ChemInform Abstract: Stabilization of Positive Charge by β Silicon.

Lambert, Joseph B.; Wang, G.; Finzel, Rodney B.; Teramura, Douglas H.

doi:10.1002/chin.198813079

Cited by 4 publications

(8 citation statements)

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“…The stabilizing effect of positive hyperconjugation increases for stronger σ‐donors. For example, the stabilizing effect of a silyl substituent in β‐silylethyl cation is calculated to be about 38 kcal/mol in the gas phase . Effects of Ge, Sn, and Hg are also substantial; for example, hyperconjugative activation by a Sn–C bond can accelerate a reaction by a factor of >> 10 14 …”

Section: Types Of Hyperconjugationmentioning

confidence: 99%

“…It is well established that such donors as C–Si, C–Ge, and C–Sn bonds are capable of providing significant stabilization to a developing positive charge . For example, Lambert and coworkers reported that axial trimethylsilyl substitution can lead 10 rate enhancements upon elimination of axial leaving groups (Figure ) . The hyperconjugative interaction with the antiperiplanar TMS group was suggested to be responsible for ~10 10 acceleration, with the rest (10 2 ) originating from inductive interactions.…”

Section: Factors Controlling Hyperconjugationmentioning

confidence: 99%

Section: Factors Controlling Hyperconjugationmentioning

confidence: 99%

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Hyperconjugation

Alabugin

Gomes

Abdo

2018

WIREs Comput Mol Sci

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This review outlines the role of hyperconjugative interactions in the structure and reactivity of organic molecules. After defining the common hyperconjugative patterns, we discuss the main factors controlling the magnitude of hyperconjugative effects, including orbital symmetry, energy gap, electronegativity, and polarizability. The danger of underestimating the contribution of hyperconjugative interactions are illustrated by a number of spectroscopic, conformational, and structural effects. The stereoelectronic nature of hyperconjugation offers useful ways for control of molecular stability and reactivity. New manifestations of hyperconjugative effects continue to be uncovered by theory and experiments. This article is categorized under: Structure and Mechanism > Molecular Structures Software > Molecular Modeling Structure and Mechanism > Reaction Mechanisms and Catalysis

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Section: Types Of Hyperconjugationmentioning

confidence: 99%

Section: Factors Controlling Hyperconjugationmentioning

confidence: 99%

Section: Factors Controlling Hyperconjugationmentioning

confidence: 99%

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Hyperconjugation

Alabugin

Gomes

Abdo

2018

WIREs Comput Mol Sci

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“…The stabilizing effect of positive hyperconjugation increases for stronger σ‐donors. For example, the stabilizing effect of a silyl substituent in β‐silylethyl cation is calculated to be ca 38 kcal/mol in the gas phase 97–99. Effects of Ge, Sn, and Hg are also substantial100,101; for example, hyperconjugative activation by a Sn‐C bond can accelerate a reaction by a factor of >10 14,97–99,102…”

Section: Types Of Hyperconjugationmentioning

confidence: 99%

“…It is well established that such donors as CSi, CGe, and CSn bonds are capable of providing significant stabilization to a developing positive charge 131–137. However, the relative ability of many common sigma donors, including the most ubiquitous case of CH versus CC bonds, is still widely debated.…”

Section: Factors Controlling Hyperconjugationmentioning

confidence: 99%

Hyperconjugation

Alabugin

Gilmore

Peterson

2011

WIREs Comput Mol Sci

289

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This review outlines the ubiquitous nature of hyperconjugative interactions and their role in the structure and reactivity of organic molecules. After defining the common hyperconjugative patterns, we discuss the main factors controlling the magnitude of hyperconjugative effects, including orbital symmetry, energy gap, electronegativity, and polarizibility. The danger of underestimating the magnitude of hyperconjugative interactions are illustrated by a number of spectroscopic, conformational, and structural effects. Through the use of advanced computational techniques, the true role of hyperconjugative effects, as it pertains to their influence on stereoelectronics, conformational equilibria, and reactivities relative to other electronic effects, continue to be uncovered.

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3-Substituted-1-(Trimethylsilylmethyl)cyclobutyl Cations: Stereochemistry of Solvent Capture of β-Trimethylsilyl Carbocations

Creary

2023

J. Org. Chem.

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3-tert-Butyl-or phenyl-substituted-1-(trimethylsilylmethyl)cyclobutyl trifluoroacetates react in methanol via β-trimethylsilyl carbocationic intermediates formed from loss of trifluoroacetate ion. These cationic intermediates react to give a significant amount of methyl ether substitution products along with the expected alkene elimination products. Different methyl ether substitution products are formed from isomeric trifluoroacetates, and complete retention of configuration of the ether group relative to the starting trifluoroacetates is observed. The proposed origin of this retention is the involvement of two different β-trimethylsilyl carbocation intermediates that form while utilizing backside participation of the trimethylsilyl group. Computational studies have located three classical 1-(trimethylsilylmethyl)cyclobutyl carbocation energy minima. Two of these cations have a significant barrier (13−16 kcal/mol) to interconversion. It is proposed that methanol can capture each of these cations from different sides, leading to isomeric methyl ether products. A third energy minimum, formed by cyclobutane ring inversion, is thought to be unimportant in determining the stereochemistry of the methyl ether substitution products.

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ChemInform Abstract: Stabilization of Positive Charge by β Silicon.

Abstract: The effects of the leaving group X‐CO‐O‐, the stabilization of the remaining positive charge by SiMe3 and its stereo position, and the substituent R on the rates of elimination of X‐CO‐O‐SiMe3 from (I) to form (II) are studied in detail.

Cited by 4 publications

References 1 publication

Hyperconjugation

Hyperconjugation

Hyperconjugation

3-Substituted-1-(Trimethylsilylmethyl)cyclobutyl Cations: Stereochemistry of Solvent Capture of β-Trimethylsilyl Carbocations

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