Structures and reactivity of peroxy radicals and dimeric products revealed by online tandem mass spectrometry

Abstract

Organic peroxy radicals (RO2) play a pivotal role in the degradation of hydrocarbons. Theautoxidation of atmospheric RO2 radicals produces highly oxygenated organic molecules(HOMs), including low-volatility ROOR dimers formed by bimolecular RO2 + RO2 reactions.HOMs can initiate and greatly contribute to the formation and growth of atmospheric particles.As a result, HOMs have far-reaching health and climate implications. Nevertheless, thestructures and formation mechanism of RO2 radicals and HOMs remain elusive. Here, wepresent the in-situ characterization of RO2 and dimer structure in the gas-phase, using onlinetandem mass spectrometry analyses. In this study, we constrain the structures and formationpathway of several HOM-RO2 radicals and dimers produced from monoterpene ozonolysis, aprominent atmospheric oxidation process. In addition to providing insights into atmosphericHOM chemistry, this study debuts online tandem MS analyses as a unique approach for thechemical characterization of reactive compounds, e.g., organic radicals.