Alkoxy radical bond scissions explain the anomalously low secondary organic aerosol and organonitrate yields from α-pinene + NO

However, knowledge of the mechanisms of their formation is incomplete and differences in yields between similar monoterpenes are poorly understood. In particular, yields of SOA and organonitrates from alpha-pinene + NO3 are low, while those from Delta(3)-carene + NO3 are high.

Using computational methods, we suggest that bond scission of the nitrooxy alkoxy radicals from Delta(3)-carene lead to the formation of reactive keto-nitrooxy-alkyl radicals, which retain the nitrooxy moiety and can undergo further reactions to form SOA. By contrast, bond scissions of the nitrooxy alkoxy radicals from alpha-pinene lead almost exclusively to the formation of the relatively unreactive and volatile product pinonaldehyde (C10H16O2), thereby limiting organonitrate and SOA formation.