Counterintuitive Oxidation of Alcohols at Air–Water Interfaces
Deming Xia, Jingwen Chen, Hong‐Bin Xie, Jie Zhong, Joseph S. Francisco
Abstract
This study shows that the oxidation of alcohols can rapidly occur at air–water interfaces. It was found that methanediols (HOCH 2 OH) orient at air–water interfaces with a H atom of the −CH 2 – group pointing toward the gaseous phase. Counterintuitively, gaseous hydroxyl radicals do not prefer to attack the exposed −CH 2 – group but the −OH group that forms hydrogen bonds with water molecules at the surface via a water-promoted mechanism, leading to the formation of formic acids. Compared with gaseous oxidation, the water-promoted mechanism at the air–water interface significantly lowers free-energy barriers from ∼10.7 to ∼4.3 kcal·mol –1 and therefore accelerates the formation of formic acids. The study unveils a previously overlooked source of environmental organic acids that are bound up with aerosol formation and water acidity.