Decomposition pathways of isoprene-derived hydrotrioxides and their clustering abilities in the atmosphere†

Abstract

In atmospheric gas-phase chemistry, hydrotrioxides (ROOOH) are formed as intermediates in the reactions of peroxyl radicals (RO₂) with OH radicals, and their stabilization has been confirmed experimentally by direct observation. In this study, we systematically investigated the probable decomposition pathways of isoprene-derived ROOOHs in the atmosphere. The kinetic analysis confirmed that the fast fragmentation of hydrotrioxides into their respective alkoxy radicals and hydroperoxyl radicals dominates over the other decomposition mechanisms. We also explored the decomposition of ROOOH proceeding via³(RO⋯HO₂) product complexes, through which an intermolecular hydrogen transfer results in the formation of alcohol and molecular oxygen with a relatively low energy barrier. Furthermore, we studied the clustering abilities of hydrotrioxides with various types of atmospheric vapors, particularly acids and amines. The results indicate that the binding strength of these hydrotrioxides with other vapors is too low to drive clustering processes at ambient atmospheric concentrations, however, hydrotrioxides interact more strongly with bases and acid–base clusters than alcohols or hydroperoxides. These findings provide insight into the atmospheric stability and reactivity of hydrotrioxides, with implications for understanding their role in processes such as secondary organic aerosol formation.