The MM2 force field for silanes and polysilanes

Frierson, Manton R.; Imam, Mita R.; Zalkow, Vera B.; Allinger, Norman L.

doi:10.1021/jo00257a010

Cited by 66 publications

(32 citation statements)

References 6 publications

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“…The longer C2OC3 bond in 1a may suggest a lower s-character at C2, which results in a longer COC3 bond. This is not unreasonable given that Si has a smaller electronegativity than H, C, O, N, or S. Because silicon is more electropositive relative to carbon, when a silicon atom is attached to a C sp 3 O C sp 3 bond it causes an elongation of the C sp 3 OC sp 3 bond [38]. However, in the 1,4-twist conformer (1b) the SiOC bond lengths (1.900 Å) are equal and the C2OC3 bond is shorter (1.545 Å, ⌬r ϭ 0.002 Å) than the C3OC4 bond, and in the 2,5-twist conformer (1c) the SiOC2 bond is longer (1.905 Å, ⌬r ϭ 0.014 Å) than the SiOC6 bond and the C5OC6 bond is longer (1.554 Å, ⌬r ϭ 0.004 Å) than the C2OC3 bond which is longer (⌬r ϭ 0.009 Å) than the C3OC4 bond.…”

Section: Resultsmentioning

confidence: 99%

Relative energies, stereoelectronic interactions, and conformational interconversion in silacycloalkanes

Freeman

Fang

Shainyan

2004

Int J of Quantum Chemistry

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Stereoelectronic hyperconjugative interactions, geometrical parameters, and relative energies of conformations and isomers of silacycloalkanes have been calculated at the B3LYP/6-311ϩG(d,p) level of theory. The chair conformer of silacyclohexane was calculated to be 3.89, 4.82, and 5.18 kcal/mol more stable than the respective 1,4-twist conformer, 2,5-twist conformer, and 2,5-boat transition state. Intrinsic reaction path (IRC) calculations connected the half-chair transition state to the chair and 2,5-twist conformers of silacyclohexane. The energy difference (⌬E) between the chair conformer and the half-chair transition state that connects the chair conformer and 2,5-twist conformer of silacyclohexane is 5.47 kcal/mol. The chair conformer of equatorial 1-methyl-1-silacyclohexane is 0.45 kcal/mol more stable than the chair conformer of axial 1-methyl-1-silacyclohexane. Axial 1-methyl-1-silacyclohexane is 3.53 and 4.67 kcal/mol more than its 1,4-twist and 2,5-twist conformers, and equatorial 1-methyl-1-silacyclohexane is 3.97 and 4.82 kcal/mol more stable than its 1,4-twist and 2,5-twist conformers. 1-Silabicyclo[2.2.1]heptane is 4.58 and 10.8 kcal/mol, respectively more stable than 2-silabicyclo[2.2.1]heptane and 7-silabicyclo[2.2.1]heptane. The influences of selectively replacing a CH 2 group in a cycloalkane with a SiH 2 group on the geometrical parameters, conformational properties, ring strain, and stereoelectronic hyperconjugative interactions are discussed.

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Section: Resultsmentioning

confidence: 99%

Relative energies, stereoelectronic interactions, and conformational interconversion in silacycloalkanes

Freeman

Fang

Shainyan

2004

Int J of Quantum Chemistry

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“…1. 27,28 The experimental kinetics data of the reaction of O ( 3 P) with (CH 3 ) 3 SiH are summarized in Table I. The vibrational frequencies of the reactants, products, and transition states are listed in Table II and Table III.…”

Section: Resultsmentioning

confidence: 99%

Kinetic and mechanistic studies on the abstraction reactions of atomic O (3P) with (CH3)2SiH2 and (CH3)3SiH

Zhang

Wang

2003

The Journal of Chemical Physics

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A theoretical investigation on the mechanism and kinetics for the reaction of atomic O ( 3 P) with CH 3 CHCl 2Theoretical studies on the variational transitional state theory rate constants for the hydrogen abstraction reaction of O ( 3 P) with CH 3 Cl and CH 2 Cl 2 Potential energy surface for the CH 3 + HBr → CH 4 + Br hydrogen abstraction reaction: Thermal and stateselected rate constants, and kinetic isotope effectsThe reactions of atomic O ( 3 P) with (CH 3 ) 2 SiH 2 and (CH 3 ) 3 SiH have been studied theoretically using ab initio molecular orbital theory for the first time. Geometries have been optimized at the MP2 level with the 6-311G(d,p) and 6-311G(2d,2 p) basis sets. The single-point energy calculations have been carried at the QCISD(T)/6-311ϩG(3d f ,2p) level. Theoretical analysis provides conclusive evidence that the main process occurring in each reaction is the hydrogen abstraction from the Si-H bonds leading to the formation of the H 2 and silyl radical; the hydrogen abstraction from the C-H bonds has higher barrier and is difficult to react. Two nearly degenerate transition states of 3 AЉ and 3 AЈ symmetries have been located for each hydrogen abstraction reaction from the Si-H bonds. Changes of geometries, generalized normal-mode vibrational frequencies, and potential energies along the reaction paths are discussed and compared. The rate constants have been deduced over a wide temperature range of 200-3000 K using canonical variational transition-state theory ͑CVT͒ with small curvature tunneling effect ͑SCT͒. The calculated CVT/SCT rate constants exhibit typical non-Arrhenius behavior, three-parameter rate-temperature formulas are fitted as follows ͑in units of cm 3 molecule Ϫ1 s Ϫ1 ): k 1 (T)ϭ(3.41ϫ10 Ϫ16 )T 1.65 ϫexp(Ϫ411.72/T) and k 2 (T)ϭ(1.85ϫ10 Ϫ15 )T 1.42 exp(Ϫ372.57/T) for the reactions of O ( 3 P) with (CH 3 ) 2 SiH 2 and (CH 3 ) 3 SiH, respectively. The calculated rate constants are compared with the available experimental values.

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“…The partial charges on the atoms of these molecules are represented by effective point charges. The parameterization of the potentials for organic chain molecules is adopted from the optimized potentials for liquid simulations (OPLS) force field (Jorgensen et al, 1984(Jorgensen et al, , 1996Stubbs et al, 2001) and the MM2 force field (Frierson et al, 1988).…”

Section: Grand Canonical Simulation Of the Adsorptionmentioning

confidence: 99%

Modeling of Organically Functionalized Mesoporous Silicas for the Design of Adsorbents

Schumacher

Seaton

2005

Adsorption

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In order to obtain atomic-level models for hybrid inorganic-organic adsorbents that are based on ordered mesoporous silicas, molecular simulation methods have been developed which follow the reaction path of the synthesis of the silica material in a kinetic Monte Carlo Simulation. Organic surface groups such as phenyl or aminopropyl are introduced by replacing surface hydroxyl groups. The adsorption in these models is simulated by Grand Canonical Monte Carlo simulation. The experimental and simulated adsorption isotherms of ethane and carbon dioxide on MCM-41-based hybrid adsorbents agree well. In combination, these methods enable the computer-aided design of hybrid inorganic-organic adsorbents.

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The MM2 force field for silanes and polysilanes

Cited by 66 publications

References 6 publications

Relative energies, stereoelectronic interactions, and conformational interconversion in silacycloalkanes

Relative energies, stereoelectronic interactions, and conformational interconversion in silacycloalkanes

Kinetic and mechanistic studies on the abstraction reactions of atomic O (3P) with (CH3)2SiH2 and (CH3)3SiH

Modeling of Organically Functionalized Mesoporous Silicas for the Design of Adsorbents

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