New kind of chemical bond Found

It’s taken years to nail down, but scientists in Canada have at last found a new chemical bond, which they’re named a ‘vibrational bond’.

This vibrational bond appears to violate the law of chemistry that says if you rise the temperature, the rate of reaction will increase. Back in 1989, a group from the University of British Columbia studied the reactions of numerous elements to muonium (Mu) - a peculiar, hydrogen isotope made up of an antimuon and an electron. They used chlorine and fluorine with muonium, and as they raised the heat, the reaction time raced up, but when they used bromine (br), a brownish-red toxic and acid liquid, the reaction time raced up as the temperature reduced. The scientists, Amy Nordrum writes for Scientific American, "were flummoxed”. 

Possibly, supposed one of the team, chemist Donald Flemming, when the bromine and muonium made interaction, they made a transitional structure made up of a lightweight atom bordered by two heavier atoms. And the structure was combined not by van der Waal’s forces - as would typically be estimated - but by some kind of momentary ‘vibrational’ bond that had been suggested decades ago.

Nordrum clarifies:

"In this situation, the lightweight muonium atom would move fast between two heavy bromine atoms, 'like a Ping Pong ball rebounding among two bowling balls,' Fleming says. The oscillating atom would momentarily hold the two bromine atoms together and decrease the overall energy, and consequently speed, of the reaction.”

But back then, the group didn’t have the technology required to truly see this reaction take place, since it lasts for just a few milliseconds. But now they do, and the group took their study to the nuclear accelerator at Rutherford Appleton Laboratory in England. 

With the support of theoretical chemists from the Free University of Berlin and Saitama University in Japan, Flemming’s group observed as the light muonium and heavy bromine made a momentary bond. “The lightest isotopomer, BrMuBr, with Mu the muonium atom, alone displays vibrational bonding in agreement with its probable observation in a new experiment on the Mu + Br2 reaction,” the group reports in the journal Angewandte Chemie International Edition. "Accordingly, BrMuBr is stabilised at the saddle point of the potential energy surface due to a net decrease in vibrational zero point energy that overcompensates the increase in potential energy.” 

In other words, the vibration in the bond lessened the total energy of the BrMuBr structure, which means that even when the temperature was amplified, there was not sufficient energy to perceive an rise in the reaction time. 

While the group only observed the vibrational bond happening in a bromine and muonium reaction, they are suspicious that it can also be establish in interactions between lightweight and heavy atoms, where van der Waal’s forces are supposed to be at play.

"The work confirms that vibrational bonds - fleeting though they may be - should be added to the list of known chemical bonds,” says Nordrum at Scientific American.

Sorry, upcoming high school chemistry schoolchildren, here is another thing you'll possibly have to study.

Source: Scientific American

Chemical Bonding


Post A Comment: