Chemists map cascade of reactions for producing atmosphere’s ‘detergent’

Criegee intermediates
"Our detailed data proves a much sharper view of the actual dynamics of the troposphere," says theoretical chemist Joel Bowman. In this NASA photo of the space shuttle Endeavor, silhouetted against Earth's atmosphere, the troposphere is the orange layer. The white layer is the stratosphere and the blue is the mesosphere.

Chemists have identified a cascade of reactions for how mysterious molecules known as Criegee intermediates generate hydroxyl radicals – an oxidant that helps remove pollutants from the lower atmosphere.

Nature Chemistry is publishing the findings, a collaboration of Emory University and the University of Pennsylvania.

“We’ve solved another piece of the puzzle in the formation of hydroxyl radicals, by zooming in to see all the steps of the reaction in much finer detail than ever before,” says co-author Joel Bowman, a theoretical chemist at Emory. “This kind of detailed data is important to atmospheric chemists trying to make predictive models for how the atmosphere will respond to climate change.”

The Bowman group collaborated with the lab of experimental chemist Marsha Lester at the University of Pennsylvania.

The theoretical work revealed that a Criegee intermediate first produces highly energized vinyl hydroperoxide, or VHP, then rapidly decomposes to hydroxyl radicals, along with vinoxy byproducts.

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