Sigma-Bond Metathesis

Sigma-Bond Metathesis-7
It has been suggested that dehydrocoupling reactions proceed via sigma-bond metathesis.

Carbon–hydrogen bond activation Carbon–hydrogen bond functionalization (C–H functionalization) is a type of reaction in which a carbon–hydrogen bond is cleaved and replaced with a carbon-X bond (where X is usually carbon, oxygen, or nitrogen).

The term usually implies that a transition metal is involved in the C-H cleavage process.

"sigma bond metathesis for C-H bonds of hydrocarbons and Sc-R (R = H, alkyl, aryl) bonds of permethylscandocene derivatives.

system in electrophilic activation of aromatic and vinylic C-H bonds".

Misconception: many students after drawing such electron dot diagrams fail to appreciate that in reality molecules exist as a 3D system and not as a two dimensional system as shown above.

These diagrams are drawn for simplicity and should not be viewed as an exact representation of what a molecule looks like.Indeed, the rate of the reaction is characterized by a highly negative entropy of activation, indicating an ordered transition state.For metals unsuited for redox, sigma bond metathesis provides a pathway for introducing substituents.The timestamp is only as accurate as the clock in the camera, and it may be completely wrong.In organometallic chemistry, sigma-bond metathesis is a chemical reaction wherein a metal-ligand sigma bond undergoes metathesis (exchange of parts) with the sigma bond in some reagent.system in electrophilic activation of aromatic and vinylic C-H bonds has been examined. A picture of the transition state for such sigma-bond metathesis reactions is developed, which accounts for the relative reactivities of sp-, sp/sup 2/-, and sp/sup 3/-hybridized C-H bonds with Cp*/sub 2/Sc-R (R = H, alkyl, aryl). sigma bond metathesis for C-H bonds of hydrocarbons and Sc-R (R = H, alkyl, aryl) bonds of permethylscandocene derivatives. system in electrophilic activation of aromatic and vinylic C-H bonds. Misconception: many students in the Pacific may have this wrong notion that a sigma bond is the result of the overlapping of s orbitals and a pi bond is the result of the overlapping of p orbitals because they may relate the 's' to 'sigma' and the 'p' to 'pi'.However, it is seen that sigma bonds can be formed by the overlapping of both the s and p orbitals and not just s orbital.

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