Kinetic and mechanistic study of the gas-phase reaction of CxF2x+1CHCH2 (x=1, 2, 3, 4 and 6) with O3 under atmospheric conditions.

ABSTRACT

The relative-rate technique has been used to determine the rate coefficient for the reaction of CxF2x+1CHCH2 (x = 1, 2, 3, 4 and 6) with ozone at (298 ±â€¯2) K and (720 ±â€¯5) Torr of air by FTIR (Fourier Transform Infrared Spectroscopy) and by GC-MS/SPME (Gas Chromatography-Mass Spectroscopy with Solid Phase Micro Extraction) in two different atmospheric simulation chambers. The following rate coefficients, in units of 10-19 cm3 molecule-1 s-1, were obtained (3.01 ±â€¯0.10) for CF3CHCH2, (2.11 ±â€¯0.35) for C2F5CHCH2, (2.34 ±â€¯0.42) for C3F7CHCH2, (2.05 ±â€¯0.31) for C4F9CHCH2 and (2.07 ±â€¯0.39) for C6F13CHCH2, where uncertainties represent ±2σ statistical error. The atmospheric lifetime of CxF2x+1CHCH2 due to reaction with ozone was estimated from the reported rate coefficients. Additionally, the gaseous products formed in these reactions were investigated in the presence of synthetic air simulating a clean atmosphere. Perfluoroaldehydes, CxF2x+1C(O)H (PFALs), formaldehyde, formic acid and CF2O were identified as reaction products in the investigated reactions. The identified products made possible to propose a reaction mechanism that justifies the observed products. The atmospheric implications of these results are discussed in terms of the potential contribution of the atmospheric degradation of these species to PFAL and PFCA burden.