A SACM/CT study of the FC(O)O+FC(O)OO -> FC(O)OOO(O)CF, FS(O-2)O+FS(O2)OO -> FS(O-2)OOO(O-2)SF, FC(O)OO + FS(O-2)O -> FC(O)OOO(O-2)SF and FC(O)O + FS(O2)OO -> FC(O)OOO(O-2)SF recombination reactions and their reverse dissociation processes was performed. The electronic energy along the reaction pathways was calculated at the G3S(MP2)//B3LYP/6-311+G(3df) level of theory. The respective high pressure rate coefficients obtained at 298K are 3.2 x 10(-12), 4.3 x 10(-13), 8.5 x 10(-13), 1.1 x 10(-12) cm(3) molecule (-1) s(-1). The first calculated value compares very well with the available experimental one. From the corresponding thermal dissociation rate coefficients, lifetimes of about 170 days, 4 days and 1 min are predicted for FC(O)OOO(O)CF, FC(O)OOO(O-2)SF and FS(O-2)OOO(O-2)SF. (C) 2014 Elsevier B.V. All rights reserved.