Emily Chan
In the early 20th century, a German chemist named Julius Bredt studied double bonds in bicyclic molecules, which are a group of chemicals that contain two ring-shaped structures attached together.
The shape of these bicyclic molecules looks something like a three-dimensional Y-shaped structure. According to Bredt’s rule, based on his observations in the lab, carbon atoms next to the “Y” junctions cannot form double bonds.
Since the carbon near the Y-shaped bridges and its surrounding atoms are not all in the same plane, Bredt believed that a double bond at the bridgehead position would make the molecule too unstable to exist.
But now, a team of chemists from the University of California, Los Angeles, have broken this 100-year-old chemistry rule by synthesizing a class of molecules that were thought to be too unstable to form.
The “anti-Bredt” molecules violate Bredt’s rule. They could help further drug research and allow scientists to make new kinds of medicine.
“If there’s a rule that says something is absolutely impossible, then maybe you just haven’t thought of the right way of solving it. And if you do it, it actually might not be as difficult as you think,” said Luca McDermott, the first author of the study and an organic chemist at UCLA.
The anti-Bredt molecules belong to a class of compounds called olefins, which have at least one double bond connecting two carbon atoms.
A double bond is a strong chemical bond made from two pairs of electrons. Each of the carbon atoms is usually present in the same two-dimensional plane as the other atoms they’re bonded to.
McDermott and colleagues figured out how to make anti-Bredt olefins and are using the method to synthesize complex three-dimensional molecules.
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