what is the stability of aryl carbocations?

Dear rishi,

If the carbon having positive charge is part of a benzene ring, the carbocation is an aryl carbocation.

aryl carbocations do not have resonance stabilisation because their p electron clouds are perpendicular to the vacant p orbital of the carbocation.

Electronegativity is a tendency of electron attraction.  So the stability of a cation is influenced by the electronegativity of the atom bearing the positive charge.  The more electronegative the atom,  less stable the cation.  A vinylic carbocation carrying the positive charge on an sp carbon is more electronegative than an sp² carbon of an alkyl carbocation.  Therefore, a primary vinylic carbocation is less stable than a primary alkyl carbocation. Similar reasoning explains why an aryl carbocation is less stable than a typical secondary alkyl carbocation. Because of their reduced stability, vinyl and aryl carbocations are not discussed often.

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