Why are bridge head carbocations unstable?

According to Bredt’s rule a bridgehead carbon atom of bicyclo compound cannot be sp2 hybridised or in other word a bridgehead carbon atom cannot be form double bond. unless the ring that contains at least eight atoms.

For more details on Bredt's rule click here

Related Questions:

Why is cyclopropyl methyl carbocation exceptionally stable?

Which carbocation is more stable : Benzyl or Tertiary?

Trifluoroethyl carbocation is less stable than trifluromethyl carbocation why ?

Which is more stable ,vinyl carbocation or allyl carbocation?

Why is cyclopropyl methyl carbocation exceptionally stable?

The exceptional stability of cyclopropane methyl cation can be explained by the concept of dancing resonance concept. The stability of additional cyclopropyl group , is result of more conjugation between the bent orbital of cyclopropyl ring and cationic carbon.

The most stable carbocation known till date in organic chemistry is explain by Dancing resonance.

Related Questions:

What is dancing resonance or Sigma Resonance or p- orbital resonance ?

What is Bredt's rule ?

Azabicyclo[2,2,1]heptane is more basic thantriethylamine why?.

1-Azabicyclo[2,2,1]heptane is more basic than triethylamine . Because in case of triethylamine the lone pair of electrons is less available in the latter due to rapid nitrogen inversion. Nitrogen inversion is not possible in the bicyclic amine.