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  • 1
    Electronic Resource
    Electronic Resource
    Studies of vacuum pyrolysis of 3-sila- and 3-germa-3,3′-spirobi(6-oxabicyclo[3.1.0]hexanes) and low-temperature matrix stabilization of monomeric silicon dioxide from the gas phase (1993)
    Springer
    Russian chemical bulletin 42 (1993), S. 663-671 
    Details
    ISSN: 1573-9171
    Keywords: vacuum pyrolysis ; matrix IR spectroscopy ; semiempirical method AM1 ; 1,1′-dimethyl-3,3′-spirobi(3-germa-6-oxabicyclo[3.1.0]hexane) ; 1,5-dimethyl-3,3′-spirobi(3-germa-6-oxabicyclo[3.1.0]hexane) ; 1,5-dimethyl-3,3′-spirobi(6-oxa-3-silabicyclo[3.1.0]hexane) ; silicon dioxide ; germanium dioxide ; germanium monoxide ; isopropenyl vinyl ether ; divinyl ether ; 1,3-butadiene ; 2,3-dimethyl-1,3-butadiene ; germanone ; silanone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Vacuum pyrolysis of 3-sila-3,3′-spirobi(6-oxabicyclo[3.1.0]hexanes) leads to the formation of monomeric silicon dioxide and 1,3-butadienes, whereas under the same conditions 3-germa-3,3′-spirobi(6-oxabicyclo[3.1.0]hexanes) afford germanium monoxide, the corresponding divinyl ethers, and 1,3-butadienes. A multistage mechanism of pyrolytic decomposition of the above spirobicyclohexanes was proposed on the basis of experimental data and calculations. The different behavior of the silicon and germanium compounds having similar structures can be explained by an increase in the bivalent state stability and by a decrease in the energy of the metal-oxygen double bond on the transition from silicon to germanium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00703999
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  • 2
    Electronic Resource
    Electronic Resource
    Matrix IR spectra and quantum chemical studies of the reaction between difluorostannylene and hept-1-yne. The first direct observation of a carbene analog π-complex with alkne (1994)
    Springer
    Russian chemical bulletin 43 (1994), S. 47-49 
    Details
    ISSN: 1573-9171
    Keywords: π-complex ; difluorostannylene ; hept-1-yne ; matrix IR spectra ; AM1 ; PM3
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract IR studies of SnF2 and hept-1-yne codeposited in an argon matrix at 12 K has revealed new bands at 540, 565, 1011, 2088 and 3256 cm−1, assigned to the formation of a complex between SnF2 and the alkyne. Quantum chemical AM1 and PM3 calculations confirm this assignment to the π-complex of SnF2 and the triple bond of hept-1-yne, and show that the complex forms without an activation barrier. The energy of the formation of the complex according to AM1 and PM3 calculations is 7.4 and 9.1 kcal/mol, respectively. The calculations indicate that the product of the cycloaddition of SnF2 to a triple bond, stannyrene, is significantly less stable than the π-complex.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00699133
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  • 3
    Electronic Resource
    Electronic Resource
    MNDO method for calculations of magnesium clusters (1994)
    Springer
    Russian chemical bulletin 43 (1994), S. 1310-1314 
    Details
    ISSN: 1573-9171
    Keywords: quantum chemical calculations ; MNDO parameters ; magnesium ; clusters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A new set of parameters for the magnesium atom has been developed within the MNDO method. In contrast to previously published parameters, the new parameters correctly describe molecules with different chemical natures: magnesium halides, organomagnesium compounds and the recently found small magnesium clusters Mg n (n=2-8). The average errors in the calculated heats of formation and bond lengths of magnesium compounds, including clusters are: 10.7 kcal/mol and 0.167 Å, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00703682
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  • 4
    Electronic Resource
    Electronic Resource
    Study of the substituent effect on the activation energy for the dehydrochlorination of chloroalkanes by the MINDO/3 method (1979)
    Springer
    Russian chemical bulletin 28 (1979), S. 1754-1756 
    Details
    ISSN: 1573-9171
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Conclusions 1. The quantum chemical MINDO/3 method, with a variation of all of the independentdegrees of freedom, was used to determine the structures of the starting and end compounds, and also of the transition states, of eight reactions for the dehydrochlorination of chloroalkanes. 2. In contrast to the enthalpies of the reactions, the calculated and experimental activation energies show a good correlation among themselves. 3. The calculations, made without taking into account the effect of substitutents on the structure of the transition state, correctly transmit in a qualitative manner the effect of the substituents on the activation energy; taking these changes into account substantially improves the correlation with the experimental values of the activation energies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00951015
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  • 5
    Electronic Resource
    Electronic Resource
    Reactions of carbonyl compounds in the presence of phase transfer catalysts (1979)
    Springer
    Russian chemical bulletin 28 (1979), S. 1372-1377 
    Details
    ISSN: 1573-9171
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Conclusions 1. Quantum chemical CNDO/BW calculations with optimization of geometries have been carried out on the keto and enol forms of acetone, mesityl oxide, and methyl ethyl ketone, and on the carbanions resulting from various types of deprotonation in these compounds. 2. The keto forms of acetone and mesityl oxide are considerably more stable than the enol forms, while the enolate anions resulting through from heterolytic rupture of the OH bond in the enol forms pass over into the keto form anions with zero activation energy. 3. The calculated gas-phase acidities of the compounds in question here increase in the order: acetone, methyl ethyl ketone, mesityl oxide. 4. Proton detachment from the γ-CH3 group of theβ-form of mesityl oxide, from the secondary C atom of theα-form, or from the hydroxyl group of the enol form leads, in every case, to the same anion structure, namely anα-form carbanion with an unconjugated system of single and double bonds. This, and the anion resulting from proton detachment from theα-methine C atom of theβ-form, are the most stable of the mesityl oxide carbanions. 5. The H atoms bound to the secondary C atom are the most acidic hydrogens in methyl ethyl ketone. Theα-CH3 group acidity is the same in each of the compounds covered by this work.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00947299
