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1.
E. L. Kristallovich A. G. Eshimbetov V. M. Promyslov N. D. Chuvylkin L. I. Belen'kii L. V. Molchanov Kh. M. Shakhidoyatov 《Chemistry of Heterocyclic Compounds》2003,39(11):1516-1520
Quantum-chemical calculations and IR spectroscopy were used to study the conformations as well as the energy and spectral characteristics of 2,3-trimethylene- and 2,3-pentamethylene-3,4-dihydro-4-quinazolinones. The shift of -electron density from the heterocyclic system to the carbonyl group and, thus, the proton affinity of the oxygen atom of this group increase with expansion of the bond angle at the nitrogen atom in going from a five-membered to seven-membered ring. 相似文献
2.
A comparative quantum-chemical analysis of the electronic structures and spectroscopic parameters of the cycloalkanes C3H6, C4H8, C5H10, and C6H12 and their silicon analogs Si3H6, Si4H8, Si5H10 and Si6H12 was performed in the framework of the SCF MO LCAO method in the INDO approximation. Qualitative interpretation of “abnormal”
ionization potentials and energies of electronic absorption spectra of cyclopolysilanes has been given.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1105–1108, June, 1997. 相似文献
3.
Based on the MNDO calculations of the electronic structure of the molecules of acrolein, glyoxal, and butadiene, possible mechanisms of the conjugation in systems containing conjugated C=C and C=O bonds have been analyzed. In the electronic ground state ofs-trans-acrolein, the , -conjugation is very small, whereas in the first excited electronic state, the conjugation is substantial, In the ground state ofs-trans-glyoxal, the ,-conjugation should manifest itself clearly but should be weaker than in butadiene, whereas in the first excited electronic state, this conjugation should be more pronounced, Alternation of double and single bonds in the classic structural formula of a molecule does not ensure that this molecule exhibits the properties of a -conjugated system even in planar conformations.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1648–1652, July, 1996. 相似文献
4.
We use tools of the equilibrium statistical mechanics of disordered systems to study analytically the statistical properties of an ecosystem composed of N species interacting via random mutual interactions, as well as via deterministic self-interactions of order p>/=2. We show that the main effect of increasing the order of the interactions among the species is to make the system less competitive, in the sense that the fraction of extinct species is greatly reduced. In addition, we find that for p>2 there is a threshold value which gives a lower bound to the concentration of the surviving species, preventing then the existence of rare species and, consequently, increasing the robustness of the ecosystem to external perturbations. 相似文献
5.
Promyslov V. M. Misurkin I. A. Ovchinnikov A. A. 《Theoretical and Experimental Chemistry》1977,12(5):457-462
Theoretical and Experimental Chemistry - 相似文献
6.
Journal of Structural Chemistry - 相似文献
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8.
Becerra R Boganov SE Egorov MP Faustov VI Krylova IV Nefedov OM Promyslov VM Walsh R 《The journal of physical chemistry. A》2008,112(5):849-857
Time-resolved studies of silylene, SiH2, and dimethylsilylene, SiMe2, generated by the 193 nm laser flash photolysis of appropriate precursor molecules have been carried out to obtain rate constants for their bimolecular reactions with dimethylgermane, Me2GeH2, in the gas phase. SiMe2 + Me2GeH2 was studied at five temperatures in the range 299-555 K. Problems of substrate UV absorption at 193 nm at temperatures above 400 K meant that only three temperatures could be used reliably for rate constant measurement. These rate constants gave the Arrhenius parameters log(A/cm3 molecule(-1) s(-1)) = -13.25 +/- 0.16 and E(a) = -(5.01 +/- 1.01) kJ mol(-1). Only room temperature studies of SiH2 were carried out. These gave values of (4.05 +/- 0.06) x 10(-10) cm3 molecule(-1) s(-1) (SiH2 + Me2GeH2 at 295 K) and also (4.41 +/- 0.07) x 10(-10) cm3 molecule(-1) s(-1) (SiH2 + MeGeH3 at 296 K). Rate constant comparisons show the surprising result that SiMe2 reacts 12.5 times slower with Me2GeH2 than with Me2SiH2. Quantum chemical calculations (G2(MP2,SVP)//B3LYP level) of the model Si-H and Ge-H insertion processes of SiMe2 with SiH4/MeSiH3 and GeH4/MeGeH3 support these findings and show that the lower reactivity of SiMe2 with Ge-H bonds is caused by a higher secondary barrier for rearrangement of the initially formed complexes. Full details of the structures of intermediate complexes and the discussion of their stabilities are given in the paper. Other, related, comparisons of silylene reactivity are also presented. 相似文献
9.
