Interfacial Criegee Chemistry

Criegee intermediates (CIs) in the gas-phase play key roles in the atmospheric HOx cycles and particle formation from organic precursors. The roles at the gas-aerosol interface, however, remain unknown. Recently, interface-specific mass spectrometric study reveals the mechanisms for reactions of Cis with a series of atmospherically relevant compounds including carboxylic acids, alcohols, saccharides and water molecules on the water/acetonitrile mixture surface. CIs generated from ozonolysis of beta-caryophyllene or alpha-humulene on the liquid surface preferentially react with surface-active and acidic species (e.g., cis-pinonic acid) to form larger mass, less volatile products. Surprisingly, levoglucosan and other saccharides efficiently react with Cis at the gas-liquid interface. Large gas-phase acidities of the multiple OH-groups of saccharides underlie their exceptional reactivities toward CIs. Based on these new findings, the roles of interfacial CI reactions in the atmosphere are discussed.