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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.
The Cieplak effect uses hyperconjugation to explain the face-selective addition of nucleophiles to carbonyl carbons. Specifically, donation into the low-lying σ* C-Nuc bond by antiperiplanar electron-donating substituents is the stabilizing interaction which lowers the transition state energy of one stereospecific reaction pathway and thus ...
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 ...
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 .
Cinnamaldehyde is a naturally-occurring compound that has a conjugated system penta-1,3-diene is a molecule with a conjugated system Diazomethane conjugated pi-system. In theoretical chemistry, a conjugated system is a system of connected p-orbitals with delocalized electrons in a molecule, which in general lowers the overall energy of the molecule and increases stability.
The carbon-silicon bond is highly electron-releasing and can stabilize a positive charge in the β position through hyperconjugation. Electrophilic additions to allyl- and vinylsilanes take advantage of this, and site selectivity generally reflects this property—electrophiles become bound to the carbon γ to the silyl group.
In order for the Hofmann product to form, elimination must occur at the 6-position. Because the proton at this position has the correct orientation relative to the leaving group, elimination can and does occur. As a result, this particular reaction produces only the Hofmann product.
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.