Effect of Relative Humidity on the Chemical Composition of Secondary Organic Aerosol Formed from Reactions of 1-Tetradecene and O₃

The chemical composition of secondary organic aerosol formed in an environmental chamber from ozonolysis of 1-tetradecene in humid and dry air was determined using a thermal desorption particle beam mass spectrometer (TDPBMS). The major products are α-hydroxytridecyl hydroperoxide and bis(α-hydroxytridecyl) peroxide in humid air and symmetric C26 and asymmetric C14 secondary ozonides in dry air. The hydroperoxide is formed by reaction of stabilized Criegee biradicals with water vapor, and the peroxide (a peroxyhemiacetal) is formed by subsequent reaction of the hydroperoxide with tridecanal. The secondary ozonides are formed by reactions of stabilized Criegee biradicals with tridecanal and formaldehyde. Tridecanoic acid was also observed in both experiments. These compounds have very low vapor pressures and are stable on the 3-h time scale of the environmental chamber experiments. When collected aerosol was analyzed by gas chromatography, the hydroperoxides, peroxides, and secondary ozonides thermally decomposed to more volatile compounds, including tridecanal, tridecanoic acid, and a few unidentified products.