Low-weight Molecular Organic Peroxides, Acids and Carbonyls Production in the Gas-phase OH radical-initiated Reaction of Alpha-pinene at Different Relative Humidity

Abstract:

The photooxidation of biogenic volatile organic compounds (BVOCs) plays an important role in the chemistry of atmosphere. Although alpha-pinene is the most widely observed monoterpene among BVOCs, its photooxidation mechanism is still incompletely understood. In this study, we has investigated the OH radical-initiated reaction of alpha-pinene in the gas phase using a flow tube reactor at different relative humidity, focusing on the low-weight molecular products, including carbonyls, carboxylic acids and organic peroxides. The results show the relationship between these products and water vapor concentrations and indicate that the water vapor may affect the reactions of RO₂ radicals. Interestingly, we find the formation of peroxy carboxylic acids in this reaction for the first time. Our findings provide a useful insight into the role of water vapor in the reaction of alpha-pinene with OH radicals.