Reactions of Criegee Intermediates with Alcohols at Air–Aqueous Interfaces

Abstract

The fate of Criegee intermediates (CIs) from the gas-phase ozonolysis of unsaturated organic compounds in the troposphere is largely controlled by their reactions with water vapor. We recently found that against all expectations carboxylic acids compete at millimolar concentrations with water for CIs at the air-liquid interface of aqueous organic media. This outcome is consistent with both the low water concentration in the outermost interfacial layers and the enrichment of the competing acids therein. Here we show, via on-line electrospray mass spectrometric detection, that CIs generated in situ in the fast ozonolysis of sesquiterpenes (C15H24) on the surface of water:acetonitrile microjets react with n ≥ 4 linear alcohols CnH2n+1OH to produce high molecular weight Cn+15 ethers in one-step. The OH-group of 1-octanol proved to be ~ 25 times less reactive than that of n-octanoic towards CIs at the same bulk molar concentration, revealing that the reactivity of hydroxylic species both depends on acidities and interfacial affinities. CIs interfacial reactions with surface-active hydroxylic species, by bypassing water, represent shortcuts to molecular complexity in atmospheric aerosols.