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Hyperconjugation can be used to rationalize a variety of chemical phenomena, including the anomeric effect, the gauche effect, the rotational barrier of ethane, the beta-silicon effect, the vibrational frequency of exocyclic carbonyl groups, and the relative stability of substituted carbocations and substituted carbon centred radicals, and the thermodynamic Zaitsev's rule for alkene stability.
Hyperconjugation model for explaining the gauche effect in 1,2-difluoroethane. Key in the bent bond explanation of the gauche effect in difluoroethane is the increased p orbital character of both C−F bonds due to the large electronegativity of fluorine. As a result, electron density builds up above and below to the left and right of the ...
The Cieplak effect relies on the stabilizing interaction of mixing full and empty orbitals to delocalize electrons, known as hyperconjugation. [2] When the highest occupied molecular orbital of one system and the lowest unoccupied molecular orbital of another system have comparable energies and spatial overlap, the electrons can delocalize and sink into a lower energy level.
The α- and β-anomers of D-glucopyranose.. In organic chemistry, the anomeric effect or Edward-Lemieux effect (after J. T. Edward and Raymond Lemieux) is a stereoelectronic effect that describes the tendency of heteroatomic substituents adjacent to a heteroatom within a cyclohexane ring to prefer the axial orientation instead of the less-hindered equatorial orientation that would be expected ...
Hyperconjugation model for explaining the gauche effect in 1,2-difluoroethane There are two main explanations for the gauche effect: hyperconjugation and bent bonds . In the hyperconjugation model, the donation of electron density from the carbon–hydrogen σ bonding orbital to the carbon–fluorine σ * antibonding orbital is considered the ...
Free-radical intermediate is stabilized by hyperconjugation; adjacent occupied sigma C–H orbitals donate into the electron-deficient radical orbital. A new method of anti-Markovnikov addition has been described by Hamilton and Nicewicz, who utilize aromatic molecules and light energy from a low-energy diode to turn the alkene into a cation ...
This phenomenon, a type of resonance, can stabilize the molecule or transition state. [2] It also causes an elongation of the σ-bond by adding electron density to its antibonding orbital. [1] Negative hyperconjugation is seldom observed, though it can be most commonly observed when the σ *-orbital is located on certain C–F or C–O bonds ...
Stabilization is possible because of a good overlap between the C-H bond and the empty p-orbital at C a. Hyperconjugation is evident in all structures because of the adjacent C b-H bond and in the –CH 3 substituent. Enthalpy calculations obtained from the isodesmic reaction are fair accurate and shows good correlation with experimental data.