Alcohol and Quantum Mechanics: How Chemical Reactions Occur in Frigid Space
Alcohol, it turns out, is quite plentiful in space, and chemists think they might finally know why.
In the vast expanse of the cosmos, temperatures are so low that chemical reactions aren't, according to classical rules of chemistry, able to occur - there simply isn't enough energy. However, occur they do, as seen in the 288 billion-mile cloud of gaseous methanol, an alcohol present in antifreeze and some moonshine.
As way of explanation, scientists previously suggested that dust grains could lend a hand in bringing chemical reactions about by acting as a staging post where the ingredients of complex molecules could cling to.
Last year, however, a highly reactive molecule called the 'methoxy radical' was detected in space, the formation of which could not be explained using this theory.
Laboratory experiments showed that when an icy mixture containing methanol was blasted with radiation, which would likely occur in space, methoxy radicals weren't released in the emitted gases. The findings suggested that, rather than any process taking place on the surface of dust grains, methanol gas was involved in the production of the methoxy radicals found in space.
This, however, brought scientists back to the same problem of the inability of gases to react under extremely cold conditions.
"The answer lies in quantum mechanics," says Professor Dwayne Heard, Head of the School of Chemistry at the University of Leeds, who led the research.
In classical chemistry, he explained, reactions get slower as temperatures drop because there is less energy to overcome the "reaction barrier." Quantum mechanics, on the other hand, states that instead of going over this barrier, "it is possible to cheat and dig through" in a process called "quantum tunneling."
The researchers suggest that an "intermediary product" is formed during the first state of this reaction that only survives long enough for quantum tunneling to occur at extremely low temperatures.
They were able to recreate the cold environment of space in a laboratory and observe a reaction of the alcohol methanol and an oxidizing chemical called the 'hydroxyl radical' at -210 degrees Celsius. To do this, however, the researchers had to create a new experimental setup.
"The problem is that the gases condense as soon as they hit a cold surface," said Robin Shannon from the University of Leeds, who performed the experiments. "So we took inspiration from the boosters used for the Apollo Saturn V rockets to create collimated jets of gas that could react without ever touching a surface."
As a result, they found that not only do these gases react to create methoxy radicals at such low temperatures, but that they do so 50 times faster than at room temperature.
Going forward, the researchers are investigating the reactions of other alcohols at very cold temperatures.
"If our results continue to show a similar increase in the reaction rate at very cold temperatures, then scientists have been severely underestimating the rates of formation and destruction of complex molecules, such as alcohols, in space," Heard concluded.