A Century-Old Chemistry Rule Has Been Shown To Be Wrong....The discovery could lead to making useful organic molecules that have been treated as impossible.

IFL Science ^ | November 01, 2024 | Stephen Luntz

[Red Badger]

A way to link carbon rings thought impossible for a century has now been done, and could have medical applications.

For exactly 100 years, chemists have considered double bonds impossible – or nearly so – in organic chemistry under specific circumstances. Known as Bredt’s rule, this axiom was based not on theory, but decades of previous observations of molecules where such bonds were lacking. Confidence was high enough that it has widely been published in textbooks. New research shows it’s not true, and will encourage chemists to look for molecules they previously thought couldn’t exist.

Carbon is such an immensely versatile element that the vast majority of molecules we know of contain it. Since we ourselves are composed primarily of molecules built around a carbon structure, the study of what is and isn’t possible with carbon, i.e. organic chemistry, is particularly crucial for us.

Key to carbon’s molecule-making flexibility is that it forms four bonds, which can involve single, double, or triple bonds with other carbon molecules. However, Julius Bredt claimed to find a limitation on that capacity. Where a molecule contains two rings of carbon atoms, joined together by a bridge, Bredt claimed the bridgehead cannot involve a double bond. Now UCLA chemists have shown that it can.

Although Bredt reached this conclusion based on noticing an absence of such double bonds in relevant molecules, an explanation subsequently arose that double bonds in these circumstances would twist the molecule out of a plane. Since then, the rule has been modified twice. Double bonds between larger ring systems are now accepted as existing. Moreover, other chemists have claimed to make such molecules with smaller rings, but found them unstable, so the rule is now taken as precluding lasting molecules with smaller ring systems. In this form the rule is recognized by the International Union of Pure and Applied Chemistry.

However, Professor Neil Garg heads a team that has found molecules that violate the rule. These “anti-Bredt olefins” (ABOs) could be just the tip of the iceberg, since several kinds have been identified already.

The ABOs were made by applying fluoride to molecules whose names sound like they come from a sketch mocking chemists: silyl (pseudo)halides. The ABOs produced were initially unstable, showing the rule was not entirely wrong, but the team then used a variety of agents to trap them enough to analyze and potentially use. Maybe the pseudohalides are not so silyl after all.

Among scientists, as with other people, there are always those who most want to do the thing they are told is impossible. However, far more have accepted Bredt’s rule, at least in modified form, and not looked back.

“People aren’t exploring anti-Bredt olefins because they think they can’t,” Garg said in a statement. They haven’t been ignoring ABOs because they thought they would be useless, however.

“There’s a big push in the pharmaceutical industry to develop chemical reactions that give three-dimensional structures like ours because they can be used to discover new medicines,” Garg said. “What this study shows is that contrary to one hundred years of conventional wisdom, chemists can make and use anti-Bredt olefins to make value-added products.”

Discoveries like this raise questions about how often textbooks are wrong in other ways. Garg sees the problem as treating observational rules as if they were fundamental laws. “We shouldn’t have rules like this – or if we have them, they should only exist with the constant reminder that they’re guidelines, not rules. It destroys creativity when we have rules that supposedly can’t be overcome.”

The study is published in Science.

http://dx.doi.org/10.1126/science.adq3519

[AFreeBird]

But, but, but; Carbon is bad. Every says so, I even heard it on the TeeVee. Oh the Hugh Manatee.

[NorthMountain]

Fraud (noun):
(1) deceit, trickery, sharp practice, or breach of confidence, perpetrated for profit or to gain some unfair or dishonest advantage.

(2) a particular instance of such deceit or trickery:
mail fraud; election frauds.

(3)any deception, trickery, or humbug:
That diet book is a fraud and a waste of time.

Synonyms: hoax, wile

(4) a person who makes deceitful pretenses; sham; poseur.

---

I’m getting the sense, here, that I’ve gored YOUR ox; slain YOUR sacred cow ... and you’re butthurt over it.

“Creation Science” is possibly the most egregious example of cherry-picking data and assuming the conclusion that I have ever seen. It’s worse than Flat-Earth.

[wbarmy]

No, just kind of sad that you have made your decision and probably have no real examples to back it up. I used to be a full bore evolutionist but started realizing that evolution is more than just a belief system and worldview, it is a money maker for a whole lot of so called scientists.

Additionally, all three of the explanations you provided for fraud, is about making money. The mail scam is to make money, the diet book is to make money. The synonym doesn’t count. So, this is still about funding. I always follow the money in these instances and it is always about the money.

[coloradan]

Thanks for posting the structures!

[bert]

Those who have no science and no chance of acquiring some, like to whine when there is change.

By requiring certainty, they insist that change in the perceived certainty of settled science proves their ignorance to be correct

[alloysteel]

Science, any REAL science, is never settled. Because human beings have only fragmentary knowledge of the Universe, there are exceptions and surprises behind every assumption and conclusion arrived at by the sometimes blind fumbling of trying to apply rules where chaos exists.

[BiteYourSelf]

Weird science.😁

[Zuben Elgenubi]

Good heavens, Miss Sakamoto, you’re beautiful!

Priceless