Experimental and Theoretical Studies of Trans-2-Pentenal Atmospheric Ozonolysis

We investigated the kinetics, mechanism and secondary organic aerosols formation of the ozonolysis of trans-2-pentenal (T2P) using four different reactors with Fourier Transform InfraRed (FTIR) spectroscopy and Gas Chromatography (GC) techniques at T = 298 +/- 2 K and 760 Torr in dry conditions. The rate coefficients and branching ratios were also evaluated using the canonical variational transition (CVT) state theory coupled with small curvature tunneling (CVT/SCT) in the range 278-350 K. The experimental rate coefficient at 298 K was (1.46 +/- 0.17) x 10(-18) cm(3) molecule(-1) s(-1), in good agreement with the theoretical rate. The two primary carbonyls formation yields, glyoxal and propanal, were 57 +/- 10% and 42 +/- 12%, respectively, with OH scavenger compared to 38 +/- 8% for glyoxal and 26 +/- 5% for propanal without OH scavenger. Acetaldehyde and 2-hydroxypropanal were also identified and quantified with yields of 9 +/- 3% and 5 +/- 2%, respectively, in the presence of OH scavenger. For the OH production, an upper limit of 24% was estimated using mesitylene as OH tracer. Combining experimental and theoretical findings enabled the establishment of a chemical mechanism. Finally, the SOA formation was observed with mass yields of about 1.5%. This work provides additional information on the effect of the aldehyde functional group on the fragmentation of the primary ozonide.