Calculations on FC(O)OF, FC(O)OOF, and FC(O)OOC(O)F are reported at the B3LYP/6-31+G(d)//B3LYP/6-31+G(d)+ZPC level of theory. All these molecules are predicted to exist as mixtures of rotamers. For FC(O)OF, the calculations reproduce the known structural parameters, the enthalpy difference between the rotamers, the activation energy for their interconversion, and their vibrational frequencies. They predict an O−F bond dissociation energy of 28.7 kcal/mol in the lowest-energy (trans) rotamer. For FC(O)OOF, the calculations predict nonplanar molecules, with O−F and O−O distances of 1.446 and 1.394 Å, respectively, and O−F and O−O bond dissociation energies of 30.8 and 22.3 kcal/mol, respectively, in the trans rotamer. Calculations on FC(O)OOC(O)F reproduce the known structural parameters and vibrational frequencies; they predict an O−O bond dissociation energy of 14.8 kcal/mol. Enthalpy changes for the proposed reactions which lead to the formation of FC(O)OF from FC(O)OOC(O)F and for the proposed decomposition of FC(O)OOF are also calculated.