Theoretical chemists at Emory University have solved an important mystery about the rates of chemical reactions and the so-called Polanyi rules.
The findings, published in the journal Science, reveal why a reaction involving methane does not conform to the known rules, a problem that has baffled physical chemists in recent years.
"We showed that a pre-reactive, long-range force can align the reaction of a chorine atom with methane, or natural gas, in a way that actually inhibits the reaction," says Joel Bowman, a professor of theoretical chemistry at Emory and the Cherry L. Emerson Center for Computational Chemistry. "We believe that the theoretical work that we did has extended and modified the Polanyi rules."
Bowman published the results with Gabor Czako, a post-doctoral fellow in theoretical chemistry who performed most of the complex computational and mathematical analyses that uncovered the results.
Long-range, their findings could play a role in the development of cleaner, more efficient fuels.
Understanding the dynamics of chemical reactions is key to driving reactions efficiently, whether in a laboratory experiment or in an industrial application. In 1986, John Polanyi shared the Nobel Prize in chemistry, in part by providing general rules for how different forms of energy affect the rates of reactions.
"The Polanyi rules tell you the best way to deposit energy in a simple molecule to make a chemical reaction occur," Bowman says. "It's a bit like knowing in advance how to invest $1,000 to maximize the return on investment."
Polanyi developed the framework based on studies of simple reactions of chlorine and fluorine atoms with hydrogen gas. As technology has advanced in recent years, some chemists began testing the Polanyi rules for more complicated reactions, and the rules appeared to break down. Most notably, sophisticated molecular beam experiments by Kopin Liu at the Insti
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