Structural Analysis of Oligomeric Molecules Formed from the Reaction Products of Oleic Acid Ozonolysis

Abstract

The products arising from the ozonolysis of oleic acid (cis-9-octadecenoic acid) in solution have been studied using negative ion mode electrospray ionization ion trap mass spectrometry. Oleic acid is an important component of atmospheric organic aerosol and is a key model species in predicting aerosol physical and chemical characteristics. The four predicted reaction products, 1-nonanal, nonanoic acid, 9-oxononanoic acid, and azelaic acid, were all observed in roughly equal yields. In addition to these products a large number of higher molecular weight compounds were detected with m/z ratios of up to 1000 Daltons. Tandem mass spectrometry of these larger ions revealed thatthey represented a complex mixture of linear alpha-acyloxyalkyl hydroperoxides, secondary ozonides, and cyclic diperoxides, formed by reactions between ozonolysis products and Criegee intermediates. These comprise the first directly elucidated structures of large oligomeric species from oleic acid ozonolysis. The degree of oligomerization and hence molecular weight distribution was observed to increase with reaction time in solution.

The ozonolysis of primary aliphatic amines in fine particles

“…3.5 A mechanistic account for the formation of the observed products in the ozonized mixed particles A detailed account of the heterogeneous ozonolysis of OL has recently been published (Zahardis and Petrucci, 2007) and many mechanistic depictions are available in the literature (Ziemann, 2005;Zahardis et al, 2005;Hung et al, 2005;Reynolds et al, 2006;Katrib et al, 2004). The three main steps of ozonolysis of oleic acid are in accord with established solution phase chemistry (Bailey, 1978): …”

“…As of late, a great deal of effort has gone into understanding the secondary chemistry resulting from the ozonolysis of unsaturated fatty acids (Zahardis et al, 2005;Ziemann, 2005;Hearn et al, 2005;Reynolds et al, 2006;Hung et al, 2005;Gross et al, 2006) and OL has emerged as a model compound for describing the heterogeneous ozonolysis of particulate rich in fatty acid content (for example, see review by Zahardis and Petrucci, 2007). The products of this secondary chemistry generally stem from the high reactivity of stabilized Criegee intermediates (SCI) and include high molecular weight, peroxidic oligomers (Reynolds et al, 2006;Hung and Ariya, 2007;Zahardis et al, 2006a;Katrib et al, 2005;Hung et al, 2005;Gross et al, 2006;Hearn et al, 2005;Ziemann, 2005). These types of products may have a role in the experimentally observed increase in hygroscopicity and CCN activation of fine organic particles with ozonation (Broekhuizen et al, 2004;Shilling et al, 2007;King et al, 2004;Hung and Ariya, 2007).…”

“…OOCH(CH 2 ) 7 CO 2 H and OOCH(CH 2 ) 7 CH3) (Ziemann, 2005;Zahardis et al, 2005;Hearn and Smith, 2004;Hung et al, 2005) or, conversely, form as decomposition products of the secondary ozonides and other peroxides as higher generation reaction products (Martin, 2006b, a). Recent mass spectral evidence (Reynolds et al, 2006) suggests that fragmentation occurring in the ionization process of high molecular weight peroxides may also contribute to the evolution of ions corresponding to these acids. A more extensive discussion of the formation of these acids as well and other mechanistic features of this reaction system are beyond the scope of this report and have been covered elsewhere (Zahardis and Petrucci, 2007).…”

The relative importance of competing pathways for the formation of high-molecular-weight peroxides in the ozonolysis of organic aerosol particles

“…Ozonolysis reaction kinetics have been studied, including the gas-phase loss rate of ozone, the condensed-phase loss rate of the organic compound, and the effects of chemical mixtures, particle morphology, and physical state on those loss rates (Moise and Rudich, 2002;Morris et al, 2002;Smith et al, 2003;Katrib et al, 2005a, b;Knopf et al, 2005;Ziemann, 2005). Product identification and yields resulting from ozonolysis, as well as the associated reaction mechanisms, have been investigated (Katrib et al, 2004;Hearn and Smith, 2004;Zahardis et al, 2006a, b;Hung et al, 2005;Ziemann, 2005;Reynolds et al, 2006). Ozone-induced changes in particle properties, including hygroscopicity (Asad et al, 2004), CCN activity (Broekhuizen et al, 2004), and density (Katrib et al, 2005b), have been quantified.…”

“…Several of these studies suggest the occurrence of ozoneinduced oligomerization inside atmospheric aerosol particles as the ultimate fate of a portion of the stabilized Criegee intermediates (SCI's) (Hung et al, 2005;Zahardis et al, 2005Zahardis et al, , 2006aZiemann, 2005;Reynolds et al, 2006). SCI's are primary products of the ozonolysis of unsaturated organic molecules.…”