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Bredt's Rule: Understanding Bridgehead Double Bonds

Explore the history and implications of Bredt's Rule discovered by Julius Bredt in 1924, affecting bridged ring systems and double bonds. Learn exceptions and applications in organic chemistry.

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Bredt's Rule: Understanding Bridgehead Double Bonds

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  1. Bredt’s Rule (Ok) (Not happening)

  2. 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

  3. 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

  4. What It Says

  5. H H B r H H H H H 100% What It’s Good For • Good for predicting the product resulting from elimination reactions of bridged ring systems Bredt’s Rule NaOEt EtOH + 110 oC 0%

  6. Exceptions • 8-membered rings with double bonds at the bridgehead can be isolated • Less than 7, extremely difficult to find said character

  7. Exceptions • Anti-Bredt Molecules • 7 membered (or less) rings that do have double bonds located at the bridgehead • Example: 2-quinuclidonium tetrafluoroborate

  8. Exceptions

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