CARBOCATION FORMATION AND CARBOCATION STABILITY ORDER


Carbocation definition 

Carbocation is the intermediate of carbon containing positive charge. It has six electrons in the valence shell.

Carbocation formation 

Carbocation is formed by the heterolytic bond fission between C-X in an organic compound.If X is more electronegative than carbon , the former takes away the bonding electron pair and becomes negatively charged. And carbon becomes positively charged (carbocation).

Carbocation hybridization

       Hybridization of C+ = sp2
       Geometry of C+ = Trigonal Planar

 
Carbocation stability order: 

There are three factors contributing to the stability of carbocations:

   (a)  Inductive Effect 
   (b) Hyperconjugation 
   (c) Resonance
(a) Inductive Effect: The carbocation is stabilized by ERG and destabilized by EWG.

   
 

(b) Hyperconjugation: The positive charge is delocalized over α-H atoms and the octet of the C carrying positive charge is completed.


   (c) Resonance: Resonance is a stabilizing factor as it delocalizes the positive charge and therefore provides stability.


Both these carbocations are very highly stable due to resonance.




 
Both vunyl and phenyl carbocations are highly unstable. resonance is absent as there is no conjugation between pie electrons  and positive charge.

Orbital Picture of Vinyl Carbocation :
 

The empty ‘p’ orbital is perpendicular to the ‘p’ orbitals forming the p bond.


Orbital Picture of Phenyl Carbocation





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