1.Sability to the carbocation through hyperconjugation which is not present in case of benzyl carbocation
2. heteroatoms such as oxygen and nitrogen are more electronegative than carbon, you might expect that they would by definition be electron withdrawing groups that destabilize carbocations.
3. the opposite is often true: if the oxygen or nitrogen atom is in the correct position, the overall effect is carbocation stabilization.
4.This is due to the fact that although these heteroatoms are electron withdrawing groups by induction, they are electron donating groups by resonance, and it is this resonance effect which is more powerful.
Explanation:
1.carbocation becomes more stable as the number of alkyl substituents increases. Carbocations can be given a designation based on the number of alkyl groups attached to the carbocation carbon.
2.Three alkyl groups is called a tertiary (3o) carbocation, 2 alkyl groups is called secondary (2o), and 1 alkyl group is called primary (1o). No alkyl groups are attached (3 hydrogen substituents) is called a methyl carbocation.
3.Resonance effects as a rule are more powerful than inductive effects.electron donation is a resonance effect. Three additional resonance structures can be drawn for this carbocation in which the positive charge is located on one of three aromatic carbons.
4. The positive charge is not isolated on the benzylic carbon, rather it is delocalized around the aromatic structure: this delocalization of charge results in significant stabilization.
5.As a result, benzylic and allylic carbocations (where the positively charged carbon is conjugated to one or more non-aromatic double bonds) are significantly more stable than even tertiary alkyl carbocations.
6.Benzylic carbocations are so stable because they have not one, not two, but a total of 4 resonance structures. This shares the burden of charge over 4 different atoms, making it the most stable carbocation.
