Chemistry

Chemists say it’s time to break 100-year-old rules and rewrite textbooks

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Chemists at UCLA have discovered a big problem with the basic rules of organic chemistry that have existed for 100 years. That’s not true at all. And they say, “It’s time to rewrite the textbooks.”

Organic molecules are primarily composed of carbon and are characterized by having a specific shape and arrangement of atoms. Molecules known as olefins have a double bond, or alkene, between two carbon atoms. An atom and its bonded atoms usually lie in the same 3D plane. Molecules that deviate from this geometry are rare.

The rule in question, known in textbooks as Bred’s Law, was reported in 1924. This rule states that a molecule cannot have a carbon-carbon double bond at the ring junction (also known as the “bridgehead” position) in a bridged bicyclic molecule. These structural double bonds likely had a distorted and twisted geometry that deviated from the rigid geometry of alkenes taught in textbooks.

Although olefins are useful in pharmaceutical research, Bred’s law has limited the types of synthetic molecules that scientists can imagine making with olefins, hindering their potential use in drug discovery.

A paper published by UCLA scientists in the journal Science invalidates that idea. These show how to make several types of molecules that violate Bread’s law, called anti-Bread olefins (ABOs), and help chemists find practical ways to create them and use them in reactions .

“The reason people aren’t researching anti-bread olefins is because they think they can’t do it,” said corresponding author Neil, the Kenneth N. Trueblood Distinguished Professor of Chemistry and Biochemistry at UCLA. Garg said.

“We shouldn’t have rules like this. Or if we have rules, they should exist with constant reminders that they are guidelines, not rules. Rules that seem insurmountable can kill creativity.” It will be done.”

Garg’s lab treated molecules called silyl (pseudo)halides with a fluoride source to trigger the elimination reaction that forms ABO. Because ABO is highly unstable, another chemical was included that could “trap” the unstable ABO molecule and produce an isolable product.

The obtained reactions showed that ABO can be generated and captured to give structures of practical value.

“There’s a big push in the pharmaceutical industry to develop chemistries that give us three-dimensional structures like ours, because that can be used to discover new drugs,” Garg said.

“This study shows that, contrary to 100 years of conventional wisdom, chemists can produce and use anti-bread olefins to create value-added products.”

The study’s authors include UCLA graduate students and postdoctoral researchers Luca McDermott, Zachary Walters, Sarah French, Alison Clark, Jiaming Ding, Andrew Kellegan, and Garg. and Ken Hawk, a distinguished research professor at UCLA who is a longtime collaborator and expert in computational chemistry. .

Further information: Luca McDermott et al, A solution to the anti-Bredt olefin synthesis problem, Science (2024). DOI: 10.1126/science.adq3519. www.science.org/doi/10.1126/science.adq3519

Provided by University of California, Los Angeles

Quote: Chemists say it’s time to break 100-year rules and rewrite textbooks (October 31, 2024) https://phys.org/news/2024-10-chemists-broke- Retrieved October 31, 2024 from year-rewrite-textbook.html

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