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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.
Negative hyperconjugation is a theorized phenomenon in organosilicon compounds, in which hyperconjugation stabilizes or destabilizes certain accumulations of positive charge. The phenomenon explains corresponding peculiarities in the stereochemistry and rate of hydrolysis .
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.
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 ...
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 ...
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.
Hyperconjugation can be used to explain phenomena such as the gauche effect and anomeric effect. Orbital symmetry is important when dealing with orbitals that contain directional components like p and d. An example of such an effect is square planar low-spin d 8 transition metal complexes. These complexes exist as square planar complexes due to ...