DFT, NBO, and NRT analysis of alkyl and benzyl β-silyl substituted cations: carbenium ion vs. silylium ion

Dabbagh, Hossein A.; Zamani, Mehdi; Fakhraee, Sara

doi:10.1007/s11164-012-0483-3

Cited by 10 publications

(6 citation statements)

References 50 publications

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“…53 The carbonsilicon bond is anti-periplanar to the developing carboncarbon bond, which would be expected because of stabili-zation of the incipient carbocationic center by the carbonsilicon σ-bond. 54,55 The calculated energy differences between the inside and outside attack modes are consistent with the selectivities observed for formation of the major products 20 and 21 at −78 °C. The difference in energies for the oxepane-fused oxocarbenium ion is lower than for the cycloheptane-fused system, which is in accord with the experimental results.…”

Section: ð4þsupporting

confidence: 78%

“…Critical parameters, such as the length of the developing carbon–carbon bond (ranging between 2.4 and 2.5 Å), agree with values obtained from transition structures identified for allylation of propargylic cations 53 . The carbon–silicon bond is anti-periplanar to the developing carbon–carbon bond, which would be expected because of stabilization of the incipient carbocationic center by the carbon–silicon σ-bond 54,55 .…”

Section: Discussionmentioning

confidence: 95%

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Effect of conformational rigidity on the stereoselectivity of nucleophilic additions to five-membered ring bicyclic oxocarbenium ion intermediates

2014

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Nucleophilic substitution reactions of five-membered ring acetals bearing fused rings reveal that subtle changes in the structure of the fused ring can exert dramatic influences on selectivity. If the fused ring did not constrain the five-membered ring undergoing substitution, selectivity was comparable to what was observed for an unconstrained system (≥92% diastereoselectivity, favoring the product of inside attack on the oxocarbenium ion). If the ring were more constrained by including at least one oxygen atom in the ring, selectivity dropped considerably (to 60% diastereoselectivity in one case). Transition states of the nucleophilic addition of allyltrimethylsilane to selected oxocarbenium ions were calculated using DFT methods. These computational models reproduced the correlation between additional conformational rigidity and selectivity.

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Section: ð4þsupporting

confidence: 78%

Section: Discussionmentioning

confidence: 95%

Effect of conformational rigidity on the stereoselectivity of nucleophilic additions to five-membered ring bicyclic oxocarbenium ion intermediates

2014

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“…There is also a rich literature on silicon substituted carbocations, and cross method evaluations have been recently published on these systems (Fernandez and Frenking, 2007 ; Dabbagh et al, 2012 , 2013 ). Still on carbocations, Schleyer et al very recently (Wu and Schleyer, 2013 ), showed large hyperconjugation effects in various strained systems.…”

Section: Introductionmentioning

confidence: 99%

Hyperconjugation in Carbocations, a BLW Study with DFT approximation

Alamiddine

Humbel

2014

Front. Chem.

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The geometry of ethyl cation is discussed, and the hyperconjugation effect in carbocations is evaluated at the B3LYP/6-311G(d) level. The Block Localized Wavefunction (BLW) method is used for all evaluations of the hyperconjugation, considered as the energy gained by the delocalization onto the C+ atom. This energy is defined as the energy difference between the delocalized (standard) calculation, where the electrons are freely delocalized, and a localized form where the positive charge sits on the carbon center. It is evaluated for 18 carbocations, including conjugated systems. In these cases we were particularly interested in the additional stabilization brought by hyperconjugative effects. Among other effects, the β-silicon effect is computed. Hyperconjugation amounts in several cases to an energy similar to conjugation effects.

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“…). Recently, Dabbagh et al and others have reported large stabilization energy for antibonding interactions (π * → σ * , π * → π * , π * → LP * , LP * → σ * , and LP * → π * ). These orbitals have relatively high occupancy and their interactions are favored by energy and symmetry factors .…”

Section: Resultsmentioning

confidence: 99%

“…5). Recently, Dabbagh et al [102][103][104][105] and others [106][107][108] have reported large stabilization energy for antibonding interactions (p * ! r * , p * !…”

Section: Charge-transfer Analysis Of Endohedral X@b 20 O 30 Nanocapsulesmentioning

confidence: 99%

Gas storage of simple molecules in boron oxide nanocapsules

Zamani

Dabbagh

Farrokhpour

2013

Int. J. Quantum Chem.

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The capability of the B20O30 nanocapsule to store H2, N2, CO, CO2, NH3, CH4, and Cl2 molecules on the outer surface and inside of the cage was investigated using Monte Carlo simulations, long‐range and dispersion corrected density functional theory, and Møller–Plesset second‐order perturbation theory. Also, Monte Carlo simulations were employed to investigate the adsorption behavior of larger number of guest molecules inserted into and onto the larger B80O120 and B20O30@B80O120 cages. Absolute localized molecular orbitals energy decomposition analysis was used to describe the nature of intermolecular interactions in these endohedral and exohedral complexes. It is found that the hydrogen and ammonia gases are diffused to the inside of spherical B20O30 capsule, while other guest molecules prefer to interact with the outer surface of spherical and pyramidal capsules. For B80O120, up to 26 H2 and 11–14 N2, CO, CO2, NH3, and CH4 molecules are stored inside the capsule. The residual molecules are adsorbed on the outer surface of nanocapsule. © 2013 Wiley Periodicals, Inc.

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DFT, NBO, and NRT analysis of alkyl and benzyl β-silyl substituted cations: carbenium ion vs. silylium ion

Cited by 10 publications

References 50 publications

Effect of conformational rigidity on the stereoselectivity of nucleophilic additions to five-membered ring bicyclic oxocarbenium ion intermediates

Effect of conformational rigidity on the stereoselectivity of nucleophilic additions to five-membered ring bicyclic oxocarbenium ion intermediates

Hyperconjugation in Carbocations, a BLW Study with DFT approximation

Gas storage of simple molecules in boron oxide nanocapsules

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