Interfacial vs Bulk Ozonolysis of Nerolidol

摘要

Ozone readily reacts with olefins with the formation of more reactive Criegee intermediates (CIs). The transient CIs impact HOx cycles, and they play a role in new particle formation in the troposphere. Oxidation by O-3 occurs both in the gas-phase, in the liquid phase, and at air-water and air-aerosol interfaces. In light of the importance of O-3 in environmental and engineered chemical transformations, we have investigated the ozonolysis mechanisms of a triolefin C-15-alcohol, nerolidol (Nero, a biogenic sesquiterpene), at the air-water interface in the presence of acetonitrile. Surface-sensitive pneumatic ionization mass spectrometric detection of alpha-hydroxy-hydroperoxides and functionalized carboxylates, generated by the hydration and isomerization of CIs, respectively, enables us to evaluate the relative reactivity of each C=C toward O-3. In addition, we compare bulk-phase ozonolysis chemistry to similar reactions taking place at the air-water interface. Our experimental results show that O-3 reacts primarily with the (CH3)(2)C=CH- and -(CH3)C=CH- moieties (similar to 98%), while the O-3 attack on the terminal -HC=CH2 site (similar to 2%) is a minor pathway during both interfacial and bulk ozonolysis. The presence of functionalized-carboxylates on interfaces but not in bulk-phase reactions with O-3 indicates that the isomerization of the CIs is not hindered at the air-water interface due to the lower availability of water.