Old molecular reaction yields new lesson

BY GEOFF KOCH

Stanford researchers have observed that molecules formed by the reaction of methane and atomic hydrogen scatter in unexpected ways. The results appeared Oct. 14 on the website of the journal Angewandte Chemie.

"This means one of the simplest reactions in chemistry was misunderstood for years," said Richard N. Zare, the Marguerite Blake Wilbur Professor in Natural Science.

This schematic shows that when atomic hydrogen and methane react, the products scatter in unexpected directions. Courtesy Richard Zare

Led by graduate students Jon Camden and Hans Bechtel, the group observed the reaction by using a technique roughly analogous to watching baseball slugger Barry Bonds at the plate. It is nearly impossible to see with the naked eye the moment Bonds' bat strikes the ball, yet most fans at the ballpark have no difficulty picking up the trajectory of his home runs.

Similarly, while chemical reactions happen in the blink of an eye, a sophisticated laser technique developed at Stanford allows researchers to "watch" the aftermath of these reactions in striking detail.

The reaction was thought to be well understood. In fact, hundreds of studies over the last several decades have explored how methane, one of the most common carbon-based molecules on Earth, reacts with hydrogen, the most abundant atom in the universe.

Yet these findings send many -- including the theoretical chemists whose mathematical models had predicted a different scattering pattern -- back to the drawing board.

Zare, the winner of the 2003 Hoagland Prize for teaching excellence, said this research is a reminder of the potential to learn from commonplace phenomena. "This is about a new understanding of something fundamental in nature."