SciTechDaily;

UCLA chemists have discovered a major flaw in a fundamental rule of organic chemistry that has held for 100 years. They say it’s time to rewrite the textbooks.

Organic molecules, which are primarily made of carbon, have specific shapes and arrangements of atoms. Molecules called olefins contain double bonds, or alkenes, between two carbon atoms. Typically, these atoms and their attached groups lie in the same 3D plane, and deviations from this structure are rare.

The rule being questioned, known as Bredt’s rule, was established in 1924. It asserts that molecules cannot have a double bond at the “bridgehead” position—the junction of a bridged bicyclic molecule—because this position would distort the geometry of the double bond. Bredt’s rule has constrained the design of synthetic molecules by preventing chemists from creating certain structures. Since olefins play a critical role in pharmaceutical research, Bredt’s rule has limited the types of molecules that scientists could envision, potentially holding back innovations in drug discovery.

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