An experimental study of the gas-phase reaction between Cl atoms and trans-2-pentenal: Kinetics, products and SOA formation

Abstract

The gas-phase reaction of trans-2-pentenal (T2P) with Cl atoms was studied at atmospheric pressure and room temperature. A rate coefficient of (2.56±0.83)×10 -10 cm 3 molecule -1 s -1 was obtained using the relative rate method and isoprene, cyclohexane and ethanol as reference compounds. The kinetic study was carried out using a 300-L Teflon bag simulation chamber (IMT Lille Douai-France) and a 16-L Pyrex cell (UCLM-Ciudad Real-Spain), both coupled to the Fourier transform infrared (FTIR) technique. Gas-phase products and secondary organic aerosol (SOA) formation were studied at UCLM using a 16-L Pyrex cell and a 264-L quartz simulation chamber coupled to the FTIR and gas-chromatography-mass spectrometry (GC-MS) techniques. HCl, CO, and propanal were identified as products formed from the studied reaction and quantified by FTIR, being the molar yield of the latter (5.2±0.2)%. Formic acid was identified as a secondary product and was quantified by FTIR with a yield of (6.2±0.4)%.In addition, 2-chlorobutanal and 2-pentenoic acid were identified, but not quantified, by GC-MS as products. The SOA formation was investigated using a fast mobility particle sizer spectrometer. The observed SOA yields reached maximum values of around 7% at high particle mass concentrations. This work provides the first study of the formation of gaseous and particulate products for the reaction of Cl with T2P. A reaction mechanism is suggested to explain the formation of the observed gaseous products. The results are discussed in terms of the structure-reactivity relationship, and the atmospheric implications derived from this study are commented as well.

Kinetic and Products Study of the Atmospheric Degradation of trans-2-Hexenal with Cl Atoms

“…Y SOA for the T2H + Cl reaction has been found to range between 5 and 38%. These values are found to be higher than the results obtained for the Cl reaction of trans -2-pentenal, which were in the 1–7% range, 25 and trans -2-methyl-2-butenal, which were between 0.3 and 1.7%. 41 SOA yields in the range of 7 to 36% 53 were obtained for the reaction of Cl with isoprene being these SOA yields more similar to the values determined in the present work for the reaction of Cl with T2H.…”

“…Indeed, due to the high sampling flow rate of the FMPS, it cannot be directly connected to the 16-L chamber. This system was previously used in the study of the T2P + Cl reaction by Grira et al 25 …”

“…From the slope of M SOA versus T2H consumption (Δ[T2H]) plots, as shown by eq 3 , the SOA yield ( Y SOA ) can be determined. Both M SOA and Δ[T2H] were corrected as described in previous works, Antiñolo et al 46 and Grira et al, 25 taking into account k L,T2H , and k L,SOA . …”

“… a This work. b Average of Atkinson et al, 23 Grosjean et al, 28 Kalalian et al, 29 and Grira et al 25 ( Table S3 ). c Average of Grosjean et al, 30 Cabañas et al, 31 Zhao et al, 32 Kerdouci et al, 33 and Rayez et al 34 ( Table S3 ).…”

“…While the rate constants of the oxidation reaction of T2H with OH radicals, O 3 , and NO 3 radicals have been reported in several previous works, 20 − 23 , 25 , 28 − 35 the reactivity of T2H with Cl atoms has been scarcely studied. To the best of our knowledge, the only experimental study is from Rodríguez et al 36 who studied the kinetics at room temperature and atmospheric pressure (air or N 2 ) using a relative method and found a rate constant of (1.92 ± 0.22) × 10 –10 cm 3 molecule –1 s –1 .…”