Structures and reactivity of peroxy radicals and dimeric products revealed by online tandem mass spectrometry
Sophie Tomaz, Dongyu Wang, Nicolás Zabalegui, Dandan Li, Houssni Lamkaddam, Franziska Bachmeier, Alexander L. Vogel, Marı́a Eugenia Monge, S. Perrier, Urs Baltensperger, C. George, Matti Rissanen, Mikael Ehn, Imad El Haddad, Matthieu Riva
Abstract
Abstract Organic peroxy radicals (RO 2 ) play a pivotal role in the degradation of hydrocarbons. The autoxidation of atmospheric RO 2 radicals produces highly oxygenated organic molecules (HOMs), including low-volatility ROOR dimers formed by bimolecular RO 2 + RO 2 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, the structures and formation mechanism of RO 2 radicals and HOMs remain elusive. Here, we present the in-situ characterization of RO 2 and dimer structure in the gas-phase, using online tandem mass spectrometry analyses. In this study, we constrain the structures and formation pathway of several HOM-RO 2 radicals and dimers produced from monoterpene ozonolysis, a prominent atmospheric oxidation process. In addition to providing insights into atmospheric HOM chemistry, this study debuts online tandem MS analyses as a unique approach for the chemical characterization of reactive compounds, e.g., organic radicals.