Journal Article

Selective deuteration as a tool for resolving autoxidation mechanisms in α-pinene ozonolysis

Geiger, Franz M, Zhang, Yanjun, Varelas, Jonathan G, Ehn, Mikael, Kurtén, Theo, Thomson, Regan J, Riva, Matthieu, Luo, Jingyi, Cai, Runlong, Rissanen, Matti, Peräkylä, Otso, Meder, Melissa

2023

Overview

Highly oxygenated organic molecules (HOMs) from α-pinene ozonolysis have been shown to be significant contributors to secondary organic aerosol (SOA), yet our mechanistic understanding of how the peroxy-radical-driven autoxidation leads to their formation in this system is still limited. The involved isomerisation reactions such as H-atom abstractions followed by O.sub.2 additions can take place on sub-second timescales in short-lived intermediates, making the process challenging to study. Similarly, while the end-products and sometimes radical intermediates can be observed using mass spectrometry, their structures remain elusive. Therefore, we propose a method utilising selective deuterations for unveiling the mechanisms of autoxidation, where the HOM products can be used to infer which C atoms have taken part in the isomerisation reactions. This relies on the fact that if a C-D bond is broken due to an abstraction by a peroxy group forming a -OOD hydroperoxide, the D atom will become labile and able to be exchanged with a hydrogen atom in water vapour (H.sub.2 O), effectively leading to loss of the D atom from the molecule.

• Publisher: Copernicus GmbH
• Subject: Hydrogen / Isomerization / Mass spectrometry