Bredt’s Rule
(Ok)
(Not happening)
History and Background
• Discovered in 1924 by
Julius Bredt while
investigating the chemistry
of naturally occurring
bicyclic terpenes
• He’s German
• Bredt also was the first to
determine the structure of
camphor (1893)
– Camphor contains a bridged
ring
What It Says
• You can’t have a double bond connected to
the bridgehead of a bridged ring system
– UNLESS the ring is big enough
• Having a double bond as part of the
bridgehead would be the equivalent of
having a trans double bond on the ring
– This would create massive angular strain on
the ring
What It Says
What It’s Good For
• Good for predicting the product resulting from elimination
reactions of bridged ring systems
Bredt’s
Rule
H
Br
H
H
H
H
NaOEt
+
EtOH
110 oC
100%
H
0%
H
Exceptions
• 8-membered rings with double bonds at the
bridgehead can be isolated
– Less than 7, extremely difficult to find said character
Exceptions
• Anti-Bredt Molecules
– 7 membered (or less)
rings that do have
double bonds located
at the bridgehead
– Example: 2quinuclidonium
tetrafluoroborate
Exceptions