An elusive molecule has finally been discovered

An age-old chemical mystery finally solved, the discovery of OCCO may lead to possible applications ranging from innovative industrial processes to environmental chemistry.

[Translation by Dr. Nachmani Moshe]

Scientists from the University of Arizona have uncovered a mysterious molecule, which, although its structure on paper is very simple, has still caused chemists to debate the structure, or even the very possibility of its existence, for more than a hundred years; And like many of the most important discoveries in science, this discovery was born from a vial that had been forgotten for a long time in a freezer, in this case in the laboratory of Andrei Sanov, a professor in the Department of Chemistry and Biochemistry at the University of Arizona.

The team of researchers reported the first ever proven observation and spectroscopic characterization of the substance ethylenedione, or "OCCO", which represents two carbon monoxide molecules chemically bound together. This molecule attracts a lot of interest for many reasons: from its supposed role as an extremely fast intermediate in many chemical reactions to its supposed properties as a miracle drug. The researchers prepared the molecule of interest from its corresponding negative ion, and used a measurement method called photoelectron imaging spectroscopy to analyze the final product. In this method, laser pulses are used to remove electrons from molecules, with the aim of creating positively charged ions. The findings proved the existence of the stealth species and also revealed their important fundamental properties, with applications not only for the understanding of molecular species known as radicals, but also for applications in the fields of industrial processes and use in environmental chemistry and climate modeling.

Chemists have been studying this molecule, again and again, since 1913, when its very existence was first proposed. In the 40s of the last century, it was particularly controversial in the days of the molecule, it was claimed to be the active form of the substance Glyoxylide, and was proposed as a medicine against a long list of pains, from exhaustion to cancer. These claims were found to be false after an inspection by the US Food and Drug Administration (FDA) which proved that the tested substance is nothing but water; And despite this, to this day there are stories about the myth of this substance as a lost miracle cure for cancer.

According to the lead researcher, one of the incentives for proving the existence of the molecule ethylenedione is the basic elegant puzzle it presents: most students with a basic chemical education can easily sketch the structural formula of the molecule: O=C=C=O. Over the years, the expected existence of the molecule was also supported by the prediction results of advanced theories. And at the same time, all previous studies failed to provide solid experimental proof that the molecule does exist - and therein lies the enigma. "We are not talking here about some complex compound," says the lead researcher. "This is a small molecule with only four atoms and a fairly clear structure. Doesn't it make sense that modern science could solve this issue"?

The key to the mystery lies in the unstable nature of the molecule, which tends to break down into two molecules of carbon monoxide (CO) after only half a nanosecond. The molecule itself is referred to by chemists as a di-radical. Radicals and di-radicals play a particularly important role in controlling the mechanisms and products of chemical reactions, reactions that occur in all areas of life, industry, technology and the environment. "Radicals and di-radicals are everywhere around us," says the researcher. "They can be imagined as molecules with unpaired electrons that function as "unemployed" substances looking for interest, meaning - they are eager to react with other particles. A radical is a molecule with one such unpaired electron, and a di-radical is a molecule with two such electrons."

The researcher explains: "We started the research in light of our interest in di-radical systems and as part of these experiments, we decided to purchase the substance glyoxal, a profitable substance in the industry that has not been thoroughly examined as a possible molecule for synthesis applications due to its high water content, which means that its treatment will become particularly challenging", explains the researcher. "We saw that the water content in it is close to 60%, so I said to myself - well, we will return to this material in the future." During a conversation with a professional colleague, the researchers became aware of another molecule that serves as a "molecular sieve" that removes the high water content of glyoxal. "Once we got the molecule in a gaseous state, we could examine it in our mass spectrometer and we were able to get a clear and sharp signal of it. We tried to find a name for the new molecule, and the Wikipedia site provided us with the name ethylenedione. Only then did we notice that we had found something new." In the next step, the researchers applied laser pulses for extremely short periods of time on the material and defined with great precision the energies obtained in the new molecule. "In our spectroscopic system, we can turn on the laser exactly when an expected OCCO anion passes through a defined point."

In the next step, after sifting through the molecules they needed, the researchers were able to remove excess electrons from the stable ion of the substance ethylenedione. In the next step, they obtained photoelectron images of the quantum states of the substance at the very beginning of its formation, when its lifetime was only half a nanosecond. In light of the fact that the substance glyoxal, the starting material, has an important role in atmospheric chemistry, the researchers speculate that the OCCO formation may also play an important role, a finding that could improve future climate models. "In light of the fact that glyoxal, the starting material, is known to be a pollutant and a byproduct of burning processes, whether man-made or not, and that the OCCO form can be produced in a laboratory using our method, it is possible that it was also formed in these burning processes, and may be a substance that we have not yet given our scientific opinion on Its role in the atmosphere, which interferes with obtaining accurate climate models." "One of the most important findings of our research is the end of the age-old controversy surrounding the question of the existence of this molecule," says the lead researcher. "The theoretical prediction was correct - the di-radical OCCO does exist. Finally, we managed to find and characterize it."

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