propene rearrangement, it suffices to perform geometry optimization of stationary points within the Born–Onsager model with further refinement of the energy using IEFPCM. The reaction profiles obtained display that the multiple bond migration mechanism involving the hydroxide ion proton is energetically preferable to the two-stage mechanism forming a solvated carbanion for the propene molecule and for the methylthiopropene molecule that forms a much more stable carbanion. 相似文献
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V. B. Kobychev N. M. Vitkovskaya I. L. Zaitseva E. Yu. Larionova B. A. Trofimov 《Journal of Structural Chemistry》2001,42(4):536-543
The structure and the relative stability of the N-, C-, and C-anions of pyrrole, its mono- and dimethyl derivatives, and their adducts with carbon disulfide were studied by the ab initio method (MP2/6-31+G*//RHF/6-31+G*). The substituent effect on the reaction path is considered. For unsubstituted pyrrole, the stability of the adducts decreases in the series C > N > C. The stability of the N-adducts decreases considerably in the presence of the methyl groups introduced into the -position in view of steric interactions. Possible reasons for the experimentally observed formation of the thermodynamically less stable N-adduct of the unsubstituted pyrrole and for the absence of N-adducts in reactions of the methyl derivatives with CS2 are discussed. 相似文献
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Boris A. Trofimov Ludmila A. Oparina Olga A. Tarasova Alexander V. Artem'ev Vladimir B. Kobychev Yuriy V. Gatilov Alexander I. Albanov Nina K. Gusarova 《Tetrahedron》2014
Superbase-catalyzed (KOH/DMSO suspension as a catalyst) vinylation of hydroxymethyl- and hydroxyethylferrocenes with terminal and internal alkynes (acetylene, propyne, phenylacetylene, 3-ethynylpyridine, 1-propyn-1-yl-benzene, diphenylacetylene) affords hitherto unknown vinyl ethers of ferrocene in 30–93% yields depending on the alkyne structure and the tuneable ratio of reactants/KOH/DMSO. The vinylation smoothly proceeds under mild conditions (70–90 °C, 0.25–13 h). With unsubstituted acetylene the process is readily realized under atmospheric pressure (yield of the corresponding vinyl ethers is 81–90%) though under pressure (initial pressure at room temperature is 10–13 atm, maximum pressure is 13–16 atm at the reaction temperature) the yield is close to quantitative (93%). The synthesized compounds were characterized using 1H and 13C NMR, and IR spectroscopy, as well as X-ray diffraction analysis. 相似文献