S. E. Boganov V. M. Promyslov S. S. Rynin I. V. Krylova G. S. Zaitseva M. P. Egorov 《Russian Chemical Bulletin》2018,67(3):425-443
Formation of donor-acceptor complexes between dichlorosilylene, SiCl2, and allyl halides, AllHal(Hal= Cl, Br) was detected in Ar matrixes using matrix IR spectroscopy. In agreement with the predictions of the performed quantum chemical calculations, only broad unstructured absorption bands contributed by different conformers of the 1 : 1 complexes between SiCl2 and AllHal were observed in IR spectra of matrixes after deposition in the regions of characteristic vibrations of starting reactants. Annealing of matrixes resulted in strong narrowing the bands due to conversions of different conformers into the most stable structures. The predominantly formed conformers in both the reaction systems were those of complexes with SiCl2 coordinated to the Hal atoms of AllHal in the gauche conformations. At the same time, according to the calculations, the complexes with SiCl2 coordination to the double bonds of AllHal can be only slightly less stable than the complexes with coordination to the Hal atoms, and all these basic centers can be considered as comparable in their activity in the complexation. The only products revealed upon photolysis of complexes were the products of silylene insertion into the C–Hal bonds, viz., AllSiCl3 and AllSiCl2Br. Theoretical study of thermal transformations in the SiCl2 + AllHal systems showed that formal insertion of SiCl2 in the C–Hal bonds and its addition to the double bonds of AllHal have low activation barriers of 3–8 kcal mol–1. However, these barriers are too high for these reactions to occur under the matrix isolation conditions. 相似文献
10.
Kimel" B. G. Tumanov V. V. Faustov V. I. Promyslov V. M. Egorov M. P. Nefedov O. M. 《Russian Chemical Bulletin》2002,51(8):1568-1574
Reactions of a number of germylenes and dimethylsilylene with a phosphaalkene, 2,2-bis(trimethylsilyl)-1-phenyl-1-phosphaethene (1), were studied. The reaction of short-lived dimethylgermylene with 1 produced a phosphagermirane 3 (the first representative of a new class of heterocyclic compounds). Compound 3 was characterized in solution by 1H, 13C, 31P, and 29Si NMR spectroscopy. Subsequent reaction of 3 with dimethylgermylene results in 2,2,3,3-tetramethyl-4,4-bis(trimethylsilyl)-1-phenyl-2,3-digerma-1-phosphacyclobutane 4, which has not been reported so far. In order to rationalize different reactivities of germylenes towards alkenes and phosphaalkenes, the addition products of GeH2 to ethylene and phosphaethene (HP=CH2) were studied using the G2 computational scheme and DFT PBE technique. The adducts of GeMe2 (GeCl2) with HP=CH2 and of GeMe2 with PhP=C(SiH3)2 were also calculated by the DFT PBE method. According to calculations, the exothermicity, DE, of cycloaddition of GeH2 and GeMe2 to the phosphaalkenes HP=CH2 and PhP=C(SiH3)2 (43.5—39.7 kcal mol–1) is nearly twice as high as the exothermicity of cycloaddition of these germylenes to ethylene. In addition to the minimum corresponding to the three-membered cycle, a number of minima corresponding to quite stable donor-acceptor complexes in which the Ge atom is coordinated by the lone electron pair of the P atom in the phosphaalkene molecule were located on the potential energy surface of the germylene—phosphaalkene system. The complexation energy of the complex of GeH2 (GeMe2) with phosphaethene is 25.0 (16.9) kcal mol–1. For GeCl2, the exothermicity of cycloaddition to HP=CH2 decreases to 7.6 kcal mol–1 and the complexation energy decreases to 8.2 kcal mol–1. 相似文献