Bredt’s rule relates to bridge heads with carbon-carbon and carbon-nitrogen double bonds. This rule is first discussed by German Scholar Bredt’s in 1902.
What is Bredt’s rule?
According to this rule, a bridge head carbon atom of bicyclo compound cannot be sp2 hybridised or in other word a bridge head carbon atom cannot form double bond, unless the ring contain at least 8 atoms.
In other words, it states that the planarity is not possible at bridge head carbon of bicyclo compound till one of the ring size is having eight atoms or more.
Also, the carbocation on bridge carbon atom is not possible, as it make the carbocation sp2 hybridised.
Here, the stability is possible due to larger ring size of 10 membered carbon ring.
This rule is used for the predicting major and minor product of elimination reactions.
Read More: Unique Guide to Organic Conversions (Cheat Sheet included)