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  • 6
    Electronic Resource
    Electronic Resource
    Catalysis in β-elimination reactions. 6. Quantum-chemical calculations on intermediate compounds with correction for solvation in slightly polar solvents (1977)
    Springer
    Russian chemical bulletin 26 (1977), S. 2490-2497 
    Details
    ISSN: 1573-9171
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Conclusions 1. Quantum-chemical calculations by the CNDO/BW and MINDO/2 methods have been carried out on certain modelβ-elimination reactions. 2. Study of various mechanisms involving ion solvation has shown that heterolytic C-H bond rupture is energetically favored over C-OR bond heterolysis, in solution but not in the gaseous phase. 3. In solutions with low dielectric constant (benzene, CH3COOH), ionic mechanisms can be realized only under the action of bases with PA's comparable to that of KOH. 4. Forβ-elimination reactions catalyzed by compounds such as CH3COOH and pyridine, we have proposed nonionic mechanisms based on proton transfer from theβ-carbon atom to the oxygen of the departing alcohol group. 5. It is proposed that the proton solvation energy in low-polarity solvents be calculated by making use of the electrostatic expression for the energy of solvation of the protonated solvent molecule.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00924550
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  • 7
    Electronic Resource
    Electronic Resource
    Quantum-chemical calculations of transition states and activation energies of molecular 1,2-elimination (1,2-addition) of HNO2 (1980)
    Springer
    Russian chemical bulletin 29 (1980), S. 1540-1545 
    Details
    ISSN: 1573-9171
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Conclusions 1. Quantum-chemical calculations of the reactants and the transition states in the reaction of 1,2-addition (1,2-elimination) of HNO2 to a double bond have been carried out. The orbital interactions of the reactants were analyzed, and it was shown that in the course of addition electron density is transferred from HNO2 to the olefin, i.e., HNO2 acts as a nucleophile. 2. The regioselectivity of the addition reaction of HNO2 is determined by the character of the lower vacant MO of the olefin. The addition to nitroethylene should proceed with a lower energy of activation than in the reaction with ethylene, and in opposition to the Markownikoff rule, while the addition to alkyl-substituted ethylene is according to the Markownikoff rule. 3. The introduction of an additional nitro group to the molecule of nitroethane and also replacement of the methyl group in nitroethane by an amino group lead to a considerable decrease in the activation energy of the reaction of the 1,2-elimination of HNO2. 4. The dipole moment of the transition state of the 1,2-elimination of HNO2 is much smaller than in the initial nitroethane, which is explained by mutual compensation of the component due to the polarization of the HNO2-ethylene system and the dipole moment of the HNO2 molecule itself.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00951210
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  • 8
    Electronic Resource
    Electronic Resource
    Quantum-chemical investigation of the mechanism of aldol condensation. Communication 2. Anionic mechanism of condensation and elimination (1982)
    Springer
    Russian chemical bulletin 31 (1982), S. 2201-2206 
    Details
    ISSN: 1573-9171
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Conclusions 1. For the reaction of acetaldehyde with formaldehyde and mixed condensations of formaldehyde with acetaldehyde and acetone, the MINDO/3 method has been used to calculate a section of the potential energy surface of the anionic mechanism of aldol concentration and subsequent dehydration of the aldol that is formed. 2. Conversions of the anions leading to the formation of an aldol and the dehydration of the aldol are accompanied by an increase in the stability of the anions. 3. The direction of mixed condensation of the simplest aldehydes is determined by the CH-acidities of the reacting aldehydes, and this provides for the first time a theoretical interpretation of Liben's rule. 4. The replacement of H atoms in the aldehyde group by CH3 groups, particularly in the carbonyl component, leads to a sharp decrease in the exothermicity of addition and thereby leads to a change in the limiting stage. 5. The reaction pathway including intramolecular isomerization of the aldol anion requires that an additional activation barrier (150 kJ/mole) be overcome, and this pathway cannot be realized unless a catalyst is present.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00958391
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  • 9
    Electronic Resource
    Electronic Resource
    Supra,gauche-[2+2]-cycloaddition and gauche-elimination-symmetry-allowed reactions (1982)
    Springer
    Russian chemical bulletin 31 (1982), S. 2322-2322 
    Details
    ISSN: 1573-9171
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00958429
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  • 10
    Electronic Resource
    Electronic Resource
    Quantum-chemical calculation of reactions involving concerted 1,2 migration of a CH3 group and 1,3(3,1)-H exchange in the propane molecule (1986)
    Springer
    Russian chemical bulletin 35 (1986), S. 1414-1417 
    Details
    ISSN: 1573-9171
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Conclusions 1. Quantum-chemical calculation by the MINDO/3 method revealed the possibility of the occurrence of concerted 1,2 migration of a CH3 group and the less favorable 1,3(3,1)-H exchange in the propane molecule, which proceed through transition states of the pseudocyclopropane type. 2. The discovered principles of model intramolecular rearrangements in two- and threecarbon fragments are in agreement with the known experimental principles of thermocatalytic reactions involving the skeletal isomerization of saturated hydrocarbons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00954814
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