Theoretical evidence for the formation of perfluorocarboxylic acids form atmospheric oxidation degradation of fluorotelomer acrylates.

The atmospheric oxidation degradation of fluorotelomer acrylates (FTAcs) has been proposed as a potential source of perfluorocarboxylic acids (PFCAs) in remote locations. In this paper, detailed reactions of the main oxidant OH radicals with 4:2 FTAc in the atmosphere have been investigated by using density functional theory (DFT) calculation. All possible pathways involved in the oxidation process were presented and discussed. Based on the mechanism, transition state theory (TST) was used to predict the rate constants of the key elementary steps including the initial reactions of OH radical with n:2 FTAcs and the subsequent reactions of the main intermediates. Studies show that the reaction processes of OH radical addition to C = C bond are dominant and the fluorotelomer glyoxylate and formaldehyde are the major products. At 296 K, the calculated overall rate constant of 4:2 FTAc with OH radical is 1.19 × 10-11 cm3 molecule-1 s-1 with an atmospheric lifetime of 23.3 h. In the atmosphere, fluorotelomer glyoxylate will continue to be oxidized, which will lead to the formation of PFCAs ultimately. In addition, atmospheric reactions of more carbons FTAc (CnF2n+1CH2CH2OC(O)CH = CH2, n = 6, 8, 10) are also discussed in the presence of O2/NOx.