Thermodynamics and kinetics of the hydrolysis of atmospherically relevant organonitrates and organosulfates

摘要

The presence of alcohol, organonitrate, and organosulfate species related tothe gaseous precursor isoprene in ambient secondary organic aerosol (SOA)has stimulated investigations of the nature of SOA-phase chemicalprocessing. Recent work has suggested that certain isoprene-derivedorganonitrates are able to efficiently convert to organosulfates andalcohols on ambient SOA. In order to better understand the structureactivity relationships previously observed for the isoprene-derivedorganonitrates and organosulfates, the hydrolysis reactions of a number ofmonofunctional and difunctional organonitrates and organosulfates withvarying carbon substitution properties were investigated. Nuclear magneticresonance techniques were used to study the bulk phase aqueous reactions ofthese organonitrates and organosulfates in order to determine hydrolysisreaction rate and, in some cases, thermodynamics information. Electronicstructure calculations were also carried out to determine the enthalpy ofhydrolysis for these species, and for the previously studiedisoprene-derived species. The results suggest that while organonitrates andorganosulfates are thermodynamically unstable with respect to thecorresponding alcohols at standard state, only the tertiary organonitrates(and perhaps some tertiary organosulfates) are able to efficiently hydrolyzeon SOA timescales and acidities.