Researchers Discover New Insights into Carbene Formation

Researchers Discover New Insights into Carbene Formation
by Clarence Oxford
Los Angeles CA (SPX) May 20, 2024

A team led by University of Maryland chemists has found a new method to create carbenes, highly reactive molecules essential for many chemical reactions, including those that produce carbohydrates. Carbenes are important precursors to the building blocks of life on Earth and potentially in space.

The researchers created hydroxymethylene (HCOH), a carbene, by breaking down methanol (CH3OH) with ultraviolet radiation. The results were published on May 14, 2024, in the Journal of the American Chemical Society.

"It's surprising to see this carbene come from such a commonplace molecule like methanol-we have squirt bottles of it in labs everywhere," said Leah Dodson, an assistant professor of chemistry and biochemistry at UMD and senior author of the paper. "193-nanometer wavelength UV lasers are also fairly standard. This means that carbenes could be naturally forming in places like space, where there is a lot of methanol and ultraviolet radiation. And further reactions of carbenes formed in space through this process could lead to biomolecules that make up life."

The findings provide clues about the mechanisms behind carbene formation and reaction on Earth, leading to a better understanding of their potential to create sugars necessary for life.

"There's established research that suggests that HCOH can react to form simple sugars, including some that have previously been detected in space," said Emily Hockey, the study's lead author. "We think it's possible that this carbene, since it comes from a molecule that's so ubiquitous in space and can be detected anywhere, is the missing piece bridging gaps in our knowledge of how methanol and simple sugars can lead to bigger, more advanced biomolecules."

Carbene molecules usually have very short lifetimes due to their reactivity, making them difficult to study. However, the UMD team's method allowed them to observe the formation and decay of carbenes over millisecond timescales. They discovered that HCOH reacted relatively slowly with oxygen at room temperature.

"When we looked at HCOH's reactivity in our room temperature system, we saw that it decayed within 15 milliseconds," Hockey explained. "What's interesting is that because carbenes are thought to be a super reactive species, it's reasonable to assume that this carbene would react so quickly to something like oxygen that it's impossible to catch. But that's not what happened. Although the carbene was decaying faster and faster when exposed to oxygen, it was slow enough that we were still able to observe that decay."

The researchers believe their method will help astronomers and astrochemists gain new insights into the origins of life and how it may have evolved differently in space. They plan to investigate further by examining methanol's breakdown and the products it yields when exposed to UV light.

"We know that carbenes like HCOH are formed during our process, but we'd like to dig deeper into what percentage of it ends up as formaldehyde, methylene or other hydrocarbon radicals, for example," Hockey explained. "We originally thought all the products would be methoxy radicals but our experiments show that the process and the resulting products are more complicated than our original assumptions."

Understanding the products created by breaking down methanol with UV radiation would provide a more accurate outlook on astrophysical objects and their evolution over billions of years.

"If the existing data on what is produced from methanol photodissociation are wrong, then the models being propagated will be incorrect as well-and our understanding of how life evolved from these molecules could also be compromised," Dodson said. "Our follow-up work will hopefully lay the groundwork for those types of simulations."

Research Report:Direct Observation of Gas-Phase Hydroxymethylene: Photoionization and Kinetics Resulting from Methanol Photodissociation