Eguna: 2025/10/10
Ordua: 11:00
Lekua: Sala Adela Moyúa

"Autoxidation is everywhere in the atmosphere". 
Henrik Grum Kjærgaard. Department of Chemistry, University of Copenhagen, Denmark, hgk@chem.ku.dk

Abstract:

Atmospheric gas-phase autoxidation, the repeated unimolecular reaction followed by uptake of molecular oxygen, has been recognized as a major pathway for the atmospheric oxidation of volatile organic compounds (VOCs). More recently, we have also found autoxidation to be prevalent in compounds that contain a heteroatom: O, N, S, and P. Autoxidation leads to highly oxygenated organic molecules (HOMs) with potentially many functional groups (typically OOH, OH, C=O). The increased number of functional groups and increased size facilitates increased particle uptake and increase hydrogen bond capabilities. The importance of autoxidation is illustrated for some of the most important atmospheric VOCs, like isoprene (C5H8), terpenes (C10H16), dimethyl sulfide [(CH3)2S] and trimethyl amine [(CH3)3N].

The stability of reactive molecules formed in atmospheric reactions depends on their ability to form hydrogen bonds. Unstable hydroperoxides (OOH) are frequently formed in the atmosphere. In cases with rapid autoxidation, formation of molecules with multiple hydroperoxide groups and even a hydrotrioxide group (OOOH) is possible. The surprising stability of these highly reactive molecules is facilitated by multiple hydrogen bonds.