Akshay Meena
Last Activity: 11 Years ago
Bredt`s rule states that a double bond cannot be placed at the bridgehead of a bridged ring system, unless the rings are large enough (8-Numbered Ring Structure)
Explaination :
Double bond on bridgehead position would be equivalent to having a trans double bond on a ring, which is not possible for small rings (fewer than eight atoms) due to a combination of ring strain, and angle strain (nonplanar alkene). The p orbitals of the bridgehead atom and adjacent atoms are orthogonal and thus are not aligned properly for the formation of pi bonds.
Advantage :
Bredt`s rule can be useful for predicting which isomer is obtained from an elimination reaction in a bridged ring system. It can also be applied to reaction mechanisms that go via carbocations and, to a lesser degree, via free radicals, because these intermediates, like carbon atoms involved in a double bond, prefer to have a planar geometry with 120 degree angles and sp2 hybridization.
Thanks & Regards
Akshay Meena,
askIITians Faculty
M.Tech, IIT Kharagpur