Terpenylic Acid and Related Compounds from the Oxidation of α-Pinene: Implications for New Particle Formation and Growth above Forests

Abstract

SummaryThere are 9 pages in this Supporting Information, including 1 table, 4 figures, 5 schemes, and 10 references. S1. Aerosol samplesThe α-pinene SOA samples used for the time course analysis (Fig. S1) were obtained from an ozonolysis experiment carried out at the IfT in the 9 m 3 Teflon smog chamber (S1). Briefly, α-pinene ozonolysis was performed in the presence of acidic seed particles (0.03 M (NH 4 ) 2 SO 4 /H 2 SO 4 ). No OH scavenger was used in this experiment. The relative humidity and temperature of the chamber were around 50% and 23 ºC. The initial concentrations of α-pinene, ozone, and seed particles were 100 ppb, 60 ppb, and 20,000 cm -3 , respectively. A more detailed description of the experimental procedure is given in (S1). Samples were collected using a condensation-growth and impaction system (C-GIS). Details about the C-GIS sampling system are reported in a previous study (S2). S2. Preparation of standardsTerpenylic acid was prepared from homoterpenyl methyl ketone as reported by Baeyer (S3) (Scheme S1). 5 g of cis-pinonic acid (Aldrich, cis-3-acetyl-2,2-dimethylcyclobutaneacetic acid) was dissolved in 60 g of H 2 SO 4 (50%) at 100 °C and left for 30 min, resulting in a brown mixture with yellow-green fluorescence. Subsequently, 150 mL of water was added to the mixture, the mixture was further saturated with (NH 4 ) 2 SO 4 and the organic phase was extracted with CHCl 3 . The resulting extract was dried over Na 2 SO 4 , the solvent was evaporated to yield homoterpenyl methyl ketone, and the product was re-crystallized from water. In a subsequent step, homoterpenyl methyl ketone was oxidized as reported by Wallach (S4) (Scheme S1). 3 g of homoterpenyl methyl ketone was dissolved in a 0.93 M KOH solution (60 ml), and 300 mL of 0.158 M KMnO 4 solution was added to the solution within 20 min. After filtration of the brown precipitate, the solution was acidified with 10% H 2 SO 4 and repeatedly extracted with diethyl ether. The extract was dried over Na 2 SO 4 and the solvent was evaporated to yield terpenylic acid.The preparation of diaterpenylic acid acetate is given in the supporting information of Iinuma et al. (S5).

High-molecular-weight esters in <i>α</i>-pinene ozonolysis secondary organic aerosol: structural characterization and mechanistic proposal for their formation from highly oxygenated molecules

“…In addition, it can be explained that this labile intermediate can also give rise to the formation of terpenylic acid, a major monomer observed in α-pinene/O 3 SOA (Fig. S3) (Claeys et al, 2009) but here again a complex rearrangement has to be invoked (Scheme S6). In this context, there is evidence that unstable hetero-oligomers present in α-pinene/O 3 SOA produce terpenylic acid upon heating (Lopez-Hilfiker et al, 2015).…”

Organic Constituents on the Surfaces of Aerosol Particles from Southern Finland, Amazonia, and California Studied by Vibrational Sum Frequency Generation

“…Dimerization and oligomerization processes have been reported to be important as well, 45−48 along with the formation of pinic acid and terpenylic acid. 49 Likewise, the oxidation of isoprene, which is the dominant plant emission in tropical forests, has been reported to involve species such as epoxides, which also exhibit lower volatility and higher solubility than isoprene in aerosol and/or cloud droplets. 50,51 The lower vapor pressures of the oxidized compounds 52−55 can lead to their condensation, ultimately contributing, along with aqueous phase pathways, to the production and growth of SOA particles.…”

Role of the reaction of stabilized Criegee intermediates with peroxy radicals in particle formation and growth in air

“…Several pathways leading to oligomer formation have been suggested, including (i) reactions of stabilized Criegee intermediates (SCI) with carboxylic acids and carbonyls, forming a-acyloxy hydroperoxides and secondary ozonides, respectively; 12,15,[18][19][20] (ii) reactions of monomer products from ozonolysis, e.g., aldol condensation, peroxyhemiacetal formation, gem-diol formation, esterification, acetal and hemiacetal formation; 13,16,18,[21][22][23][24][25][26] and (iii) formation of non-covalently bound dimer clusters of carboxylic acids. 21,[26][27][28] Pathway (i) is thought to take place in the gas phase, and pathway (ii) is suggested to occur mainly on the surface or within the bulk of SOA particles, whereas pathway (iii) may occur in both phases. Quite recently, gas phase formation of esters 17 and highly oxidized products (termed extremely low-volatility organic compounds, ELVOCs) [29][30][31][32] have been suggested in the a-pinene/O 3 system.…”